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Peter De Smidt
24-Feb-2012, 12:37
DIYS (Do It Yourself Scanner—pronounced like ‘dice’)--Light Source Thread

Frank Pertronio started this project by suggesting that someone come up with an affordable and contemporary drum scanner, as there is currently huge gap in price and quality between consumer and professional scanners. Domaz suggested using APS-C sensors and using them to take samples of the film, similar to what Gigapan does with large stitched mosaic images. This lead to talk about making a copy stand scanning system using a dslr, a light source and a movable negative stage. Both horizontal and vertical prototypes have been made, or are in the process of being made.

The original thread (http://www.largeformatphotography.info/forum/showthread.php?84769-Making-a-scanner-with-a-DSLR) has become very long and unwieldy. As a result, I’m creating some new specialized threads for future project development.

The new build threads are:
Camera-Supports-and-Positioning (http://www.largeformatphotography.info/forum/showthread.php?87537-DSLR-Scanner-Camera-Supports-and-Positioning),
Lenses (http://www.largeformatphotography.info/forum/showthread.php?87538-DSLR-Scanner-Lenses),
Negative-Stages (http://www.largeformatphotography.info/forum/showthread.php?87539-DSLR-Scanner-Negative-Stages),
Light Sources (http://www.largeformatphotography.info/forum/showthread.php?87536-DSLR-Scanner-Light-Sources),
Stitching-and-Blending-of-Images (http://www.largeformatphotography.info/forum/showthread.php?87540-DSLR-Scanner-Stitching-and-Blending-of-Images),
Cameras-and-Camera-Control-Software (http://www.largeformatphotography.info/forum/showthread.php?87541-DSLR-SCanner-Cameras-and-Camera-Control-Software).
Workflow (http://www.largeformatphotography.info/forum/showthread.php?87545-DSLR-Scanner-Workflow).

These threads are only for positive contributions to the development in the area in question. The project may not succeed, but we’re going to find that out by trying it. But we are not unkind. As the original thread showed, some people have an overpowering urge to say negative things about the project. I’ve created a thread just for this purpose. Please post your negative comments about the project here (http://www.largeformatphotography.info/forum/newthread.php?do=newthread&f=17).

I would like to thank everyone who makes, or has made, a positive contribution to this project!

I'll be summarizing the posts from the original thread about light sources here soon.

Peter De Smidt
24-Feb-2012, 14:56
The light source can range from diffuse to a collimated point source. Nathan Potter has pointed out that the latter might allow higher resolution and contrast. Ideally, the source has a high CRI, i.e. it's as similar to standard daylight as possible, high brightness and low heat. It could be based on flash, LED, plasma, fluorescent, or incandescent source.

My first Light Source Prototype 1 (LSP-1), a diffusion source, looks like:
http://i955.photobucket.com/albums/ae37/peterdesmidt/LSP1_NoLight.jpg

http://i955.photobucket.com/albums/ae37/peterdesmidt/LSP1_LED.jpg

http://i955.photobucket.com/albums/ae37/peterdesmidt/LSP1_Flash.jpg

http://i955.photobucket.com/albums/ae37/peterdesmidt/lightsourcedrawing.jpg

I had some trouble with evenness, and so I move on to LSP-2, which is based off of a De Vere light mixing box for a color head for a 504 enlarger.
Unlike LSP-1, there's not a 45* panel opposite the light source. Instead, the "reflector" panel is at a much smaller incline, just enough that on the end opposite the light source the reflector comes up exactly the to the level of the opening through which the light enters the box. The idea, I expect, is to spread the light from the source over as much of the reflector as possible. The De Vere uses a profiled piece of diffusion plastic to even out the light. Instead of that, about 1 inch above the high point of the reflector sheet, I put a sheet of diffusion. Another inch up (or so) there's the final sheet of diffusion plastic. The lighted opening is bigger than before, and I've fixed everything in place, so that the whole apparatus can't shift when I attach the flash.

Some time soon I'll add some pictures and a diagram.

An interesting high CRI led source is: http://www.cree.com/products/modules_lmr4.asp

Brian Miller suggested that we could take a picture of the light source without film and apply it as a differential map to the image files. This would potentially even out the response from non-perfect source.

Peter De Smidt
24-Feb-2012, 15:14
http://i955.photobucket.com/albums/ae37/peterdesmidt/LSP-2.jpg

Drew Wiley
24-Feb-2012, 16:50
Why not just use a colorhead with its own diffusion chamber? This was done for copy work
in days of yore. An additive head would be preferable, one with feedback circuitry to keep
the illumination level constant. Color quality and the ability to fine-tune it would be superior
to any conventional light source. The trickier part of this is "low heat". There are ways to
do this, but a bit complicated. Not simply a matter of a fan. Or just project the light from
an enlarger, thru the image onto your capture device. Or an HMI source if one of these
turned up used at reasonable price. LED's are still pretty bad for color quality, way behind
color matching fluorescent tubes which can be found up to CRI 98.

Peter De Smidt
24-Feb-2012, 16:59
As you say, heat is the reason that I don't use my color heads. And in the De Vere's case (I have a De Vere and a Philips color head) vibration due to the fan would be an issue.

Vibration and heat would be less of an issue with a horizontal configuration, ala Mr. Denney's approach.

The LED module I linked to earlier is available in a module that has a CRI of greater than 90.

Drew Wiley
24-Feb-2012, 17:14
I'm rather interested in how these LED and CFL sources evolve, but mainly from a print
display standpoint, particularly since they are now required by local bldg codes in commercial applications. Not happy about that, but hopefully the display market will drive
better color performance. Getting a lightbox to even out might require more than a diffuser.
Multiple diffusers help but also reduce illumination as the Lambertian factor goes up, and
also affect color temp. One secret weapon I have found is called a linear array fresnel
(completely different animal from a conventional fresnel), which will diffuse far more evenly
with less loss than simple frosted panels, but at greater cost.

Peter De Smidt
24-Feb-2012, 17:46
I wasn't able to find any pictures of that type of linear array Fresnel with a brief search. Is it similar to the type of add-on diffusers that were available for something like a Vivitar 283 flash? I have a set with ones of various colors. The have a grid like array of small pyramids on them.

jon.oman
25-Feb-2012, 07:32
It would be nice for theses threads to be made 'sticky'.........

Mike Anderson
25-Feb-2012, 19:16
It would be nice for theses threads to be made 'sticky'.........

Or just a master index thread with links to the others to not take up so much room at the top.

AJSJones
8-Mar-2012, 21:07
Just noticed this set of threads!
I have a Rosco LitePad 6x6 and it is described as ~6000K with a CRI of 93 (http://www.rosco.com/canada/images/LitepadthetrphotoCDN1.pdf). I put a 3mm sheet of "white" plastic from TapPlastics (eyeballed as "neutral") as a diffuser and got very nice uniformity of both luminance and chrominance. I don't know how to measure CRI but I do have an IT8 from Agfa from years ago - it's piece of 35mm slide (shot with a Canon 5D2 and 100 macro). With an image of only the litepad, the values of a full exposure were from 240-251 in all three channels after WB on the middle of gray wedge. See the image below. I'm sure I can build a profile out of this :D The whole thing sits on a XY positioner (here (http://www.ebay.com/itm/4W-Macro-Focusing-Rail-Slider-Quick-Release-Plate-K0G-/160637691388?pt=AU_TripodsMonopods&hash=item2566c0a5fc#ht_3757wt_1141)is an example). The litepad has a bubble level (it stays centered as the XY go through their range) and the camera a double bubble, but I've not measured anything yet.
I have just started playing with combining exposures as per this tutorial, (http://jtrujillo.net/qpix/) as an early attempt to get the shadow noise down and it works well. Just need to set up an action that reproducibly combines each pair into one before stitching them together.
I have not finished the project but it seems on track so far, and I thought I'd share some info now. If I finish it, I will write it up a bit more.... (and maybe put the various parts in the appropriate threads)
http://www.fototime.com/FFDF6638FC4F455/standard.jpgLarger version is here (http://www.fototime.com/FFDF6638FC4F455/orig.jpg)

Peter De Smidt
8-Mar-2012, 21:59
The Rosco LitePad looks interesting. A 3"x3" version is about $50. The main thing will be if you get enough light. With a continuous light exposure, we probably want to avoid shutter speeds from about 1/15th of a second down to a second, as these are the most susceptible to vibration.

Near the beginning of the main thread, I showed a stepwedge photographed with a dslr+macro lens made with one exposure, and one with blended exposures. There are certainly gains to be had there, if needed. While most bw negatives would fit within the dynamic range of one exposure, I just scanned a tech pan negative with no problems, digital images are noisiest in the shadows, and with bw negatives this means that the noisiest areas will be the highlights when the image is inverted. As a result, some type of multi-exposure blending could be very useful, especially in images with lots of very delicate highlights.

AJSJones
8-Mar-2012, 23:13
I use mirror lock-up and 10 sec timer - my camera stand is not the greatest and exposures are indeed down in that range where I'd normally do that for taking pictures. I blended a 1 sec exposure with a 1/15 sec exposure and that dramatically reduced the shadow noise on the test (from a Provia 4x5 slide where the highlights were just not blown in the DSLR and were almost, but not quite blown on the slide). The result was way better dynamic range than a single scan from my AgfaScan Duo T2500 that broke down, and the detail captured depends on how many shots I stitch - I can get it all with about a 12 shot stitch, possibly fewer. That was the next stage in the project...

Peter De Smidt
8-Mar-2012, 23:25
Sounds good. I haven't down any work with slides yet.

rdenney
30-Mar-2012, 14:17
Well, I had a "duh!" moment, or two.

I reported last week that I had had no luck with the slide projector as a light source. I was giving a presentation in another city this week, and looked into the projector light, and, well, DUH!, it was a pinpoint of light. So, I think to use the projector as a source, it needs to be a good distance away (to make it as much a pinpoint as possible), and then a condenser needs to be close to the film, maybe right behind it. Well, DUH!, that's the way condenser enlargers do it. I had thought the condenser in the slide projector would be adequate to achieve that, but (1) it's not nearly enough of a condenser and (2) it's small and close to the bulb. When looking into the front of the (turned-off) projector, I can see the ELM bulb reflector in its entirety. And the condenser is too weak. It really does need to be a point source with enough of a condenser to collimate the light.

So, in response to the above, I looked into the Rosco Litepads. For $50, the 3"x3" panel looked interesting. Then, when perusing reviews of it, someone commented that it looked like the standard LED back-light arrangement for computer monitor.

Well, DUH! I have computer monitors hanging from the ceiling. So, I took my work laptop, which has a very bright LED backlight, and set it on edge behind my negative carrier, opened Notepad and maximized it to get a white display (or white enough for testing), and made some tests. And the tests look a lot better. I'm strongly tempted to task an old computer to displaying a fall-off correction pattern on the screen of an old monitor.

At the f/11 that works best with my best lens, I get about 3 or 4% falloff with an exposure of about half a second. I suspect the fall-off is sensor-related--the falloff pattern looks the same on all lenses, being a little off-center no matter how I position the monitor panel.

I learned a little about my lenses, too--in the lens thread. And I learned a little about sharpening and the effects of the anti-aliasing filter, also in the lens thread.

Rick "not quite ready to attempt stitching just yet" Denney

Peter De Smidt
30-Mar-2012, 14:29
Sounds like you're making some good progress.

peter ramm
31-Mar-2012, 09:03
Rick, have you considered trying this type of LED back light?

http://www.edmundoptics.com/products/displayproduct.cfm?productid=3358

Can't remember if it has come up here or not. They work pretty well imaging film, if you can live with the wavelength emission. We played with these and with fiber optic plates trying to get even lighting. In the end, we used a custom fluorescent that we had on hand anyway.

Otherwise, looks like you are heading towards Kohler with the projection system.

Peter De Smidt
31-Mar-2012, 09:25
Those are nice but a little pricy, and I wish they listed a CRI rating. Daniel has been investigating a similar, and much cheaper, approach. His current panel should work well for BW, and a high cri panel is in the works.

With continuous lighting, we really want to avoid exposure times in the 2-1/15th of a second range, as those are most susceptible to vibration.

Note that a very experienced coin photographer has found that using a canon model with an electronic first curtain shutter significantly helps with image sharpness even at a low 1x magnification. For more on Canon's low vibration shutter, see: http://krebsmicro.com/Canon_EFSC/index.html

rdenney
31-Mar-2012, 13:34
Rick, have you considered trying this type of LED back light?

A little pricey for me, too.

But I'm sorta liking the idea of using a computer display, because of the possibility of projecting a correction pattern on it. And the correction pattern can be made by inverting a photo with no negative in the stage and displaying it at the appropriate size on the display used for illumination. Should be able to dial in perfect illumination.

It does not solve the problem of shutter speeds in the danger range. My Canon doesn't have the electronic first curtain, but the opening curtain makes no discernible movement that I can detect. It's a custom function on my camera to turn the self-timer into a timer that raises the mirror, waits three seconds, and then releases the shutter. I see no indication of camera movement as a cause of fuzziness.

Instead of setting a laptop on edge, I need to take a spare monitor and do something a little more stable and repeatable, so that I can experiment further. For a diffused light source, though, I think this is the way to go.

For a collimated source, that's another matter. There, I think an enlarger head is the cheap way to go. But I'm not yet motivated to dig that deeply in my storage room--I know how many "might as wells" will be attached to that effort, unless I do it on the sly, which isn't easy.

I also need to experiment with exposure levels. I've been photographing to put the peak in the middle of the histogram, which is fine for negatives, but which may exaggerate lighting variability when photographing the light source without a negative. I will eventually need to set the exposure to just sit under 255 (on an 8-bit scale) with no negative, or, at most, through film base+fog. That will provide the maximum dynamic range, I think.

Rick "whose experiments are continuing" Denney

ludvig friberg
22-Apr-2012, 10:32
Perhaps this is making it more complicated that it needs to be, but if we use a flying spot perhaps with a white laser or a fast smooth wipe with a line laser we would get rid of flaring. I have no idea how difficult or expensive that would be. But In a way it would turn the areasensor in the dslr to a linesensor.

Ludvig

rdenney
22-Apr-2012, 16:33
Perhaps this is making it more complicated that it needs to be, but if we use a flying spot perhaps with a white laser or a fast smooth wipe with a line laser we would get rid of flaring. I have no idea how difficult or expensive that would be. But In a way it would turn the areasensor in the dslr to a linesensor.

Ludvig

Yes, I think that would be best. But now we'd have to have two movement apparatuses, one for the film and another for the laser. And the laser apparatus would have to be tightly controlled at the resolution of the scan, and also constrained by an aperture. Very soon, we are at the mechanical complexity of a drum scanner, which works similarly.

We need to be sure that our diffusion sources are truly limiting before it would seem worth trying something else, and then we should try to concoct a proper collimated source. Those are much cheaper and easier alternatives, it seems to me, and cheap and easy are objectives given that people will probably have to build their own.

Rick "back in travel mode and having to delay further progress for a while" Denney

Peter De Smidt
22-Apr-2012, 19:08
We need to be sure that our diffusion sources are truly limiting before it would seem worth trying something else, and then we should try to concoct a proper collimated source. Denney

I agree.

ludvig friberg
23-Apr-2012, 01:52
Yes all that make a lot of sense. If one used a a computerscreen as backlight as I have seen some interest for one could at least easily try it by drawing a white line one pixel row at a time. It could be interesting to try I am just throwing some ideas around

Peter De Smidt
23-Apr-2012, 09:25
Throwing ideas out there is a very good thing! Even if it's something the people don't check out immediately, it could turn out to be very useful down-the-road.

ludvig friberg
24-Jun-2012, 06:46
I have built a lightbox for flash. It works ok and is almost even but I am having trouble getting anything larger than 40x40mm even with my design. Ideally I would want something bigger so I can use the same backlight for full frame captures of a 6x7 negative or slide. Then If I need to i just move the camera closer and take a series of tiles. I started to look at dichroic light boxes. Could thhese be altered to have a flash as a lightsource?

What would be the best way to get a flash like speedlite really even across 6x7 is the question I guess.

Peter De Smidt
24-Jun-2012, 07:20
I based my source on a De Vere light mixing box. The lighted area is approximately 250mm x 250mm.

Nathan Potter
24-Jun-2012, 07:45
I have built a lightbox for flash. It works ok and is almost even but I am having trouble getting anything larger than 40x40mm even with my design. Ideally I would want something bigger so I can use the same backlight for full frame captures of a 6x7 negative or slide. Then If I need to i just move the camera closer and take a series of tiles. I started to look at dichroic light boxes. Could thhese be altered to have a flash as a lightsource?

What would be the best way to get a flash like speedlite really even across 6x7 is the question I guess.

ludvig, I think you would need what is commonly called a beam expander. It would be a simple condenser lens, or set, at some distance from the flash face - say a few hundred mm - and a diameter sufficient to easily cover the largest size image frame you are likely to use. The condenser set from a 4X5 D2 enlarger comes to mind. That condenser is a pair of convex/plano 150 mm diameter lenses face to face. This set might be placed 100 to 200 mm from the face of the flash; you'll need to experiment a bit with this. Also you will have to work on the uniformity of the light hitting the film. The further the condenser is from the flash the more even the light but the lower the intensity.

A second approach without using condensers is to just increase the distance between the flash and the film. I do this by bouncing the flash off a white card which sits at a 45 degree angle right under the film. The flash is at the end of a cardboard tube about 1 meter away from the white card. The white card is a good diffusion source so reduces the dust and particle imaging compared to the condenser technique.

Nate Potter, Austin TX.

ludvig friberg
24-Jun-2012, 11:59
I googled quite a bit and could not find a good description on how a de vere box is constructed. It seems to involve two lightsources and a mirror plus some diffusor? Do you have a picture I could look at?
I am looking into a good way to do the flash at a distance but the best would be to have it a bit more compact than 1 meter away!

Thanks for the suggestions.

Peter De Smidt
24-Jun-2012, 15:26
Ludvig,

I'll take some pictures soon, both of a De Vere unit and of my light source.

Serge S
30-Jun-2012, 10:04
Why can't we just adapt a standard lightbox previuosly used for viewing slides as a scanning platform mated together with a simple copy stand. They are color calibrated with a decent CRI number.

Previously, I had purchased a couple of Bowen Ilumitran side dupers used on ebay with the idea of using it to scan (with a DSLR), but never got around to setting it up.

Peter De Smidt
30-Jun-2012, 11:34
Why can't we just adapt a standard lightbox previuosly used for viewing slides as a scanning platform mated together with a simple copy stand. They are color calibrated with a decent CRI number.

Previously, I had purchased a couple of Bowen Ilumitran side dupers used on ebay with the idea of using it to scan (with a DSLR), but never got around to setting it up.

Standard light boxes aren't ideal for two reasons. First, most have very noticeable hot spots. My Porta-Trace one certainly does. Second, at these magnifications vibration can be a real problem. If you have a Canon with the EFSC shutter mode (See: http://krebsmicro.com/Canon_EFSC/index.html), then you can probably do what you like, but if you don't have that super-low vibration shutter, then you probably want to avoid timed exposures in the 1 second to 1/15th of a second range. Using flash correctly minimizes the problems with vibration, but there might be issues with consistency, although that hasn't been a problem for me so far.

Serge S
30-Jun-2012, 13:43
Standard light boxes aren't ideal for two reasons. First, most have very noticeable hot spots. My Porta-Trace one certainly does. Second, at these magnifications vibration can be a real problem. If you have a Canon with the EFSC shutter mode (See: http://krebsmicro.com/Canon_EFSC/index.html), then you can probably do what you like, but if you don't have that super-low vibration shutter, then you probably want to avoid timed exposures in the 1 second to 1/15th of a second range. Using flash correctly minimizes the problems with vibration, but there might be issues with consistency, although that hasn't been a problem for me so far.

Thanks Peter. I am planning to upgrading to the 5D2 at some point. I see that it has that shutter you are referencing:)
Sounds like the Illumitran Idea was not half bad, as it is electronic flash

rdenney
30-Jun-2012, 16:27
I just managed to score a nice Illumitran, with the contrast device. I'm thinking a mirror might be a useful thing with that and my setup. I'll know more when it arrives.

Rick "who recently put eyes on some old work with 35mm Kodachrome that will see action again" Denney

ludvig friberg
1-Jul-2012, 05:28
The uneveness is not a big issue at least not for me. I have done some testing where I take a picture of the lightsource and use to divide the uneveness from the lightsource. This also takes out any vignetting and dust on sensor. If I have a piece of the film with no exposure I can also divide out all colorshifts from the lightsource in combination with the orange mask. I haven't tested how important CRI is yet. I have one some exposures with a Canon speedlite flash and some LED sources but I don't know the CRI rating of any of them. Xenon bulbs is far from perfect I believe and LED even worse most of the time. I get pretty decent results anyway. I am going to try out sunlight when it stops raining and see if there is any big difference. Sunlight of my test neg should provide a nice perfect reference. I have looked at some new halogen bulbs called solux that have a very good CRI and are used by kodak in the Pakon line of scanners.

Peter De Smidt
20-Jul-2012, 08:25
On an email list, Ernst Dinkla, a very knowledgeable scanner, printer and tinkerer, said that with BW film his Coolscan does best using only the blue LED. (Using Vuescan he can turn off the red and green leds.) He theorized that due to the shorter wavelength the scanner could capture more detail than when using all of the leds. He posited that with a dslr scanner using green light for BW film might be best, as most dslrs have twice the number of green sensors than blue or red, and it would avoid the longest wavelength, i.e. red. Since I wanted our scanner to work in color, I've been working with a white source. I also thought that getting info to all of the camera's sensors might be a good idea, but Ernst's idea is definitely worth looking into for BW scanning.

ludvig friberg
20-Jul-2012, 16:12
I have done quite a lot of testing on color neg lately. I have tested different LEDs, flash, sunlight, tungsten in my dslr scanner up against a hand tuned scan in Nikon coolscan 8000ed. With handtuned I mean I have dialed in the orange mask by changing the exposure of the red, green and blue LEDs in the scanner to get the best possible AD conversion from the sensor. This is my gold standard right now. I get pretty good separation between the cyan, magenta an yellow inverse dyes from the Nikon butI have never scanned on anything better than the NIkon so I dont know how good separation I should try to achive. I have no idea what wavelenghts the leds in in the 8000ed has but I assume it is as wide as possible to cover the very varying dyes in different films.

The conclusion of my tests so far is that tungsten is by far the best artificial lightsource for negative color film. This is quite obvious if you think about it, tungsten is full spectrum so it covers all parts of the dyes. With the LED and flash I get much poorer separation between C,M and Y. It is of course much to warm(Kelvin) so I use full CTB filter, this takes a lot of light so I need a lot of Watt. Either that or one exposure for the red channel and another one for the green and blue. Probably I will need something like 1500 lumen from the lightsource. I will have a relay so it turns the light on only for a second or so when its exposing. Also any fans will turn off a second before exposure. And then dimmed for setting focus and general setup, the live view autoexposes and shows a nice image with some more iso and full aperture. I will try in the future to do the Infrared too and then tungsten is very handy, lots of IR is emitted.

Another solution I have looked at is seperate leds in a matrix and a diffusor. Either rgbleds plus IR or led in a pattern of: red, blue, green, IR, red, blue etc. Here you have to really choose your wavelenghts with precision I think most leds are quite narrow.

This one is a cheap and very customizable platform for something like this.

http://evilmadscience.com/productsmenu/tinykitlist/75

or this one for a smaller lightsource like mine
http://evilmadscience.com/productsmenu/tinykitlist/157

I have built the first stage of motion now and I have solved all the programming and control of the machine. Are working on the negative holder now, waiting for parts to finish the stage.


best regards

Ludvig

Peter De Smidt
20-Jul-2012, 16:58
It's great to hear about your progress, Ludvig. Nice work! Are you using an Arduino to control the motion? (Although we should probably switch threads if we discuss that aspect of the project.)

Daniel Moore
21-Jul-2012, 11:44
Very exciting developments, Ludvig. Please tell us more about your design so far.

Peter De Smidt
22-Jul-2012, 19:06
Heat reflecting or heat absorbing glass could be helpful with a tungsten source, ala many enlarger heads. If someone goes this route, using a real enlarger head could be a very viable alternative, especially if they have one laying around.

cosmicexplosion
23-Jul-2012, 03:43
i have absolutely nothing to contribute to this fred, except maybe a bit of cheering from the side, GO YOU MAD BASTARDS!!!!!

Peter De Smidt
23-Jul-2012, 08:17
:)




.

David_5527
21-Oct-2012, 13:09
Hi. Has anyone tried using a large computer screen? I have an Apple 27"that gives off a lot of even light. I am trying to figure out a way to do cheap scans of my 14x17" negs before I make expensive scans or platinum print.

It seems like the issue will be to get it a bit away from the screen, so you dont see the screen pixels...anyone trying this?

David_5527
22-Oct-2012, 00:24
Actually, my computer screen is just shy of 14", so wont work...oh well....other sources?

Amedeus
22-Oct-2012, 00:36
Ludvig,

Getting white out of RGB LEDs is a difficult and expensive proposition if high CRI is a requirement. Getting white with high CRI out of a yellow phosphor driven by a blue or UV LED is equally difficult. You can match the LED wavelengths with the RGB sensor and the rest becomes a matter of software.

Xenon and tungsten are both blackbody emittors/radiators like the sun. When properly driven, Xenon is closest to sunlight and is preferable when a lot of blue is required. Xenon flashes are driven by very short high current pulses and as such the color temperature is often too high (lack of red, overdose of blue) and the latter doesn't necessarily match with a digital sensor.

Evenness is easy to deal with through holographic diffusers if the light source is not tooo hot ;)

I'm the CTO for a lighting company dealing with LED and Xenon with quite a few applications crossing over in photography lighting ... I'm open to specific questions.


The uneveness is not a big issue at least not for me. I have done some testing where I take a picture of the lightsource and use to divide the uneveness from the lightsource. This also takes out any vignetting and dust on sensor. If I have a piece of the film with no exposure I can also divide out all colorshifts from the lightsource in combination with the orange mask. I haven't tested how important CRI is yet. I have one some exposures with a Canon speedlite flash and some LED sources but I don't know the CRI rating of any of them. Xenon bulbs is far from perfect I believe and LED even worse most of the time. I get pretty decent results anyway. I am going to try out sunlight when it stops raining and see if there is any big difference. Sunlight of my test neg should provide a nice perfect reference. I have looked at some new halogen bulbs called solux that have a very good CRI and are used by kodak in the Pakon line of scanners.

Daniel Moore
22-Oct-2012, 00:36
David, admittedly, this is off the top of my head, but I'd think about stitching flatbed scans for this size. It could be possible to find a sheet of anti newton ring glass to prop up the neg to about the right height off the table, and perhaps another on top to sandwich it and keep it flat.

Daniel Moore
22-Oct-2012, 00:46
Amedeus, many of us have spent a good deal of R&D dollars (given that Time=Money : ) looking for a high CRI/high EI solution. You are in a unique position to comment on this. What would you chose personally?

Amedeus
22-Oct-2012, 01:33
Let me ask some boundary condition questions first:

Area to light ?
Sensor technology ?
Line sensor or area sensor ?


Amedeus, many of us have spent a good deal of R&D dollars (given that Time=Money : ) looking for a high CRI/high EI solution. You are in a unique position to comment on this. What would you chose personally?

ludvig friberg
22-Oct-2012, 03:17
To David:

I have built a setup to make digital "contact sheets" of all my archive of negatives. These are mostly 120 film in A4 plastic sheets. I used a 24inch screen for this with a diffusion filter, the type used on lights usually bought on wide roll. I had a small part of the screen not covered in diffusion. In this square I had a number displayed, this way I could easily index all my old negatives. It was 10+ binders full of negs, thousands of exposures. I managed to get digital contacts of them all in 2 days. Took a few seconds per sheet. I just have the raw files and a negative lightroom setting, works fine for preview and was MUCH faster than any scanning method.

Ludvig

ludvig friberg
22-Oct-2012, 03:26
CRI not important? Finding and matching sensors sensitivity to r, g and b respectively better?

I have done a lot of test on negative color film and my best results so far comes from RGB LED. I can easily dial in whitebalance for the negative and further getting the best separation between the CMY layers. It seems to me that the sensor has a much broader sensitivity around each of the r, g and b. Leds seem to be often VERY narrow in their color.
But still, the camera only sees the world as red, green and blue. And to me this seems to be the best way.

Also please tell me more about holographic diffusers!

Daniel Moore
22-Oct-2012, 09:35
For several reasons I think illumination to cover 4"x5" is ideal, it's the smaller formats that will benefit most from this project. The capture device will be a DSLR so in all likelihood a CMOS sensor. Since there is no single widely accepted design as yet, both stationary and moving light (integrated light and negative carrier) sources are viable. Favor given to higher shutter speeds if possible.

Peter De Smidt
22-Oct-2012, 10:17
My light source currently has a light emitting area of 4.25" square. I wouldn't want to go smaller than that.

Amedeus
22-Oct-2012, 22:31
OK, read a few posts deeper in this project and I'm getting it ... "scanning" negatives with DSLR rather than with a scanner. So you gain processing speed and there are quite a few DSLR's out there that will beat scanners in IQ and definitely in processing speed ;-)

RGB LEDs are indeed narrowband light sources, average ~ 30nm and the CMOS or CCD sensors of DSLR or digital backs to have a significant wider spectral performance and that is how the internal software of the camera is adjusted for. This said, it is possible to get good to decent performance with RGB LED and CMOS sensors if one can adjust the curves a bit ;-) ... this is what happens in cameras or post processing software anyhow when one corrects for different CT's and even different spectral performance for mercury based lights (fluorescent, mercury-vapor or HMI)

It's even possible with RGB lasers to create a white light suitable for full color projection and the bandwidth is only 2-3nm per wavelength. Not claiming the CRI is perfect but the eye can be fooled.

While LED's have equally a challenging CRI proposition but some manufacturers get creative and mix warm white (~3200K) and cool white (~5000K) together to create a more pleasing blend by dynamically adjusting the current for each sector. In some cases cyan/green/red LEDs are added to ensure sufficient CRI performance. Keep in mind that the average white LED has peaks in blue and yellow and green/red performance is not too stellar.

Brings us to the next challenge ... blending it all together. Space and diffusers are your best friend. You will be loosing intensity but gain intensity and color uniformity. There is no magic bullet that offers it all, just the plain nature of physics. Some LCD backpanels are doing a decent job on first sight but as soon as you remove the LCD you'll find out that uniformity kinda sucks. There is just not enough space in an LCD sandwich to create great diffusion without throwing most of the light away.

Fast shutter speed ? This translates to lots of light and that in turn requires more power feeding the LED's and at that point you have to keep an eye on the thermal performance of the LED. Although the latter don't produce any IR out of the front, they produce a decent amount of IR out of the back and that needs to be dissipated one or other way. If not, the LEDs will become less efficient (droop) and you'll have to deal with a color shift ... more so for while LEDs.

It's of course all possible but will require choosing the correct operating point/compromise for the application. Brightness, uniformity, size, cost ...

I'm personally somewhat familiar with the immediate challenges as I've built on multiple occasions diffuse light sources to illuminate CCD and linescan sensors during their calibration cycle, so "perfect" uniformity was high on the list of desirable characteristics. In all recent cases a combination of LEDs were used with a plurality of spaced holographic diffusers in a large integrating rod type of assembly (I need to find a link to a company who will supply holographic diffusers to individuals, they are widely used in LCD displays and in LED fixtures ... ) In the days of no suitable LED's, we would use tungsten lamps to achieve same and have the benefit or blackbody CRI performance. Instead of holographic diffusers we used anything from ground glass, milk glass etc ... you name it, we probably tried it. You can use Xenon but it is too much of a point source to diffuse easily.

Let me know if I'm way of topic here or misunderstood what you are trying to achieve. So 4x5 makes sense for those wanting to scan 4x5 negatives but the majority will be using 6x6, 6x7, 6x8 and 6x9 format ... 35mm can use same also ... of course ;-)

Amedeus
22-Oct-2012, 22:34
Also please tell me more about holographic diffusers!

Take a look at http://www.luminitco.com/

Amedeus
22-Oct-2012, 22:41
CRI not important? Finding and matching sensors sensitivity to r, g and b respectively better?



Since RGB LEDs are so narrowband you can generate a tri-stimulus with no overlap when it comes to the sensor part (depends on the Bayer filter on the sensor of course, they are not all created equally)

Without "overlap" one can intuitively see that one can adjust the power to the individual light sources to hit the correct coordinates into RGB space to achieve a wide range of CCT (correlated color temperature ... as we're not taking black body spectral performance here) This is how the laser projections systems work also. Strategically chosen wavelengths to fool the eye we're seeing white. CRI is poor but the eye doesn't seem to mind. Although in the latter cases saturation can be an issue.

If a narrowband light sources stimulates two colors in the CCD/CMOS sensor at the same time then it is much harder to create a clean profile as changing one, affects the other ...

Struan Gray
23-Oct-2012, 02:05
I usually recommend Edmund Optics as a source of optical components for individuals buying lots of one. Not only are they willing to deal with individual amateurs, but they do so in a professional and friendly way. It's always worth checking their surplus outlet, Anchor Optics, to see if what you want is available more cheaply. For photographic use, the difference between their research grade and commercial grade optics is (almost always) irrelevant.

They have holographic diffusers.

Worth noting though, is that if you are going to scan-and-stitch (rather than shoot the whole neg as a single frame) there are advantages to restricting the illuminated part of the negative to only the part being photographed by the DSLR. Flare will be less, and all your illumination optics become smaller, and so can be cheaper and/or higher quality.

There is a fundamental tradeoff in scanning between diffuse lighting for convenience and minimising the intrusiveness of scratches and dust, and collimated lighting (Kohler illumination, if you can manage it) for maximum sharpness at the resolution limit. These were issues debated ad-infinitum in the days of enlargers, and they are still relevant now. There is no best answer - it depends on your way of working, and your goals.

Finally, the traditional argument against using narrowband light sources is that they make it hard to distinguish subtle colour variations - which for me at least is one of the main attractions of LF). It's the same problem as print metamerism. However, here it becomes a question of calibration, but it might mean that you need to build your LED panel with hardware adjustments of the colour balance, rather than relying only on post-capture software adjustments.

Peter De Smidt
23-Oct-2012, 06:38
<snip.
Worth noting though, is that if you are going to scan-and-stitch (rather than shoot the whole neg as a single frame) there are advantages to restricting the illuminated part of the negative to only the part being photographed by the DSLR. Flare will be less, and all your illumination optics become smaller, and so can be cheaper and/or higher quality. <snip>


I agree, as long as the masking material is between the negative and the lens. The light source, at least with a diffuse source, needs to be much bigger than the area being sample, since otherwise the edges of the negative will get darker than the middle of the frame.

Flash is a viable lighting option. It's been working well for me.

Edmund optics is very good. So is Thorlabs.

Amedeus
23-Oct-2012, 07:46
Flash is a viable lighting option. It's been working well for me.


Xenon flash is definitely a viable option. Takes a little more work/optics to generate a flat illumination field (or overfill the aperture ...) but the key advantage is that the CRI is high and CCT is well defined (mostly blackbody radiation) and software is readily available for correction. Simply built in into the camera or post production. And easy to get short shutter times ;-)

Amedeus
23-Oct-2012, 07:57
There is a fundamental tradeoff in scanning between diffuse lighting for convenience and minimising the intrusiveness of scratches and dust, and collimated lighting (Kohler illumination, if you can manage it) for maximum sharpness at the resolution limit. These were issues debated ad-infinitum in the days of enlargers, and they are still relevant now. There is no best answer - it depends on your way of working, and your goals.

There's a lot going on for collimated lighting of course, the downside is a more difficult set-up and often a higher cost in optics. Definitely a winner in combination with a point source when it comes to obtaining a flat field




Finally, the traditional argument against using narrowband light sources is that they make it hard to distinguish subtle colour variations - which for me at least is one of the main attractions of LF). It's the same problem as print metamerism. However, here it becomes a question of calibration, but it might mean that you need to build your LED panel with hardware adjustments of the colour balance, rather than relying only on post-capture software adjustments.

Agreed with the need for hardware adjustments. Also, there's no need to be limited to 3 LED colors ... Many designers of high CRI LED fixtures utilize 5-6 or even more colors to get the spectral response they need, each with their own drivers and abiltiy to adjust operating current.

Daniel Moore
23-Oct-2012, 10:54
I'm not sure how various colors are created in LED technology (is it really just power?) but how about adding alternating gel filters to an LED array panel such as this Back-lit LED Panel shown further down this page. (http://www.luminousfilm.com/led.htm)?

Is there a way in which a digital capture can be used to analyze an illuminant for spectral information beyond the basic RGB histogram?
Would an image taken of a holographic diffraction grating film (http://www.anchoroptics.com/catalog/product.cfm?id=247) placed over the illuminant be instructive?

Does anyone have a notion on what it would take to wire an array of lower power flash bulbs? Specifically, how to get say 2 or 4 bulbs to agree they are charged similarly? The plan would be to arrive at an averaged output to help rule out exposure variations, while allowing the illumination to be built into the negative stage thus moving with it.

Struan Gray
23-Oct-2012, 12:01
.... there's no need to be limited to 3 LED colors ... Many designers of high CRI LED fixtures utilize 5-6 or even more colors to get the spectral response they need, each with their own drivers and abiltiy to adjust operating current.

That's an interesting idea. It's not as if this project needs another sub-project though :-)

Would an integrating sphere (mixing box for old timer darkroom colour types) make more sense than layers of diffusion if you have that many different colours to even out? It would make it easy to switch between flash and LED lighting if you wanted that.

Struan Gray
23-Oct-2012, 12:25
I'm not sure how various colors are created in LED technology (is it really just power?) but how about adding alternating gel filters to an LED array panel such as this Back-lit LED Panel shown further down this page. (http://www.luminousfilm.com/led.htm)?

LEDs are pretty-well monochromatic, certainly by photography's standards of spectral resolution. What that means is that the spectrum is just a narrow peak centred on a particular wavelength. There are ways of nudging the peak to higher or lower values, but you can't move very far - not far enough to change the apparent colour as seen by the eye - and most commercial LEDs are mounted and packaged so as to prevent this happening as much as possible.

So adding a filter won't shape the spectrum in the way that, say, using a 85B on incandescent light will boost the blue over the reds and yellows. All any filter will do is cut the peak to a greater or lesser extent (including perhaps extinguishing it altogether).

So for colour shifting you tend to combine three or more LEDs with different peaks corresponding to some set of primary colours. The eye-brain system then does the work of turning the three monochromatic peaks into a perceived colour. Varying the intensity of the individual LEDs (usually by adjusting the average current in various ways) allows you to mix the three primaries and create colours in the usual additive colour wheel way.

There are now 'white' LEDs which have a high enough power to then put a filter in front of for spectral tuning. They are made by combining LEDs of different colours exactly as described above (and sometimes a phosphor or two), but in such a way as to create a colour perceived as white. In some ways, the manufacturer has done the job for you, but in a way that cannot be adjusted or altered.



Is there a way in which a digital capture can be used to analyze an illuminant for spectral information beyond the basic RGB histogram?
Would an image taken of a holographic diffraction grating film (http://www.anchoroptics.com/catalog/product.cfm?id=247) placed over the illuminant be instructive?

If you know what you are looking for, just looking at the spray of coloured light from a CD or DVD is instructive. Anything which diffracts relatively evenly across the visible spectrum will do, including those cheesy effects filters which surround streetlights with rainbow stars.

If you want to get into quantitative measurements cheaply there are ways to build cheap spectrometers (a cereal packet and a CD are popular school science projects) for direct viewing with the eye, whose spectrum you could photograph with your camera. Otherwise there are cheap (one-to-several hundred dollars) USB spectrometers which will do the job, or if you have a colour calibration puck for your screen and/or print output some of them have shareware programs available to give you a raw spectrum from their built-in spectrometer.

Often though, interpreting the spectrum is more difficult than obtaining it. This is doubly so if you wish to interpret it in terms of perceived colour rather than scientific spectrum weightings.



Does anyone have a notion on what it would take to wire an array of lower power flash bulbs? Specifically, how to get say 2 or 4 bulbs to agree they are charged similarly? The plan would be to arrive at an averaged output to help rule out exposure variations, while allowing the illumination to be built into the negative stage thus moving with it.

My own tinkering has lead me to the conclusion that it will be easier to build a small area illuminator and move the film through the patch of light it produces, than to create a wide-area light source which is even in intensity and colour. However, there are no rules, and nobody is handing out prizes :-)

Daniel Moore
23-Oct-2012, 13:00
Thanks Struan, great info.

The concept I'm working on is based on a stacked XY sliding mechanism so it would have to carry the light with it, as opposed to an open base/sliding rail arrangement with the light in the center. There is a deluge of LED lights on the market now, some claiming high CRI values and all intended for photography. I wouldn't mind testing some of them if I had a scientifically sound way to do it.

"shareware programs available to give you a raw spectrum from their built-in spectrometer." Do you have one in mind? Still seaching on that one. Being able to determine CRI would be handy.

SURF
23-Oct-2012, 15:40
Spectroscope is the key world. There is a lot and cheap.
http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=spectroscope&rt=nc

Want to add some obvious and not so things:
1. For BW originals color doesn't matter.
2. For negative and positive color originals the color of the light source should be different.
3. It is not obvious that the lamp with the best CRI will be the best for digital camera scans. For me at least.
4. The LCD monitor can be 3-4 stops brighter if the TFT panel is removed. But it is not straightforward task. If the color is OK then it makes a perfect light table.
5. LEDs for LCD panels often are not narrow peaks seen through spectroscope. Fluorescents for LCD are mostly narrow peaks.
6. One of the best high CRI lamps are made of incandescents with blue filter.

Peter De Smidt
23-Oct-2012, 15:52
I'm not so sure that color doesn't matter for BW film "scans". It would be interesting to try different colored sources and compare results. My guess is that green light would be best, but this is the type of thing is best investigated by experiment. I could use Rosco filters (from a swatch book) on my flash as a source.

Another idea would be based on a Philips PCS2000 tri-color enlarger. This one had three halogen bulbs, each with it's own filter; a red, a green and a blue. The intensity of each light could be varied independently of the others. It was a very good setup for printing color, and not bad for VC papers. The only thing I don't like about halogen bulbs is the heat.

Various LED mixes could also be interesting, but the biggest hurdle right now for me is automation.

Amedeus
23-Oct-2012, 16:37
That's an interesting idea. It's not as if this project needs another sub-project though :-)

Would an integrating sphere (mixing box for old timer darkroom colour types) make more sense than layers of diffusion if you have that many different colours to even out? It would make it easy to switch between flash and LED lighting if you wanted that.

I've used large integrating rods (rectangular and cylindrical) and diffusion and even full "real" lab integrating spheres and diffusion for the camera calibration projects. Needed diffusion in all cases for this particalur application where the camera is seeing the lightsource directly. We were looking at 2-3% intensity flatness ... pretty much approximating the noise of the sensors we had/have access to.

Most of the high CRI lightsources I'm involved with use more than 3 wavelengths or phosphors to get there ... especially when you need a decent R9 value.

Regardless of the solution, you can still switch out Xenon versus LED, especially with a mixing box approach

Struan Gray
24-Oct-2012, 13:09
"shareware programs available to give you a raw spectrum from their built-in spectrometer." Do you have one in mind? Still seaching on that one. Being able to determine CRI would be handy.

There is an open source colour managment system called Argyll which will read an illuminant spectrum if the colorimeter/spectrophotometer allows it - which means it needs to be one of the higher end models. See here:

http://www.argyllcms.com/doc/illumread.html

(project home page here: http://www.argyllcms.com/)


If you don't already own one of the suitable colour calibration devices, you can homebrew a crude spectrometer fairly easily, but you can save time and effort by piggybacking off a project like this one:

http://publiclaboratory.org/tool/spectrometer


Naturally, there are more advanced options too, but for measuring a lamp's CRI or the CIE coordinates of particular LED combinations you can get by with a relatively crude instrument.

Struan Gray
24-Oct-2012, 13:13
... snip...

Thanks Rudi. Nice to know how the pros do it :-)

AGChicago
25-Oct-2012, 15:41
(Disclaimer: new forum member, first time post.) I've been developing a DSLR digital capture rig for 35mm film for 4 months or so. Ok, so a bit smaller in scale but the principles are the same and I'd like to do a 120 unit also (so XY, stitching, etc. are also an issue). I'd like to share a few things I've learned thus far, though I can't say I've found the magic bullet yet regarding lighting for all film types. I apologize for the length. I'd also like to say that this endeavor is awesome, and I believe we're only a year away from a film scanning revolution.

-As SURF states just above, the light source for positive and negative (color at least) shouldn't be the same, ideally. I started with positives, and after much researching and trials, settled on a Xenon lamp (not strobe). Xenon lamps run cooler then Halogen, have a CRI of 100, and a color temp of 3100K. I have tried multiple sources, but none produce the color rendition and saturated image of the Xenon lamp. Even close. Why? Plainly put, to me anyway, it is because a positive film exposure is already perfect. It should be lit in a neutral temp, with as high a CRI as you can muster, or you will shift the colors from what your eye sees and the film has in it. Digital positive captures using a high temp LED diffused source created a washed out image with no shadow detail. You can WB it out, and adjust color curves and saturation, but all that manipulation creates noise in the image. Shine a 5100K LED lamp at a flower, take a picture, then notice how crappy it looks. Same idea. I think the Solux Halogens will work also, as someone earlier stated, a 4700K bulb is used in some high end industrial film scanners. But I think the 4700K is a compromise between positive and negative ideal sources, and they run hot.

The setup and cal was simply to white balance on the diffusion plate with no film, capture a frame, and done. I've never had to touch the color curves or contrast. I can post a sample untouched jpg if there is interest.

-The aforementioned 3100K/100CRI Xenon bulb, when used on a color negative (I've tried various Kodaks, but no Fuji's), looks, to put it mildly, like dog doo. The orange mask is lit into a gloriously bright and highly saturated glow. When reversed, the blue channel is screaming out of control and requires significant curve adjustment. After you're done, the noise levels are through the roof and the resulting image is garbage. The first light source I bought to try was a cheap $30 76 LED "video light". With some diffusion the results with negative color are far superior. My theory so far is that it works better because the higher color temp is diminishing the saturation of the orange mask level in the capture, hence subduing the blue channel after reversal. I think similar results might be achieved using a blue 80A or 80B filter (or gel) in front of the Xenon lamp. Albeit at the expense of lumens at the frame. The idea of using some type of blue filter on the light source (or very high temp source) seems a common one when scanning or digitally capturing negative color film. The RAW file captures (pre-reversal) between the Xenon and LED are really night and day, they look completely different. I think the light source, so far, is the most challenging issue.

I plan on trying various blue filters on the Xenon tonight, just to experiment and see what I get. And negative B&W, I haven't even started with yet. I suspect that the mask colors (if the film has one) will cause issues.

Daniel Moore
25-Oct-2012, 15:55
AG, care to share some of your design details for the light source? And I'm very curious to see more of how you approached the negative stage as well, which there is a thread for here (http://www.largeformatphotography.info/forum/showthread.php?87539-DSLR-Scanner-Negative-Stages). Thanks for sharing your valuable empirical evidence.

Peter De Smidt
25-Oct-2012, 17:39
First off, Welcome to the project AG!

We've got a lot of good people working on this, and I expect that progress will increase once the snow flies.

What Xenon bulb have you been using? It's likely, as you say, that different media types will do best with unique lighting. I plan on playing with a rosco gel swatch book on my flash source.

AGChicago
25-Oct-2012, 18:52
Sure, I'll elaborate. The attached shows the prototype (sorry for handheld low rez shots). The light is a 20W undercabinet "puck" light, mounted inside of 3" thinwall PVC tube (with standard end caps). The diffuser is 1/8" opaque white cast acrylic, and the light is mounted right to it (with a 2" hole cut in the mounted end cap and front plate). You can get 35W Xenon bulbs of the same format, I'm going to try that also. In the end, a standard MR16 would be better, and the PVC will be replaced by stainless steel (with some holes to allow some air flow). When I try different lights, I just pull off the light assembly and direct the light into the mounted end cap. The opaque diffuser works fine, but more might help. Using opaque eliminates the hot spots from the light source, at the expense of light output.

A small trick I've used is to mount a 4" diameter tube to the front (PVC, but again will be stainless on the real one). This keeps any stray light from getting to the DSLR lens. The inside of the tube, and back wall in front of the film is covered in telescope flocked material. Protostar.biz sells it very cheaply, and it's pretty nice quality. So basically you're shooting into a non-reflective black hole.

Because this is for 35mm, there is the luxury in getting off the shelf film holders. I've simply created a fixed opening with UHMW polyethylene slide rails inside (it's nice and slippery and very wear resistant). I don't know if any of that is applicable to large format capture designs. Unless you fix the camera, and design a film holder that can move and index up/down between the light source and "shooting tube" front plate. Side to side is not an issue. The forum seems to be focusing on keeping the film fixed and moving the camera though.

Peter De Smidt
25-Oct-2012, 20:58
Thanks for the updates.

All of the designs I remember here keep the camera fixed and move the negative.

Amedeus
25-Oct-2012, 22:44
Hi AG,

Thanks for sharing, quite a download of information here.

One tidbit of information caught my eye ... "Xenon lamps run cooler then Halogen, have a CRI of 100, and a color temp of 3100K."

I would like to know which Xenon lamp you are referring to with a CRI of 100 and a CCT of 3100K

I also tend to agree with your observation that the light source is indeed the most challenging part as any compromise there has ramifications for the post processing.

Struan Gray
26-Oct-2012, 00:21
A quick heads up on safety: bare Xenon lamps can put out a lot of UV, enough to give you snowblindness if you are unwary during alignment or use of the capture system.

I have only worked with research grade xenon lamps (up to 1 kW - great brownouts as you start those up :-). For measurements in the visual spectrum we always filtered out the intense IR with a cold mirror, and the UV with a filter. I assume that bulbs intended for domestic use have filters integrated into the glass, but it may be that the enclosure is intended to do the filtering, in which case homebrewers will need to take UV eye saftey into consideration. The old Ilford colour gel packs for enlarging ilfochrome go for pennies on the dollar and include a useful UV filter (and a bunch of colour correction gels to boot).

AG, nice to see your setup. The rationalist in me says that you should be able to capture any piece of film with three monochromatic sources of the right wavelength. You are, after all, trying to measure the density of only three different dyes, and suitably chosen wavelengths should allow you to tease out their individual densities without cross-contamination. But, and it's a big but, both the dyes in film and the colour filters in digital cameras are explicitly designed to be used with continuous light sources, and fighting that fact leads you - as you found - into signal to noise problems.

Once upon a time there was talk of developing a film whose actual colours after development bore no relationship to the colour bands they were recording. The idea was that the freedom to manipulate the final colour would give you more freedom in chosing sensitiser dyes. Such a film might be more useful in the long term of analogue photographic capture, but I suspect the budget to develop it has long since gone.

FWIW, one advantage of an LED-based setup would be the ease with which you could take separate colour frames for RBG (or CMY), each optimised for the signal to noise of that particular channel. It would be a way of getting round the unavoidable fact that colour negs have little blue in them.

Daniel Moore
26-Oct-2012, 00:33
"FWIW, one advantage of an LED-based setup would be the ease with which you could take separate colour frames for RBG (or CMY), each optimised for the signal to noise of that particular channel. It would be a way of getting round the unavoidable fact that colour negs have little blue in them."

Struan, this begs to be expounded upon! And thanks as always for sharing your expertise.

Struan Gray
26-Oct-2012, 04:19
Daniel, the problem, as AG pointed out, is that it is very easy to get an underexposed blue channel if you do one-shot 'scans' of colour negative film with a DSLR. When you adjust the colour balance to restore the right proportions between the channels, the blue channel ends up with significantly less signal to noise than the red and green.

The problem is that colour negatives simply are not very blue if you hold them up to the light. Your eyes, and DSLR colour filter arrays, are made to sense all colours at once, and if you adjust the total gain so that you don't blow out the strongest channel, the weak one ends up underexposed.

Papers made for analogue printing from colour negatives could be adjusted so that the blue-forming layer had the right combination of sensitivity and gamma that the strong orange colour of the negative did not matter. You could make a DSLR with a higher gain for the blue pixels and achieve the same end, but nobody does that because it would be useless for taking pictures of the real world. You could make a scanner with a blue-sensitive sensor with a higher gain, but there is then the engineering problem that the sensor itself will have some optimal gain for best signal to noise, and it makes much, much more sense to keep the on-chip gains the same and have a brighter light for the blue channel.

In principle you can do this with blue-filtered incandescent or xenon light, but the spectral absorbances of the dyes in negative film are quite broad, so it is much easier to do with a narrow band LEDs whose wavelengths are chosen to minimise absorbances by the dyes they are not tuned to. The problem is usually the magenta dye, since there is no such thing as pure spectral magenta - it is a colour invented by our trichromatic vision.

Kodak and Fuji do not, as far as I know, publish the spectral absorbances of the dyes in developed negative film. They do publish the spectral sensitivities of the unexposed film, and the resulting absorbances you get from a grey exposure, which both act as reasonable surrogates to find starting points.

Struan Gray
26-Oct-2012, 05:47
Sorry, typing a bit quick to make a deadline, and missed the conclusion:

The beauty of LEDs is that you can choose three wavelengths which as much as possible avoid cross-contamination by avoiding the portions of the dye absorbance spectra which overlap. You then adjust the brightness of each type of LED (with modulation, or by adding more or less LEDs to the source) so that each channel gets as much light as it can take without being over-exposed. Post-capture you adjust the strength of the relevant channels *downwards* to balance for grey and overall gamma.

If the spectral absorbances of the dyes in the film overlap at all wavelengths, there will always be *some* cross contamination. But with better signal to noise in the blue channel you are in a better position to do something about that with further processing.

The central point is that just because colour negative film was optimised for analogue printing with an incandescent light source, it doesn't mean that will be the best light source for capture with a DSLR.

AGChicago
26-Oct-2012, 06:22
The bulbs: http://www.lightbulbsdirect.com/page/001/PROD/XenonBiPin/LVPX20BP

The CRI (go all the way to the bottom): http://www.pegasuslighting.com/xenon-light-bulbs.html

Struan- Xenon arc lamps have, from what I read, huge UV. Xenon low pressure household bulbs are incandescent. http://en.wikipedia.org/wiki/Xenon_arc_lamp .

Optimizing the three film channels individually against an LED source would be great. Can't quite wrap my head around how you would go about tuning them to a particular film.

My mistake on the XY being for the camera. I read through the posts, but after a few pages, it starts to be confusing what the question was!

Peter De Smidt
26-Oct-2012, 06:37
For color negatives, couldn't you use something like a Cree 3w red, green and blue leds, each color being adjustable, and shining all of them into a light mixing box. Now place a piece of orange film leader from the film you want to scan on the light source, and adjust the leds so that the readings through the film base for each channel are equal. For instance, in 8 bit RGB, make the reading through the film base equal to 250, 250, 250. Now the relative intensities of the three colors should remain constant for that film, although the overall luminosity might have to be adjusted some.

Peter De Smidt
26-Oct-2012, 10:52
Here's some pictures of my current light source, LS2:

http://i955.photobucket.com/albums/ae37/peterdesmidt/LS2_LED.jpg

http://i955.photobucket.com/albums/ae37/peterdesmidt/LS2_Flash.jpg

http://i955.photobucket.com/albums/ae37/peterdesmidt/LS2_Light_Souce_Entry.jpg

There are two sheets of diffusing plastic. The top sheet was removed for the flash picture. The interior is lined with white styrofoam. The bottom of the light mixing chamber is slanted towards the opening, such that the far end is as high as the opening. I use the LED for focusing and positioning and the flash for doing scans.

Kirk Gittings
26-Oct-2012, 14:07
Similar to the Beseler 4x5 color head no?

Peter De Smidt
26-Oct-2012, 14:16
Similar to the Beseler 4x5 color head no?

Probably, although I haven't seen a Beseler in 20 years.

AGChicago
28-Oct-2012, 16:36
Peter- adjusting the RGB LEDs to eliminate the mask was what I was thinking would be easier also. It's a bit iterative, but I think can be done. I've ordered some 10W RGB diodes and three PWM LED drivers (with knob adjusters). We'll see how it goes.

What are you using for your diffuser plates?

Allen

Peter De Smidt
28-Oct-2012, 16:44
Wow, 10w led's would be bright! (A lot of people are using LEDs for lighting reef aquariums. My fixtures use 3watt cree's, and you can't look at them when they're on full.) Make sure to have them properly heat-sinked.

A few years ago I bought a 4x4ft sheet of white Plexiglas. I still have some left, and that's what I use.

Peter

Daniel Moore
28-Oct-2012, 17:57
Cemil Purut, who is making custom LED enlarger lamps for sale here advised me to use 3/16" #2447 white acrylic, there are a few different translucencies available and this is the most. For the sake of thoroughness, Peter has suggested using non-glare P99 acrylic to mount the neg to.

I just mocked up a light source using the LuminousFilm panel I linked to earlier in this thread. It's an array of 49 LEDs over a total 5 ¼" square area. Placing the 3/16" acrylic 2 ½" above it resulted in very even illumination. The difference between the center and outer edges measured -4 points in photoshop, a simple matter to correct in the final stitched scan. Though I don't hold much hope for it regarding optimal color spectrum I will test that aspect shortly. The manufacturer says the panel reaches a CRI of about 80 and is between 4,000K and 5,000K. Exposure was 1/100' @f/8 ISO 100. Incidentally, this thing barely gets warm.

Peter De Smidt
28-Oct-2012, 19:11
That's a nice shutter speed. You might try using a second diffusion panel, ideally with some space between the two.

Daniel Moore
29-Oct-2012, 00:20
A second similar diffuser will help, I think it's 40% transmission so should come close to 1/30th sec. at that point, given some space and drop off. I made the world's worst spectrometer tonight and had a look at this light. It was encouraging not seeing sharp bands but rather smooth blends, similar to but not entirely like an incandescent spectrum. The blues were less smooth and seemed deficient. I plan to build another spectrometer (though really, they should have a different name, the way I build them : P) such that it can be attached to a camera, I'll put up the spectrum when I have it. The encouraging part was trying my splectromodor on other light sources at home and seeing in CFL's and other bulbs what I didn't want to see from my DSLR scanner lamp, narrow clearly defined bands surrounded by gaps. I'm very interested to see what my Epson V700 transarency lamp shows as well. Here's a link (http://publiclaboratory.org/sites/default/files/Make%20a%20Spectrometer.pdf) to the goofy job I plan to construct tomorrow.

In case it's of any interest, here's a sample of a 5"x5" area of the lamp as described at this stage.

82709In case it's not clear to any folks who haven't had the time to read everything posted previously, my present intent is to move the light source along with the negative to sidestep stitching artifacts due to less than perfect illumination or variations in illumination, repeated over individual 'scans' from a fixed light source as Peter's invaluable empirical evidence has shown can be an issue.

Struan, thanks so much for the spectrometer info!

Note to any splectromodor builders: two pieces of blue painter's tape iis very nearly .2mm, a preferred slit width for DIY jobs.

David_5527
3-Nov-2012, 15:50
It seems to me that an x-ray viewing box may be good for this...Also, the standard size if 14x17 "

Peter De Smidt
3-Nov-2012, 16:14
It seems to me that an x-ray viewing box may be good for this...Also, the standard size if 14x17 "

Are they more even than standard light boxes? My Porta-trace light box is no where near even enough.

Peter De Smidt
5-Nov-2012, 14:16
I finally had a few minutes to take some readings. I used an X-rite 811 densitometer in Status M mode, which is for color negatives. Taking a reading through the un-exposed but processed base of 35mm Fuji 100 color negative film, gave RGB numbers of R.22, G.64, and B.86. I then sandwiched Rosco gels with the negative strip and took readings to find the most equal R, G, B numbers. The winner was #70 Nile Blue. Sandwiched with the Fuji film, it gave R0.92, G1.01, B1.02.

Hopefully, I'll have some time to run some scan and see if this equalization of the RGB numbers helps.

Daniel Moore
15-Jun-2013, 15:49
Here is a copy and paste repost of the last 4 lighting related posts in the camera and positioning branch which is more pertinent here:
------------------------------
Peter J. De Smidt

Re: DSLR Scanner: Camera Supports and Positioning
We're using 60 RGB LEDs per meter ribbon:http://www.leevalley.com/en/hardware...,70322&p=70326

The controller is:http://www.leevalley.com/en/hardware...,70322&p=70327 We're using the one with three knobs.
"There are no rules here - we're trying to accomplish something." - Thomas A. Edison
www.peterdesmidt.com/blog
-----------------------------


ludvig friberg

Re: DSLR Scanner: Camera Supports and Positioning
Yes I have the same it is crazy bright! Here is the sketch I made to maximize leds per square mm. I am looking forward to seeing this in action.
------------------------------

Daniel Moore

Re: DSLR Scanner: Camera Supports and Positioning
I realize this should go into the light sources thread but I'm going with the flow here. Ludvig or anyone else, do you have any ideas on how to make (3) three digit readouts for the R,G and B values work with this RGB LED Ribbonflex strip? So far I've heard from a couple of companies I've put that question to that it'll require a DMX controller, which seems like a replacement for the knob controller we're using for starters, no harm there as long as we can input values during the testing phase, until we can establish working presets. The stock controller is analog and I wonder if there's a converter/display type doodad that can help. The only thing I've found so far is a single readout DMX controller: http://www.chromationsystems.com/sto...51r9k6c2rqjar6
I'm still working with Jeff from chromationsystems.com and will report any news.

I've also found this tidbit:

http://log.liminastudio.com/itp/phys...rgb-led-by-hue
which represents another approach but that may be too much for the circuit as it stands, pretty much out of available pins without going to an Arduino Mega or similar.
----------------------------------

ludvig friberg

Re: DSLR Scanner: Camera Supports and Positioning
Well if you want to control red green and blue with PWM from an arduino and control the light levels on r, g and b with digital control from 0-255 you could do it with three power transistors and one of these lcd shields with buttons http://www.adafruit.com/products/772. That would use up 5 pins. 2 for the display/button shield and 1 each for the R, G and B transistor. Also you could control everything else like speed on motors delays etc.

Ludvig

-----------------------------------

Daniel Moore
15-Jun-2013, 15:56
Ludvig, we haven't posted many of the project details as of yet but hope to relatively soon. We are using that LCD shield presently. It's buttons have been mapped to menu items at this stage. It's more the readout of the RGB values I'm hoping to somehow squirt into the circuit.

In the interest of progress for now, for the sake of repeatability we can simply create a decal and eyeball the knob positions.

ludvig friberg
19-Jun-2013, 15:16
I dont know how that three knob controller works but I guess that its PWM and has some transistors inside. If you wanted to you could easily drive the arduino with those pots and have arduino pulse the transistors. Then just write the values out on the lcd shield. Or perhaps just hook up the pots in parallel to three analog ins on the arduino and read the values and display them on lcd with the arduino. Last but not least you could expose some wires soldered onto the pots to the outside and read the resistance with a multimeter.

Ludvig

Amedeus
19-Jun-2013, 17:08
You need more than three LED colors "RGB" to get a CRI of over 85.

Alternatively, you can mix warm white (~3000K) with cool white (6000K) and add green and red in for balancing the spectrum out. All colors individually controlled. Split "Green" into "Cyan" and "Lime Green" for even better control. Don't forget that your "White LEDs" are blue and yellow heavy ... ;-) just the nature of the beast. CRI over 95 with good R9 is possible this way.

Since this is a fairly large area "light box", color mixing shouldn't be too much of an issue. Matter of diffuse reflection and diffusors and distance of course.

CCT and CRI will shift with temperature but camera RAW post processing in case of stitching can take care of this. Cooling the LED's is important as many times noted in this thread.

Daniel Moore
19-Jun-2013, 22:24
Some insightful ideas Ludvig, thanks! Once things are up and running and demonstrable and repeatable, oh, and viable : ) I look forward to devising the optimal method for dialing in those values.

Amedeus, I see what your saying. However, we are a bit invested (with no regard for anything but cost/convenience/and a bit of RGB separation) and I wonder if you see viability in the Ribbonflex RGB LED system for this application or not? The white temps you refer to, are they that different from being able to dial in a combination of R, G and B values? Each color is independently controlled, off to full power. I haven't taken an image of the spectrum and honestly was going to use actual RAW files to make those judgements. Peter has already done this with RGB LED and I was impressed with the tonal separation, and with only the usual amount of work, the color as well.

ludvig friberg
19-Jun-2013, 23:36
But how important is CRI? I know that drumscanners use Tungsten but the Nikon Coolscan series wich is more or less the goldstandard for 35 an mediumformat scanning ises rgb led.

Daniel Moore
19-Jun-2013, 23:58
Are digital cameras better at seeing peak R, G and B values or everywhere in between values? Are there specific wavelengths we should be targeting?

ludvig friberg
20-Jun-2013, 03:11
In my tests with negative color film I have had much better results with rgb led then with sunlight. I think that when you stimulate the r g and b photosites without any splill between them you get a much bigger gamut. the negs look supersaturated with rgb and with sunlight they are more of a mush so its easier to get balanced positives from the negs with rgb leds, they have to be desaturated after balanced though. Perhaps for positives its a different result, i have not tested that.

Peter De Smidt
20-Jun-2013, 06:18
The pro flat beds, such as a Cezanne, use 1990s florescent bulbs. I doubt their CRI is very high.

ludvig friberg
21-Jun-2013, 04:37
This response curve is for ektar. Not exactly a good "cri" or blackbody response. In my experiments I have chosen leds with a similar wavelength to the peaks in colornegatives and my sensor.
97379
Coincidently sensors are quite similar in their response curve.
97380

Amedeus
24-Jun-2013, 16:34
Some insightful ideas Ludvig, thanks! Once things are up and running and demonstrable and repeatable, oh, and viable : ) I look forward to devising the optimal method for dialing in those values.

Amedeus, I see what your saying. However, we are a bit invested (with no regard for anything but cost/convenience/and a bit of RGB separation) and I wonder if you see viability in the Ribbonflex RGB LED system for this application or not? The white temps you refer to, are they that different from being able to dial in a combination of R, G and B values? Each color is independently controlled, off to full power. I haven't taken an image of the spectrum and honestly was going to use actual RAW files to make those judgements. Peter has already done this with RGB LED and I was impressed with the tonal separation, and with only the usual amount of work, the color as well.

I fully understand the desire to keep it simple RGB. Makes life easier in light of the use and the need to be able to generate pure R, G and B separately, this is, within the limitations of the choosen LEDs. Saturation is great though and as Ludvig mentioned, desaturation is often needed to restore a sense of natural.

I'm not familiar with the Ribbonflex RGB LED system but will look into it.

The white temps I'm talking about are being dialed in changing power to up to 7 LED channels. Not that different than RGB but with a more accurate "broadband" spectrum. The spectrum of LEDs is "spiky/peaky" with a limited bandwidth. The Bayer filter combination in an imager (or RGB filter solution with 3 imagers) have a broader spectrum with more accurate coverage than what the LED is able to produce. RGB LED's combined also have a different response curve than what the eye perceives.

You can't record what's not there ... you can fool the eye briefly in sequential viewing, not in side-by-side. The results may be different for negatives than for positives. I'm mostly dealing with "positives" in my work.

As for Color temperature CT is only valid for black body curves ... we talk about CCT for everything else. Two different animals. 3000K CT from a true black-body radiator is unlike the 3000K CCT from a LED RGB source or CFL.

Hence the need for CRI and when that was no longer sufficient ... planckian locus, McAdams ellipses for more accurate definitions.

Amedeus
24-Jun-2013, 16:36
Are digital cameras better at seeing peak R, G and B values or everywhere in between values? Are there specific wavelengths we should be targeting?

Digital camera's see also "in-between" the RGB LED peaks.

ludvig friberg
25-Jun-2013, 03:36
Rudi, thanks so much for helping us out on this! I am a complete amateur and I dont understand the scientific words you mention but I understand "7 led". At least i think so. Could you descibe a bit more in depth how one could put together something like that? I have mostly been doing research into negatives but reversal medium is also very important. I have done some tests with combining r,g,b leds with warmwhite an coldwhite leds to fill in the gaps. It is kind of tricky to dial it in becouse I dint know the spectrum of the white leds. I guess a spectrometer would help? Is there cheap ones of any use to us you think?

Daniel Moore
6-Jul-2013, 16:48
Here's the best image I could obtain of the spectrum for the Armacost RGB LED strip lights were using:

98296

This is taken with a one of these spectroscopes:
http://www.ebay.com/itm/Diffraction-Spectroscope-Gemological-Gem-Shipfrom-USA-/320404890537?pt=LH_DefaultDomain_0&hash=item4a999ea3a9

strapped to a Logitech C525 webcam.

Daniel Moore
28-Jul-2013, 23:37
So starting to see a couple results from this Armacost RGB LED light source and firstly I'll say that I've haven't ever had such an easy time arriving at pleasing color from color negative scans. Peter made an early test and found dialing in a neutral value on an image containing a good grey target makes a huge difference in the correctibility of color and that neutralizing using the film base didn't. A benefit of using this controller is the ability to establish the optimal grey balance and color range consequently. Based on his advice I dialed in a nearly neutralized aged wood in Skyler's chair. Even with many years of ownership of an Epson V700, dissatisfied, I eventually tossed every scan in the garbage. These scans take seconds to tweak to a good starting point.
Thank's Peter for your perspicacity.

Edit: I should mention this is a 9 image 500MB 8 bit stitch of a 6x7cm color neg with stitch control point errors of less than a single pixel.

This is a good time to be careful with posting results but it's looking promising.

99449

jb7
29-Jul-2013, 02:41
Looks great Daniel-

I've gone back over a few pages, but these scanner threads are split up into so many sections now it's difficult to get a grip on a single machine. Now that you're putting such nice stitches together, might it be time to show your scanner in a single thread? Just wondering...

ludvig friberg
29-Jul-2013, 04:48
This looks very good!
I have some questions for you if thats alright?

How long time do you estimate a scan takes? With mounting, taking the pictures and postprocessing(stitching)?

Do you happen to have access to another scanner, like a Nikon or your V700? Would be very interesting to see the difference in color and dynamic range also resolution. I guess this will beat the v700 at resolution.

Did you use Vuescan or similar for negative to positive or did you do it in Pshop?

Peter De Smidt
29-Jul-2013, 06:42
We do have access to other scanners, and down the road we'll do comparison scans. Right now, though, I'm working on getting my scanner operational. The new light source is bigger than I originally planned with a 6x8" light source size, and this requires making some adjustments to the system. After that is done, we have lens testing and other types of refinements to do before it makes sense to do some comparisons.

I invert my images in a RAW processor. I think Daniel uses Capture 1, but he'll have to verify that. You guys should talk him into showing a video of his prototype in action. It's a very elegant and compact design. Of course it shows the typical prototype battle scars.

Daniel Moore
29-Jul-2013, 17:11
I will create a video of it in action once I complete my most recent modifications, new motors and upgraded belt clamp. I took a wild leap and attempted to make an X/Y stage from two stacked IGUS Drylin rails. They are anything but precise in their build, in fact they are sloppy, but seem to be precise enough in the resulting travel. Peter is using rails and bearings that are capable of far greater precision. Still a lot of tests to perform as he mentioned. I no longer own the V700, I feel a curse has been lifted being free of it. I know lots of folks are happy with it though.

I am using Capture One at this stage, tethered to a D800E. I find it's sharpening to be excellent, the main reason for using it right now.

I'm wet mounting with lighter fluid for now (I have plenty of less than stellar film exposures to test with : ). I lay a spacer on the glass, squirt the glass, lay the film against the spacer which aligns the film edge and centers it at the same time, no taping, squirt the film, lay a sheet of mylar down. That takes a minute or so. A 9 shot 6x7cm scan takes about 45 seconds give or take with delays programmed for settling the carriage motion and another for a 2 second exposure delay mode. For the image I posted I inverted in C1 with the levels slider and then adjusted the color by pulling the white and black points for each of the three channels until they touch the histogram curve. That's all for the Raw files, which takes maybe 30 seconds. Processing for these Raw files takes less than a minute on a new build with a 500MB/s SSD and i7-4770 CPU. Stitching the Tif output in PTGui using Sinc36 takes another minute. Using Sinc256 takes a few minutes. No intervention has been required as of yet to get a good stitch but that's undoubtedly coming up with featureless areas.

I'll post details of the build in a few days, still ironing out some things. I will say that wet mounting makes the impossible possible. All of the tests I've done so far are on a roll of film that was in a tube for a year and has a terrible curl which was easily tamed by wet mounting. DOF is so incredibly shallow that it may even be mandatory.

Resolution with this camera at 1:1 is a little more than twice the V700 if one takes the widely accepted V700 2100 spi as a given. 7cm turns into 47.5" @ 300 dpi with this camera.

I'm eagerly waiting for comparisons myself! Drop me an email if you'd like to arrange for me to scan a sheet of your film, this seems a good way to get a range of comparisons. All I know at this point is I'm over the moon with my color neg scans for the first time ever, and I'm amazed at how easily they were obtained. All those hours I spent with different programs tweaking tweaking tweaking. God.

Daniel Moore
29-Jul-2013, 17:21
For your edification, here's the spectrum from the V700 bulb:

99494

Peter De Smidt
29-Jul-2013, 17:33
A friend of mine has a V700 that we can use to do comparison scans.

Ignoring film flatness for the moment, how do the wet-mount versus dry-mount scans compare quality wise?

Daniel Moore
29-Jul-2013, 17:36
I'll give that a proper look and post results. My machine is in many small pieces at the moment.

Daniel Moore
31-Jul-2013, 21:30
Here's some results from a dry vs. wet mount of a Provia 400X slide. First, this is entirely unprocessed output from Capture One. I adjusted the light source RG and B values until I saw a desired white in the lighthouse, just slightly warm for the time of day, late afternoon. All other settings were at default. No additional sharpening, which I normally do. I'm masking the area outside the image and using a lens hood for both.

99562

I routinely used a polarizer with the Mamiya 43mm, I routinely regretted it as well. A grad filter would have been a much better choice here. Like I said earlier, I have lots of bad images to test with, but I digress.

Dry mounted I can see a slight curl in the film even though this was stored flat and seemed so until light grazed the surface. In the 100% crop below it doesn't show very much but in the center areas of the film the sharpness is noticeably affected. Another difference is the color of the sky, lighter, more washed out in the dry mounted test. The grass seems more harsh to me dry mounted, the wet being of subtle but noticeably better tonality.

As for dust, I have much more in my wet mount and I believe that's due to contaminates in the lighter fluid I'm using, and that 'm reusing a sheet of mylar so no conclusion should be drawn regarding dust. Likewise scratches, this is not the test for that and I need to obtain some respectable wet mounting fluid before I get any more scientific.

It does seem to me unless the magnification ratio (1:1 here) were reduced to increase DOF that wet mounting will produce a sharper scan by virtue of film flatness alone.

99563

In this image I had one orphaned image (top left) and I used dust and film edge, picking only 3 control points manually to tame it well. Control point errors were an absurdly low .1 pixel.

Color accuracy is extremely good here comparing the output to the original slide. The blues are spot on and the grass a dying green. I don't like the image but I do like the scanner's output very much as with color neg. The amount of work to get there for this image was zero once the light source was neutralized. How this will apply to different rolls of film I have yet to find out but it takes perhaps three or four test shots at the most to nail a starting point.

Peter De Smidt
31-Jul-2013, 23:02
Nice test!

Daniel Moore
31-Jul-2013, 23:16
A lighthouse seemed only fitting : ).

It seems to me that the dry mount makes the grain slightly more apparent as well. None of these are deal killers for dry mounting though I seem to recall from one of your tests that it made a more pronounced difference in black and white tonality. I'll try and corroborate that as well. This 1:1 stuff is really murder on my often less than disciplined shooting technique! The up side is I'm getting used to embarrassing myself. Wet mounting is new to me and these may be points that have been done to death, but the wet mount/DSLR capture method is somewhat new so bear with us.

ludvig friberg
1-Aug-2013, 01:10
Very interesting.
Thanks for posting this, it is very encouraging to see you getting so good results.

Keep up the good work

Ludvig

Daniel Moore
1-Aug-2013, 01:28
Thank you Ludvig, that's much appreciated. To go out on a limb as long as this, waiting many months to even know if it's viable, well, it's good to be able to say it looks worth the effort.

I've spent the entire day scanning with the machine, it's a bit addictive. I'm finally seeing so many of my images the way they I hoped they would look, without needing various software packages with lots of settings and hours of effort. Maybe one day I'll even post a really good image, I must have one somewhere.

I have had many images printed by ye olde high quality service bureaus and know what an image should look like, thus my frustration with the V700 (I have to stop bashing that thing, perhaps I'll just burn it's effigy and be done with it).

Ironic to be shooting good images of film digitally. My camera will probably see more action in here than out there.

Peter De Smidt
19-Aug-2013, 19:01
Almost there...

Peter De Smidt
20-Aug-2013, 20:38
I just placed a BW negative on the light source. With the camera at Lo 1, F5.6 on the Micro Nikkor at 1:1, and the lights up full, an exposure at 1/60th of a second seemed about right.

marfa boomboom tx
3-Sep-2013, 08:45
to the two recent designers:

what prompted the 'traveling light box' implementation?
It appears that Peter and Daniel attach the film to a "light box" and move this assembly beneath the camera.


just wondering if you had tried any other method before taking this common approach

Peter De Smidt
3-Sep-2013, 11:13
Sure, my first version, the one that required manual movement, had a fixed light source. The main advantage of a fixed light source is that it can be smaller. The downside is that any unevenness is repeated with each capture. Could that be overcome? Sure.

marfa boomboom tx
3-Sep-2013, 13:16
thanks...

nonuniform
5-Sep-2013, 14:06
I would love to see some more photos, especially of your film mount system for wet mounting. I don't really get the spacer concept. On my v750 wet mount, I just squirt the glass, lay down the film, add mylar. No taping for that. I was thinking I would go with a similar setup for my own scanner, so, I'm wondering how the spacer helps, or, well, whatever!

Thanks!
Andrew


I will create a video of it in action once I complete my most recent modifications, new motors and upgraded belt clamp. I took a wild leap and attempted to make an X/Y stage from two stacked IGUS Drylin rails. They are anything but precise in their build, in fact they are sloppy, but seem to be precise enough in the resulting travel. Peter is using rails and bearings that are capable of far greater precision. Still a lot of tests to perform as he mentioned. I no longer own the V700, I feel a curse has been lifted being free of it. I know lots of folks are happy with it though.

I am using Capture One at this stage, tethered to a D800E. I find it's sharpening to be excellent, the main reason for using it right now.

I'm wet mounting with lighter fluid for now (I have plenty of less than stellar film exposures to test with : ). I lay a spacer on the glass, squirt the glass, lay the film against the spacer which aligns the film edge and centers it at the same time, no taping, squirt the film, lay a sheet of mylar down. That takes a minute or so. A 9 shot 6x7cm scan takes about 45 seconds give or take with delays programmed for settling the carriage motion and another for a 2 second exposure delay mode. For the image I posted I inverted in C1 with the levels slider and then adjusted the color by pulling the white and black points for each of the three channels until they touch the histogram curve. That's all for the Raw files, which takes maybe 30 seconds. Processing for these Raw files takes less than a minute on a new build with a 500MB/s SSD and i7-4770 CPU. Stitching the Tif output in PTGui using Sinc36 takes another minute. Using Sinc256 takes a few minutes. No intervention has been required as of yet to get a good stitch but that's undoubtedly coming up with featureless areas.

I'll post details of the build in a few days, still ironing out some things. I will say that wet mounting makes the impossible possible. All of the tests I've done so far are on a roll of film that was in a tube for a year and has a terrible curl which was easily tamed by wet mounting. DOF is so incredibly shallow that it may even be mandatory.

Resolution with this camera at 1:1 is a little more than twice the V700 if one takes the widely accepted V700 2100 spi as a given. 7cm turns into 47.5" @ 300 dpi with this camera.

I'm eagerly waiting for comparisons myself! Drop me an email if you'd like to arrange for me to scan a sheet of your film, this seems a good way to get a range of comparisons. All I know at this point is I'm over the moon with my color neg scans for the first time ever, and I'm amazed at how easily they were obtained. All those hours I spent with different programs tweaking tweaking tweaking. God.

Peter De Smidt
5-Sep-2013, 14:12
Daniel only uses the spacer to keep the negative lined-up properly. We want to avoid having to do any image rotation in post production, as that leads to a loss of quality.

Daniel Moore
5-Sep-2013, 15:40
Exactly. I've found that with care, it's not hard to prevent bubbles being formed. When they are you need to be extra careful to push them out keeping a couple fingers on the mylar to prevent slipping around once the spacer is removed. I'm remaking the spacers to allow for more accurate indexing along both axes, an L shaped spacer. I'll be posting more detail images soon.

DannL
5-Sep-2013, 19:53
101442 101443 101444 101445

A simple, inexpensive, portable, bright, uniformly lit, cold-cathode light source for countless projects. I've been using these off and on for a number of years. They work great as a small light-table for viewing negatives up to half-plate size (4.75"x6.5").

HP made a scanner that came with this ScanJet XPA Transparency Adapter. This particular XPA (pictured) was purchased off eBay several weeks ago for $5.00 minus shipping.

To adapted the XPA to work without the scanner . . . You will need a DC power source. I used a 12 volt DC, 4 amp power supply from an old Sony video camera. Cut the connector from the end of the XPA's cable. Attach the power source to the red wire = (+12 VDC) and black wire = (ground). Seal those connections with electrical tape. Twist the orange and brown wires together to make a separate connection and seal with electrical tape. Seal all your connections with electrical tape.

I've been using mine with a 12 Volt DC power source. So far, so good. But, if anyone knows a different voltage requirement for this unit, please let us know.

Measurements: XPA case is 8-3/8" L x 7" W x 1-3/4" H. The screen is approx. 5-1/2" x 6-1/2".

Enjoy!

PS: If you decide to invest in one of these, my recommendation is . . . "The Newer, the Better". The screen can get scratched up if handled roughly.

Peter De Smidt
5-Sep-2013, 20:07
That an interesting light source. Thanks for posting!

Daniel Moore
6-Sep-2013, 01:20
Nice catch.

DannL
6-Sep-2013, 06:38
101449 101450

The last picture in my previous post doesn't do a good job of depicting the screen brightness. This is probably a better representation. Internally there are fluorescent type tubes around the edges. They require a minute to warm up to reach full brightness.

Peter De Smidt
6-Sep-2013, 16:43
I'll pick up one of DannL's light sources when I get the chance.
It'll be interesting to see how it's spectrum does with colors.

I really like the ability of our current light source to adjust the RGB composition of the light. I've scanned a few bw negatives developed in a staining developer (Pyrocat). Being able to roughly equalize the capture of the three channels is useful.

Daniel Moore
6-Sep-2013, 22:41
Here's another example from this light source. It was shot with an Arca Swiss F Classic and Schneider 58mm lens. I dialed in a nearly neutral film base with the RGB controller and got it closer in Capture One. Besides inverting the black and white points, correcting the black point was the ONLY editing done to this image:

https://www.dropbox.com/s/y5qakswy1hq49mo/Hunter%20patio%20sm.jpg

Here's a 100% crop from the best focus point in that image with only default sharpening:

https://www.dropbox.com/s/dfvmq7tf93takeh/Hunter%20patio%20100%25%20%20crop.jpg

The result file as captured with my D800E is 80" long at 300 dpi. using almost exactly 1:1 magnification.

Color me happy.

I deleted the previous post as the images were being resized too small. I'll make a note to leave them in my dropbox.

jb7
7-Sep-2013, 07:04
You're both getting great work done on this, very impressive. Very nice scan Daniel...

Peter, I'm glad you mentioned that the unevenness problem of a smaller fixed light source might be overcome; if I ever get back to this, I'll be continuing to develop that approach. I have a strategy for dealing with it, but I've been preoccupied with other projects recently.

Daniel, I'm glad you mentioned the timing of the process- my own experiments pointed towards faster scanning and processing times for large originals than is possible with a V750, and your mention of double the resolution sounds about right. I might not comment to every post, but I'm following it all with great interest still, and there might come a time when I have to ask some questions about wiring and sketches...

Thanks for keeping us updated...

Daniel Moore
7-Sep-2013, 14:29
Here's an edited version of that file to correct the cyan cast, took all of one minute in PS:

https://www.dropbox.com/s/v8lwxhv16m7u77c/hunter%20patio%20edited.jpeg

Daniel Moore
15-Sep-2013, 19:50
Here's the result of a test for a couple of different potential problems. It's a product of stitching a 4x5 array of the light source itself. There are no control points to be found obviously so I used a template and replaced the detailed images with this set. This has proven to be very successful. You can see here the 4x5 mask around the edges which shows a stair stepping effect between shots. It indicates the mask is not positioned identically to that of when the template set of images were made. This drives home the point that template work must be perfectly aligned to work. I use an edge guide when laying down the film which keeps the long edge lined up the same each time. Shifting laterally will make no difference in practice, rotation will ruin template work. The test was designed to reveal unevenness in blending between shots as well as the falloff of the light source itself. There is falloff and I'll use this result to create a mask to reverse it. There is no evidence of blending artifacts. The fastest way to bring those out is to reduce the image on screen to the size of a postage stamp. At that magnification readily visible grid lines begin to show, outlining each of the separate shots. Here I'm using PTGui and it's built in blending algorithm.

101871

Here's an image generated by using another images control points and simply hitting PTGui's 'Create Panorama' button. No new control points, no re-optimization, simply swapping out all the images from a different and nearly perfectly optimized fully detailed film scan. At 100% there are zero visible defects in the replacement stitch. Stitching featureless areas that have been problematic in the past should be no problem at all with a careful templating approach.

101876

Peter De Smidt
15-Sep-2013, 20:09
That's good news, as long as my rig is repeatable enough for template work. I dislike manually adjusting control points.

How do you plan on using the image of the light source to reduce irregularities? Duplicate the layer. Invert it. Lower opacity until there's no variation in tone?

Daniel Moore
15-Sep-2013, 20:15
I don't know yet : ).

I was thinking it might work to shoot a new set where the brightest area in the center is at or near 128 value, convert it to black and white and invert it and put that layer in overlay mode. Open to ideas though.

edit: just tested that with a quick gradient mask and it does seem to work ok at first glance. I'm still using a white walled interior. Once I line it with Aluminum HVAC tape I'll test again. Even as it is, it's hardly a bother.

Daniel Moore
15-Sep-2013, 21:22
I imagine things will drift after a while. It's probably best to plan for those featureless stitches by creating a new template every so often, or for super critical work, right before. As long as no rotation takes place give or take a pixel, should work fine. I'd also like to point out that if the film edge and the straightness of travel relative to the camera sensor are not perfect, the template will have calculated this into it's control point solution and that should become irrelevant. I know my setup isn't calibrated to that degree.

jb7
16-Sep-2013, 02:30
Very good- I doubt whether my own strategy for positioning would be as capable of such precision for making subsequent scans-
though I plan on making large overlaps...

Daniel Moore
18-Sep-2013, 23:25
For the purpose of control point generation overlaps of as little as 15% typically suffice. It's only those sky areas and other nebulous/featureless zones that pose a problem without a repeatable template. I hope you'll share with us your progress and as you go, Joseph. Perhaps we can kibbutz a bit : ).

shijan
28-Jan-2014, 05:22
take a look at this new hi CRI LEDs http://www.yujiintl.com/high-cri-led-lighting

Daniel Moore
28-Jan-2014, 09:12
Thanks, Shijan, this is very interesting and worth looking into.

Daniel Moore
29-Mar-2014, 10:00
Quote from rbultman in the scans and comparisons thread: "I'm having a hard time visualizing how turning on each color for a specific duration works relative to PWM? Did you try different PWM frequencies? What about using a low-pass filter after the PWM output to reduce ripple or using a DAC output? How many effective bits do you need to acheive the color range? Are you using a custom LED setup of your own design or a commercial one? Are you just looking for a change in color temperture of the light source?"

We're using an Armacost Color Controller from Lee Valley. The frequency is hard coded and I'm not familiar enough with it's inner workings to try and change it. The workaround is to turn the LED's on and leave them on during exposure rather than pulsing them on and off with PWM, which caused the banding artifact. Need more blue?, leave it on longer than the others for example. I read a low pass filter could help but this solution seemed easier. The color temperature is not the real goal of having the ability to adjust the LED's, it more to dial in a neutral gray before capture for each film scan to optimize color and tonal separation relative to the putput in one's preferred Raw processing program. This made obtain pleasing color straight forward and well worth the minute or so it might take to find it through trial and error. Using the same values for different exposures of the same film made it even faster as they provide very good starting points.

rbultman
29-Mar-2014, 11:17
Thanks for moving this here. I now realize that there are dedicated threads and will try to keep to the subjects of each.

Is it this (http://www.homedepot.com/p/Armacost-Lighting-RGB-LED-Color-Controller-with-Handheld-Remote-for-21-Colors-with-Color-Changing-Effects-AL-RGB4A-12V/203227255) one?

Daniel Moore
29-Mar-2014, 11:56
The one we're presently using is not programmable. http://www.leevalley.com/en/wood/page.aspx?p=70327&cat=1,43349,70322
That's going to go away however and be replaced by mosfets as in this circuit which does not rely on PWM and has only Red and Blue controls as the Green channel was always used the most for all film types:

https://copy.com/AWBinZu4cPdUKorC

Scanduino V2 will also use a different display, an OLED similar to what ReallySmall is using for his Stackduino V2, but that's a way off. Most of this circuit is a derivative of Stackduino (https://www.flickr.com/photos/reallysmall/12755494825/). The drive towards generating an actual PCB is likewise driven : ).

marfa boomboom tx
30-Mar-2014, 12:53
other options, not as high tec, could be:

hasselblad: http://www.bhphotovideo.com/c/product/276379-REG/Hasselblad_10700022_CCD_Drum_Lamp.html

aztek: http://store.aztek.com/servlet/-strse-217/Drum-Scanner-Lamp-Drum/Detail


best,
rl

rbultman
31-Mar-2014, 03:04
Very cool stuff Daniel. Fritzing looks very cool. I've never used it. I'm looking forward to your progress on this.

Regards,
Rob

Daniel Moore
2-Apr-2014, 20:17
Rob, that circuit is fully functional, the code needs an update to support the mosfets though. I'm going to keep at the PCB version and if successful, supply the boards for DIY'ers to solder up, or perhaps offer completed boards if someone wanted one.

A pickard
17-Jun-2014, 11:50
I am just getting started using a DSLR scanner with a copy stand and a D800 with a 105mm f/2.8 macro lens. For my light source I am using an Artograph Lightpad http://www.artograph.com/lightboxes/lightpad-930/ I am using this for B & W MF & LF B&W negs and it seems to be appropriate. Not sure about color temp & response. Since its not as bright as a flash unit, I lock the mirror up and use CaptureOne tethered to trip the shutter to reduce vibration. The light source seems even and I move the neg rather than the light source. At some point I hope to make an X-Y stage to move the neg carrier around. Thanks to all for your great input and suggestions.

Peter De Smidt
17-Jun-2014, 12:13
Thank you for posting. One of the great things about this is that it can be as complicated or simple as you wish. Tethered capture is a good idea. Please keep us updated on your progress.

Zndrson
20-Jun-2014, 05:24
Hi all,

Though I have not read through every post in this thread, I did want to offer my solution for correcting evenness issues using a light box/other light source.

In Capture One, there is a little known tool used mostly by Technical Camera photographers with digital backs called the Lens Cast Correction tool (LCC).

Used properly, a calibrated piece of translucent plexiglass is placed directly in front of the lens of the Technical Camera. An exposure is taken for middle grey, or slightly under.

http://www.directdigitalimaging.co.uk/media/c1c/ulclargeformat.jpg
https://www.onlandscape.co.uk/wp-content/uploads/2012/07/print-sharpening_0008_f_8.jpg

The resulting image shows all of the lenses faults (vignetting, color cast, etc.). When an LCC is created in Capture One and applied to that same image, the software corrects for all of the faults. Those adjustments can then be applied directly to images taken using that camera/digital back combination so that the image is correct from the beginning.

I use this same technique when scanning with my D800, though the piece of plexi is replaced with the light table. I take an image of the light table first, and create an LCC in Capture One from that image. Then I'll photograph the negative, and apply that LCC to the image of the negative.

The benefits are obvious, and provides me with piece of mind. The software works very well, especially with subtle gradation changes. It can't work magic and make black to medium grey without significant noise, but as long as you get pretty close, the LCC application will do the rest of the work for you.

Hope this helps someone. Sorry of everyone knows about this tool already and is already implementing it in their workflow!

Daniel Moore
14-Oct-2014, 21:18
A late reply (sorry, I was doing summer : )).

This is an excellent corrective technique for those setups employing a fixed light source as in Peter DeSmidt's first incarnation, a flash based unit.

I have to wonder what the real world difference would be now that both Peter and I (and anyone else out there) have moving, full film size light boxes, would this be enough to rule out the falloff in a result stitch? I'm not in a position to test that theory easily.

This could really make someone's day, depending on their approach.

Peter De Smidt
14-Oct-2014, 21:36
Yeah, that's a great idea for use with a fixed light source.

madumi
10-Feb-2015, 20:58
Here's the results of the experimentation I went through to obtain an evenly illuminated light source... I'll break it into separate posts as there's a limit of 4 pics per post...


Attempt #1 - styrofoam box with a 45 degree reflecting bend

129115

I took the time to adjust the angle of the reflecting bend so that the intensity of the reflected light beam aimed for the center of the final opaque light source. Having said that, the results were the worst for edge darkness. I tried lining the outside of the styrofoam box with aluminum foil, which didn't seem to help. I also tried using diffuse light before it entered the box (which made no difference).

Please excuse the drill holes in the opaque acrylic. It was the only piece i had on hand at the time (overlapping the internal dimensions of the box). Here's an unedited capture of the light source:

Dimensions of the internal styrofoam tube are 18cm x 12cm
129116

And Here's the same light source with the levels crushed to within 10 RGB values:

129117

madumi
10-Feb-2015, 21:04
Attempt #2 - mirror box with prismatic acrylic sheets

I put together a box using 98% reflectivity aluminum. My thought was that the internal reflections would create a perceptually wider light source. Here's the box:

129119

Here's the view inside the box:

129120

This attempt was probably about equally unsuccessful... Try as I did, I could not eliminate a distinctive hot spot in the middle of the acrylic. I tried an additional layer of prismatic acrylic in the middle of the tube, but it had little discernible benefit. For what it's worth also, the 98% reflectivity aluminum also seems to reflect colors better from the red end of the spectrum, so there's a slight tinge to the color spectrum.

Here's an unedited capture of the resultant light source.
Dimensions are 18cm x 12cm

129121

And here's the same capture with the levels crushed to within 10 RGB values

129122

madumi
10-Feb-2015, 21:15
Attempt #3 - Acrylic sheet set over a masked beauty dish

This seems to hit a sweet spot.
Here's a pic of the masked beauty dish. The mask has a diameter of 21.5cm & the beauty dish is 70cm dia.

129123

Here's a side view of the setup:

129124

By varying the distance between the masked beauty dish and the acrylic, the shadow it casts can be increased (by reducing the distance), or decreased (by increasing the distance).

Here's a pic of an unedited capture of the light source
Dimensions are 30cm x 30cm

129125

And here's the same capture with the levels brought to within 10 RGB values:

129126

This was definitely the most satisfactory setup. If you blur the unedited capture (there should be some bokeh involved in DSL capture anyway), the RGB values are within 1 of 255 values -- very acceptable, and it would not be hard to tweak the setup (I did not bother as I figured I would do that with the final design).

The edge darkness in the acrylic is due entirely to the sides receiving no light cast on it. This could be fixed with bevelling the acrylic or maybe introducing a white reflector to surround the setup. I feel confident that the unevenness in the light source could virtually be eliminated, possible with a larger mask on the beauty dish, possibly with an opaque mask or by playing with the distance--there's many options for tweaking

madumi
10-Feb-2015, 21:23
Last of all, mainly to satisfy my curiosity, I tried narrowing the diameter of the beauty dish by cutting a mask for the outside (32cm diameter) like this:

129127

Then I re-ran the tests I had done with the larger diameter beauty dish... The result was that overall evenness of the illumination suffered. I tried several times, but the overall setup proved much more finicky, and definitely not worth the time...

Tin Can
10-Feb-2015, 21:33
Last of all, mainly to satisfy my curiosity, I tried narrowing the diameter of the beauty dish by cutting a mask for the outside like this:

129127

Then I re-ran the tests I had done with the larger diameter beauty dish... The result was that overall evenness of the illumination suffered. I tried several times, but the overall setup proved much more finicky, and definitely not worth the time...

Thanks for showing your results. Good work.

The 90 degree styro box has never made sense to me, it must have been driven by marketing people who demanded heads for low ceilings.

All very interesting!

Tin Can
10-Feb-2015, 21:37
Hi all,

Though I have not read through every post in this thread, I did want to offer my solution for correcting evenness issues using a light box/other light source.

In Capture One, there is a little known tool used mostly by Technical Camera photographers with digital backs called the Lens Cast Correction tool (LCC).

Used properly, a calibrated piece of translucent plexiglass is placed directly in front of the lens of the Technical Camera. An exposure is taken for middle grey, or slightly under.

http://www.directdigitalimaging.co.uk/media/c1c/ulclargeformat.jpg
https://www.onlandscape.co.uk/wp-content/uploads/2012/07/print-sharpening_0008_f_8.jpg

The resulting image shows all of the lenses faults (vignetting, color cast, etc.). When an LCC is created in Capture One and applied to that same image, the software corrects for all of the faults. Those adjustments can then be applied directly to images taken using that camera/digital back combination so that the image is correct from the beginning.

I use this same technique when scanning with my D800, though the piece of plexi is replaced with the light table. I take an image of the light table first, and create an LCC in Capture One from that image. Then I'll photograph the negative, and apply that LCC to the image of the negative.

The benefits are obvious, and provides me with piece of mind. The software works very well, especially with subtle gradation changes. It can't work magic and make black to medium grey without significant noise, but as long as you get pretty close, the LCC application will do the rest of the work for you.

Hope this helps someone. Sorry of everyone knows about this tool already and is already implementing it in their workflow!

Great info. I wonder if there is way to do this with PS. I also wonder if a 'dust off' Nikon shot would work. I am not that handy with these procedures. Nor do I want to buy Capture 1. I spent enough with Adobe CC and my D750.

And no, I don't think all of us know much about this.

Thanks for sharing!

Daniel Moore
10-Feb-2015, 21:53
Good stuff, Bert. Thanks for sharing your results.

My suggestion, and it's admittedly a shot in the dark, would be to get the best uniformity you can and lock it down. Then make an image of the light source at the intended brightness and invert it, then print that on transparency meant for overhead projectors, and secure it to the diffuser. With some trial and error that could effectively negate any residual unevenness.

Are you designing this to be a non stitching platform? Single capture of larger formats? Please let us know what your approach is.

ludvig friberg
11-Feb-2015, 03:50
Hi There!

I always had the best result from building a integrating sphere with leds as lightsource. What you need is a sphere with a diffuse interior. The hole should only be 5-10% of the surface area so you need quite a big one for 1:1 . The smaller tiles obviously needs a smaller backlight if the light is static with the camera and the neg moving and so the sphere can be smaller. I have used several 1-3 watt leds and it works very nice. Its best to flash them only during exposure I find since that means I can get away with smaller heatsinks. Here is a picture of a commercial one http://goo.gl/lS2wdI . Its easy to build, you need to find a sphere at the right size and right material, then split it in two and paint it with the mattest whitest paint you can find. Make a hole for the camera and a hole or several for the light(s). Then put it back together. If you find one with a nice white matte interior that works well you can of course skip the splitting with is nice.

http://s12.photobucket.com/user/barrymilton/media/sphere6.jpg.html
http://s12.photobucket.com/user/barrymilton/media/sphere1.jpg.html

Michael Cienfuegos
11-Feb-2015, 16:02
Hi all,

Though I have not read through every post in this thread, I did want to offer my solution for correcting evenness issues using a light box/other light source.

In Capture One, there is a little known tool used mostly by Technical Camera photographers with digital backs called the Lens Cast Correction tool (LCC).

Used properly, a calibrated piece of translucent plexiglass is placed directly in front of the lens of the Technical Camera. An exposure is taken for middle grey, or slightly under.

http://www.directdigitalimaging.co.uk/media/c1c/ulclargeformat.jpg
https://www.onlandscape.co.uk/wp-content/uploads/2012/07/print-sharpening_0008_f_8.jpg

The resulting image shows all of the lenses faults (vignetting, color cast, etc.). When an LCC is created in Capture One and applied to that same image, the software corrects for all of the faults. Those adjustments can then be applied directly to images taken using that camera/digital back combination so that the image is correct from the beginning.

I use this same technique when scanning with my D800, though the piece of plexi is replaced with the light table. I take an image of the light table first, and create an LCC in Capture One from that image. Then I'll photograph the negative, and apply that LCC to the image of the negative.

The benefits are obvious, and provides me with piece of mind. The software works very well, especially with subtle gradation changes. It can't work magic and make black to medium grey without significant noise, but as long as you get pretty close, the LCC application will do the rest of the work for you.

Hope this helps someone. Sorry of everyone knows about this tool already and is already implementing it in their workflow!


Great info. I wonder if there is way to do this with PS. I also wonder if a 'dust off' Nikon shot would work. I am not that handy with these procedures. Nor do I want to buy Capture 1. I spent enough with Adobe CC and my D750.

And no, I don't think all of us know much about this.

Thanks for sharing!

I found that I could use the clean lid from a Starbucks coffee cup and it worked well.

m

Tin Can
11-Feb-2015, 16:52
In video editing there is LUT.

http://www.youtube.com/watch?v=onom8tpiof8

Peter De Smidt
11-Feb-2015, 18:29
The integrating sphere looks great, as long as you can deal with the height.

So far, I'm pretty happy with our DIY led systems. I may use one of the light boxes that Randy mentioned in another thread for a proofing scanner, one that takes a single shot of a whole negative.

Unfortunately Da Vinci lite requires a specific form of video card acceleration, which my system doesn't have. Photoshop does have a "match color" command.

As a number of people have suggested, making a compensating mask of some type wouldn't be too hard.

ludvig friberg
12-Feb-2015, 13:18
You can use Davinci on photos but its a bit cumbersome. Resolution is dependant on graphics memory and there is a ceiling around 5-6k on the more extreme hardware. My dayjob is in postproduction of movies and we use Davinci for colorgrading. Me and a friend who is a colorist made a project on Davinci with big photos. I made a script that sliced the picture into tiles and downscaled a copy for grading. In the timeline there would then be 1-6 slices and one downscale. Next 1-6 slices a downscale etc. The colorist worked on the downscale and then the grade was instanced to the tiles. All rendered out and then another script would assemble the tiles back. I dont think I would recommend this workflow if you are not a professional film colorist with a surface (http://www.tangentwave.co.uk/products_element.asp) and desperately want to use that tool also for photos. It was very good for us and we could really blaze through hundreds of photos and the client was very happy with the session. I would really love it if photo manipulation software moved into the physical realm like film and audio. I really miss having knobs and such to control the images.

Tin Can
12-Feb-2015, 13:43
Very interesting! Thanks for the info.

ludvig friberg
12-Feb-2015, 13:58
There is also stuff like this http://www.lightillusion.com/matchlight_ims.html but as with most special stuff in the film industry its quite expensive. I use some other software for calibrating cameras that is free like argyll cms together or sometimes instead of lightspace. If you want to do lens and sensor calibration I could dig in and try to find a free solution. Could you describe what you would like and your current workflow/problems?

Tin Can
12-Feb-2015, 14:20
Since I only do B&W LF film and primarily enlarge, I am not the most curious on this thread, but I follow the developments here. The scanner guys are most likely the most interested in correcting color, lens flaws and light source deficiencies.

Peter De Smidt
12-Feb-2015, 16:06
Capture One works well for that, but I haven't seen the need with my current light source. In addition, stitching software takes care of minor lens flaws, such as barrel or pin cushion distortion. The best lenses for this, though, have vanishingly small distortion at their specified magnifications. Currently, I use an APO Rodagon D 75mm f/4. Just for fun, I tried a Nikon 5x objective for their measurement microscope. It's very high quality, and the results might've been slightly better than with the Rodagon, but needing 400 frames to cover 4x5 is a little crazy, even for me.

I'd like to use Black Magic Lite for video, but it's not a big deal.

madumi
4-Mar-2015, 09:09
Just to throw out a few options for those with higher budgets:

Capture One recently released (Dec. 2014) software designed for museums/archival. Part of the software suite includes tools for conversion of film negatives captured by DSLR. The price tag is a bit astronomical, but I thought it might interest people here. Here's the link:
http://captureoneblog.com/capture-one-ch-8-cultural-heritage-announced/

Incidentally, their release pdf advises using a Kaiser Lightbox (17" x 19"). Here's a link to the non-dimmable version:
http://www.bhphotovideo.com/c/product/373548-REG/Kaiser_202492_17_x_19_Prolite.html

interesting stuff if you have loads of cash :-)

Peter De Smidt
4-Mar-2015, 09:53
Yikes!

Daniel Moore
4-Mar-2015, 11:08
Anyone interested can request a trial version of the Cultural Heritage version here:

http://dtdch.com/page/capture-one-ch

I'm plan to look into to any advantages it offers over C1v8 in practice. Not that I'll be shelling out for it.
I wrote them and linked to my scanner in hopes of persuading them to offer yet another version for the little guys.

Daniel Moore
10-Mar-2015, 20:18
I just learned that the Cultural Heritage version supports only Phase One backs. I was hoping to learn a thing or two that could be implemented in my current workflow with Capture One. Perhaps, one day.

madumi
11-Mar-2015, 19:09
Bummer. Do any of the tools in Cultural Heritage work with other camera files?

Daniel Moore
11-Mar-2015, 19:39
When I heard that they only support Phase One digital backs I stopped pursuing it. I did write them in support of adding Canon, Nikon, etc. support and pointed them to a site on using DSLR based scanners (http://www.dpbestflow.org/camera/camera-scanning) to emphasize the advantage of developing for DSLR scanners.

JasonF
22-Apr-2015, 20:48
A bit of a double question:

First, where is everyone now with a good light source for the DSLR Scanner? For example, how is the LED light sources turning out say to Xenon or Halogen type of lamps? It would seem that most lamps seem to fall under the 5000K color range. Whereas one can find LED's below and above the 5000K color range. It would seem some of the problems with the LED light sources are that they pulsate and don't have a high CRI. Since LED's seem to have a lower CLI, the attraction to a lamp source seems preferable to some.

Second, yet somewhat related, I'm of the impression that having a color temperature at or above 5000K for DSLR scanning color negatives is preferable to that of, for example, a 3300K color lamp? I'm not sure how true or not that is? But, it would seem the higher color temperature is helpful towards removing the orange cast in color negative film.

Related to the second question, I'm also a bit confused on the color filter (realizing this question is not best probably for this thread): some say the need for color filters are dead. But, I've read that for example one could change the color temperate by the use of a filter. For example, some say one can use a D80 filter (if i have that right) to convert the color temperature from 3000K to say 5000K? Others say that there's no point since this now can be done in post processing as long as RAW files are used from the DSLR.

drtebi
2-Jun-2015, 02:17
Hopefully this thread is still being watched and stays active, as I am just starting to make plans for a DSLR scanner...

A question regarding color negatives:
I have read through this entire thread, and did not see anybody mentioning the ColorPerfect plugin for Photoshop/Photoline, which is a dedicated plugin to convert color negatives to positives. While I haven't tried it yet with a DSLR scan, I have been using it exclusively for all my color negative scans, and find that the results are quite good. I think it's fair to assume that any color shifts I have experienced are most likely due to the fact that I haven't calibrated my (film-) scanner yet. Nevertheless, I have been wanting to not use ColorPerfect (because I run Linux and don't like switching back and forth just for this) and tried manual orange mask removal with a couple of different image editors, and I have to admit I finally gave up. While I was able to get good results at times, I could never apply the same settings for other images, and thus not achieve consistent results. Thus I wonder, wouldn't it be easier to just use one very good light source with even illumination optimized for slides, and then use the same light source for negatives but put the task of orange mask removal to a dedicated plugin? Just wondering if anybody has tried that.

And just in case you wonder—no—I did not just sign up for this forum to advertise for ColorPerfect! I shoot mostly 35mm and 6x7, but since my scanner (Minolta DImage Multi Pro) sometimes seems to crash, I investigated the DSLR scanning method and was quite impressed by some very crude tests from my Ricoh GXR with the macro lens and APSC size sensor. The other reason why I am after better scans is, that my modified Beseler King slide projector with a 4.0/250mm Schneider AV-Xenotar MC lens produces so much nicer images than my scans (in terms of color, shadow details etc.)... so I am now gathering information and there is a ton of great info on these forums, so I dared to sign up even though I don't do any large format photography.

Peter De Smidt
2-Jun-2015, 07:58
Hi Jason,

Nikon and Epson have used LEDs as the light source in some of their scanners, and I've been happy with the LEDs in my scanner, but then I scan 99% black and white film. A pwm dimming circuit can cause banding in the final scan at certain settings, but this can be gotten around. Sure, you can use lighting filters to change the color temp of a source. The big problem with halogen is the heat, especially since the light will be on for a couple of minutes, unlike in a darkroom enlarger. Xenon flashes do work, but if you're using speed lights consistency can be a bit of an issue, and Xenon sources aren't necessarily all that linear in output.

Drtebi,

There are adherents of Colorperfect on the forum. I predominantly scan black and white, though, and so I haven't looked into it.

Tom Monego
2-Jun-2015, 16:53
I use a Bessler slide duplicator with a copy stand, and a Nikon camera D300 right now, and a 55mm f2.8 Nikon macro. The light source can be strobe or or 3200k tungsten. I use the 4x5 adapter. In the long run I prefer a scanner. My Epson is great with 4x5 but terrible with 2 1/4 formats. For 35mm slides I have a Schneider 60mm duplicating lens I'll use with the Nikon.

Tom

drtebi
2-Jun-2015, 17:00
Hi Jason,

Drtebi,

There are adherents of Colorperfect on the forum. I predominantly scan black and white, though, and so I haven't looked into it.

Thank you for your response.
I will test the DSLR scanning of color negatives and conversion with ColorPerfect and report back once I get to it.

So what is the general consensus regarding color temperature for color slides? I assume 5800K daylight should be preferred for slides?

drtebi
21-Jun-2015, 05:58
Not sure if I should start a new thread, since this one is kind of old... anyway.

I am pretty far with my DSLR Scanner setup (mostly for 6x7 slides). There is one thing I am curious about, and one of you may have an answer to this.

I am comparing my DSLR scans (with a Nikon D810) to my Minolta Dimage Pro scans, and when I do 2×2 stitches I am getting very close to the same sharpness, sometimes better. I do however get less grain with the DSLR. It made me think that maybe what appears to be grain from the Minolta scanner is actually noise from the CCD. I don't think it comes from the anti-newton glass, because I am actually using the exact same negative carrier for the DSLR setup. Is it reasonable to believe that this "grain" is actually noise? Or is it maybe because my light box has a better diffused light?

Peter De Smidt
21-Jun-2015, 06:52
Consumer film scanners, such as those from Nikon and Minolta, exaggerate grain, especially with larger-grained film. For instance, many years ago, I owned a Nikon Coolscan V and a Canon 9950F flatbed. With fine-grained film, the Coolscan gave noticeably better scans than the Canon. With larger grained film, though, the results were the reverse. With Kodak High Speed Infrared, for example, the Nikon gave huge grain, so much so that image detail was degraded. The Canon did a much better job. This could've been do to sensor issues, grain aliasing, light source size.... someone made a diffusing screen for the light sources of the Minotla scanners and claimed greatly reduced grain. In comparing prints from both systems to those made with an optical enlarger, the scans produced by the flatbed were clearly more accurate grainwise than the Coolscan scanner for larger grained film.

So, yes, I expect that you're seeing scanner created noise in your Minolta scans.

drtebi
21-Jun-2015, 14:01
Thank you for confirming my suspicions.

I will work out the final details in my DSLR scanner and post results here soon. I still have a few questions, which I will probably find answers to here.

Reading all he DSLR Scanner posts of this forum certainly helped me a lot to make it all happen, so a big thank-you to all of you!

madumi
10-Jul-2015, 16:39
Hi guys,
I know it's not exactly a light source question, but I've been having some issues with a Canon 100mm 2.8 macro (non-L) lens having a slight horizontal vignette at the bottom (?). i.e. if I turn the DSLR upside down, the vignette goes to the top. Does anyone know if the L version of the Canon 100mm macro would be better... Or what lenses are people using for their scanning?
Thanks so much!

Peter De Smidt
10-Jul-2015, 16:51
I've used a 55mms Nikkor micro, a 75mms capo Rodagon d f/4, a 50mms Componon s, a Mitutoyo Mplan Apo 2x, .... All worked well. Each has a magnification where it works best. I prefer the Rodagon at 1x for scanning.

madumi
10-Jul-2015, 18:24
Thanks Peter for your reply... Any lenses closer to 100mm?

Oh, and while I'm at it, what RAW converters/software are people finding works best?

drtebi
10-Jul-2015, 21:35
The vignetting problem can also be fixed in software. It's an extra step, but works well.

CaptureOne has a built in fix for this, see: http://www.largeformatphotography.info/forum/showthread.php?87536-DSLR-Scanner-Light-Sources&p=1146865&viewfull=1#post1146865

But it can also be done with e.g. Photoshop. You need to take an image of the lightsource only, and later put this as a layer on top of your negative image; then put the lightsource image into "Divide" mode; you may have to adjust the levels a bit for the lightsource layer to prevent high-light blowout. It works really well though, just an extra step. For negatives I found that to be the only way to get an even light distribution.

PCC
11-Jul-2015, 19:35
Okay, I'm late to the discussion and I have not read all 19 pages of this discussion so I don't know if this had been mentioned previously or not (a search didn't turn up anything). Nichia has a pair of high power LEDs that produce both 92CRI and either 4500K or 5500K color temperature light (219 and 219B, respectively). Would an array of these LEDs produce the quality of light needed to do this?

madumi
12-Jul-2015, 11:22
Hi Peter,
I wondered if you could help me with a comparison, from what I was reading, the 75mms apo Rodagon has nice specs at 1:1, but the review mentioned slightly lower contrast to a "modern macro lens." Which brings me full circle, do you know how this lens would compare to a Canon 100mm 2.8L IS Macro... I'm gathering that the Canon lens might perform a bit better... any thoughts?
Thanks!

Daniel Moore
24-Jul-2015, 18:11
@PCC, as far as I know, no one has tested such LEDs so the jury is still out on CRI requirements/benefits. I did find a ribbon style LED strip that purported to be high CRI but upon powering it up it began smoking and I had to pull the plug on 'em. They were a chinese brand that seems to have disappeared from the face of the earth. Go figure.

Heat is a factor. The LEDs you mention are high output. They will generate a lot of heat in an array layout. You'd need to experiment with the quantity/spacing/size of lamp/diffusion to get the most even illumination for the intended format size. Peter and I have been using RGB LED ribbons from Lee Valley, branded Armacost. They are tightly spaced and low output so not that much heat to deal with. We can also dial in a neutral light relevant to the film type, compensating for color neg mask, tinted B&W, etc. if desired. I don't have any comparisons done with other LED types unfortunately. It's unclear at this stage also how significant CRI actually is to DSLR scanning. I did do a spectral response test and found that the lamp from my much loathed V700 (personal bias? : ) scanner had a pretty psychedelic set of peaks and valleys. Nothing like a black body spectrum such as an incandescent bulb. Not exactly scientific data I'm presenting here, is it :). Maybe it's of use.

Peter De Smidt
24-Jul-2015, 19:17
Hi Peter,
I wondered if you could help me with a comparison, from what I was reading, the 75mms apo Rodagon has nice specs at 1:1, but the review mentioned slightly lower contrast to a "modern macro lens." Which brings me full circle, do you know how this lens would compare to a Canon 100mm 2.8L IS Macro... I'm gathering that the Canon lens might perform a bit better... any thoughts?
Thanks!

I haven't used that lens, but I have used 55mm and 105mm Micro Nikkors. The Rodagon is better, which isn't at all surprising. The only lenses that I know of that are better at 1x are some of the super expensive Printing Nikkors. You can get higher resolution going past 1x, for instance my best lens for that is a Nikon 5x MM (Measuring Microscope) lens, but the number of frames needed to cover big film is prohibitive, and I doubt that most big film would benefit from such high resolution. I've tested it with 35mm Technical pan, and maybe I can see a slight difference from 1x at 300%..... Imo, dynamic range and freedom from noise are more important for scanning. At 1x with a good lens on a good dslr we have enough resolution.

Peter De Smidt
24-Jul-2015, 19:21
I agree with Daniel. Film scanners, even many professional ones, don't have high CRI light sources. My Cezanne doesn't. My Nikon Coolscan didn't. I expect that you just need good output at the wavelengths that the sensors are optimized for, but as Daniel says, it'd be fun to compare.

PCC
25-Jul-2015, 19:48
Daniel, if you want, PM me your snail mail address and I'll send you one, gratis, for testing.

Daniel Moore
25-Jul-2015, 20:54
How could I say no to that offer : ). PM on it's way.

Ludvig, who is no doubt occupied with his various and many projects, would have something to say about the value of high CRI. He went the mixing chamber route, which is viable with fewer LEDs at higher heat per unit.

I think Imatest could plot the frequency response of individual sensors. Hmm... I'll look into that. Their trial runs for 30 days, FYI. I've been holding off for something juicy to test it on.

Mapping illumination frequency/spectrum to optimum sensor receptiveness should have benefit.

PCC
26-Jul-2015, 22:47
@PCC, as far as I know, no one has tested such LEDs so the jury is still out on CRI requirements/benefits. I did find a ribbon style LED strip that purported to be high CRI but upon powering it up it began smoking and I had to pull the plug on 'em.

Heat is a factor. The LEDs you mention are high output. They will generate a lot of heat in an array layout. You'd need to experiment with the quantity/spacing/size of lamp/diffusion to get the most even illumination for the intended format size. Peter and I have been using RGB LED ribbons from Lee Valley, branded Armacost. They are tightly spaced and low output so not that much heat to deal with. We can also dial in a neutral light relevant to the film type, compensating for color neg mask, tinted B&W, etc. if desired. I don't have any comparisons done with other LED types unfortunately. It's unclear at this stage also how significant CRI actually is to DSLR scanning. I did do a spectral response test and found that the lamp from my much loathed V700 (personal bias? : ) scanner had a pretty psychedelic set of peaks and valleys. Nothing like a black body spectrum such as an incandescent bulb. Not exactly scientific data I'm presenting here, is it :). Maybe it's of use.

If you are using this for black and white copying then it's not going to make a difference what CRI the light source puts out. For color you need as much as possible. From personal experience comparing a standard white LED to a high CRI Nichia the reds stand out far better. You'd think that a white LED, which should be representative of all colors , would show all colors equally well but I am not seeing that. Most low CRI LEDs (65-ish CRI) are really blue LEDs with a phosphor that converts the blue light into white light and this white light is very weak on the red side of the spectrum. Red colors appear dull to my eyes with those LEDs while a high CRI LED shows them quite well.

Most white LEDs require approximately 3.2VDC at up to 1.5 amps except for those silly little 5mm ones that cannot be attached to a heatsink. Above 350 milliamps heatsinks are essential to long LED life. Below this drive level you're relatively safe. Heat is still being generated, but it's far less than at higher drive levels. Obviously, higher drive levels give you more light but these LEDs are at their most efficient at around 50mA or so (this varies from model to model).

Incandescent lights are 100CRI. They're terribly inefficient and produces heat in the form of infrared radiation. LEDs produce heat through its contact patch on the MCPCB that it's attaches to. The light has almost no infrared radiation. You can put your hand in front of a 2000 lumen flashlight and it's warm. A 1000 lumen incandescent can light paper on fire at close range to the lens. In a light box I'd rather run a copper strip to pull heat away from the emitters than to have the heat come through the negative that you are scanning. The entire box will heat up from the bulb.

Using a high CRI LED will not give you the color saturation that an incandescent bulb will give you but it won't be bad, neither. A standard low CRI LED will give dull reds and nice blues that you might be able to salvage in post but I'd like to avoid that as much as possible.

ludvig friberg
27-Jul-2015, 03:00
As I have stated before I have found the best method to be a Integrating sphere. That makes it much easier to have many different lightsources for testing and also makes it possible to mix them for different media. It would be interesting to test something like solux halogens against led (http://www.solux.net/cgi-bin/tlistore/infopages/solux-more.html). Biggest problem with normal incandescent is for negative color film, the orange cast together with a warm light makes it very problematic without heavy filters. Also it would be interesting to take 10 or so different white high cri leds and mix them in a sphere to see if perhaps they even out each other. One other nice thing with led is the possibility to balance the r,g and b to the native response in the sensor. Meaning less noise in channel x. And to use it for exposure time like a flash, that way I can easy capture HDRI, I do that for my motion film scanners. And if wanted a separate IR channel can be made if the camera is modified, however that changes the focus and makes everything a bit more challenging.

Daniel Moore
4-Aug-2015, 22:45
Back on the 26th of Oct 2012, in this thread (yikes!) Struan Gray wrote:

--------------------------------
"The beauty of LEDs is that you can choose three wavelengths which as much as possible avoid cross-contamination by avoiding the portions of the dye absorbance spectra which overlap. You then adjust the brightness of each type of LED (with modulation, or by adding more or less LEDs to the source) so that each channel gets as much light as it can take without being over-exposed. Post-capture you adjust the strength of the relevant channels *downwards* to balance for grey and overall gamma.

If the spectral absorbances of the dyes in the film overlap at all wavelengths, there will always be *some* cross contamination. But with better signal to noise in the blue channel you are in a better position to do something about that with further processing.

The central point is that just because colour negative film was optimised for analogue printing with an incandescent light source, it doesn't mean that will be the best light source for capture with a DSLR."

------------------------------

This echoes Ludvigs statement above "One other nice thing with led is the possibility to balance the r,g and b to the native response in the sensor."

I'm not suggesting the RGB LEDs Peter D. and I are currently employing are that, specifically, tuned to a DSLR sensor, but I do want to suggest that high CRI may not be the primary target for DSLR scanning. In fact, I have read about the poor color response to tungsten lighting that DSLRs can suffer. I can't find that info at the moment (there is certainly such a thing as too many bookmarks) but I've seen it for myself. Black body spectrum might be perfect for color slide film but very likely isn't perfect for other film types.

Mind you, I'm no scientist. But even they can't always agree : ).

Final note for the night. Anyone interested in developing a light source would do themselve a huge favor by reading the absolutely phenomenal input made by some very knowledgeable folk through out this thread. Start at the beginning, it's a hell of a ride, as I reminded myself for the last two hours : ).

drtebi
16-Aug-2015, 18:06
As I have stated before I have found the best method to be a Integrating sphere. That makes it much easier to have many different lightsources for testing and also makes it possible to mix them for different media. It would be interesting to test something like solux halogens against led (http://www.solux.net/cgi-bin/tlistore/infopages/solux-more.html). Biggest problem with normal incandescent is for negative color film, the orange cast together with a warm light makes it very problematic without heavy filters. Also it would be interesting to take 10 or so different white high cri leds and mix them in a sphere to see if perhaps they even out each other. One other nice thing with led is the possibility to balance the r,g and b to the native response in the sensor. Meaning less noise in channel x. And to use it for exposure time like a flash, that way I can easy capture HDRI, I do that for my motion film scanners. And if wanted a separate IR channel can be made if the camera is modified, however that changes the focus and makes everything a bit more challenging.

Regarding Solux Halogen bulbs:
I have built a DSLR Scanner with a lightbox that uses a Solux Halogen bulb. I am quite satisfied with the results. The colors are great, a bit on the warm side, but that's easy to edit out (e.g. much easier than a color cast).

What is much more difficult with a halogen light source is to get an even illumination. Eventually I decided to solve that problem with software. At each scanning "session" I also take an image of the light source alone, with no negative/positive. I then use this as a layer in PhotoLine (similar to Photoshop) and set the layer to "divide". That layer usually also needs a bit of exposure adjustment, to avoid overexposure after the division adjustment.

A similar technique was mentioned in this thread here:
http://www.largeformatphotography.info/forum/showthread.php?87536-DSLR-Scanner-Light-Sources&p=1146865&viewfull=1#post1146865

Here are a few links to my results:

Fujifilm Reala 100 shot with Fuji GA670: http://1drv.ms/1TIa37L

Fujifilm Superia 200 shot with Yashica Electro 35 GSN: http://1drv.ms/1PguOEx

Fujifilm Reala 100 shot with Plaubel Makina 670: https://www.flickr.com/photos/drtebi/albums/72157653529648714

And here a couple of shots taken with the Plaubel Makina 670 on Fujifilm Provia 100F:
https://www.flickr.com/photos/drtebi/19044135543/
https://www.flickr.com/photos/drtebi/18980441304/

My DSLR is a Nikon D810, I use the ColorPerfect plugin for negatives, and I do a tiny bit of post editing in LightZone. When comparing my results to those of my Minolta Dimage Multi Pro film scanner, I have to say the DSLR does a much better job. The scanner can still resolve more detail, but the light source of the scanner is definitely not as nice as the halogen bulb. I also get a lot less grainy-looking images, which I believe is due to the better diffusion of the light with the DSLR setup.

Please don't hesitate to criticize the outcome of these images, technically speaking (I am no professional photographer...). I would love to hear what you think.

Peter De Smidt
30-Aug-2015, 09:53
Charles Krebs has a good DIY write-up on making high CRI LED fixtures. See: http://www.photomacrography.net/forum/viewtopic.php?t=27265&start=0

LED is a Bridgelux COB, "Decor Ultra Vero 10", with a CRI of 97, part number: BXRC-30H1000-B-2 .

Joseph_B
20-Oct-2015, 02:40
Hello thanks for adding me to the forum - I hope this thread is still active, so I won't make a new one to ask this. I have a couple of questions to ask you guys, as I have just embarked on this process myself.

My setup: Nikon D810 - Tokina 100mm macro - Kaiser Rs2 copy stand - Artograph A920 LED light pad - 6x7 neg carrier.

My thoughts findings so far - I have found that I easily clip the red channel in the camera when taking the photograph on the DSLR of the negative. It makes me wonder would using a blue thread on filter on the lens help? I also assume that clipping the red channel gives you less room to manoveure later when you are trying to convert your image into a positive using color perfect, or photoshop or whatever.

If I used a filter, I think that I would reduce light by a couple of stops, meaning that I would have to have a longer exposure? Is this a problem? I am already at about 1/5s a second, iso 64 - shooting on the copy stand

And does a flash give less peaks across the spectrum than an LED light?

Does anyone think that the LED light source that I am using is not as suitable as using flash and a diffusion box. With flash, the benefits would probably be a stronger light source and so better exposure times (minimising potential vibration, or trouble moving around?) But I think flash might give more of an uneven light spread compared to the Lightbox?

To recap
- Should I use a filter on my DSLR for capture?
- Will a flash work better than an LED lightbox
- What software do you guys use to conver? ColorNeg by ColorPerfect, or Photoshop, or Vuescan?

Cheers,

drtebi
20-Oct-2015, 18:07
- Should I use a filter on my DSLR for capture?

I don't think that would be a good idea. You will probably make the conversion process more difficult than without.
I am using ColorPerfect as well, and am getting really nice results. I am using a Solux halogen light bulb though, and with my D810 I am setting the color temperature manually to 4700K.



- Will a flash work better than an LED lightbox

I haven't tried a flash, but in my earlier experiments I did use an LED lightbox similar to yours. Then I did a lot of reading about light sources, and my conclusion was, that a "black body" (edison-type light bulb, halogen lightbulb etc.) would give me the best colors. Especially the warmer colors of the spectrum are looking much more natural to me with a halogen bulb.

It is a bit tricky to evenly diffuse the light of a halogen light bulb, but it is possible to remove any irregularities in post processing. You can do this by taking an image of the light source alone, and then put that image as a layer on top of your negative image. Then put the light source image layer into "Divide" and, if necessary, adjust the histogram of the light source layer to avoid over-exposure. This technique works great for me, here are some examples:
6×7: http://1drv.ms/1TIa37L
35mm: http://1drv.ms/1PguOEx

But if you want to stick with the LED lightpad, I think the most crucial thing is, to set the color balance right. Maybe try to do that with a positive (slide), which will make it easier to judge the color balance.

I also noticed that not all film is easy to scan. While I got great results with Fujifilm Reala, Kodak Portra 160 looked really off.



- What software do you guys use to conver? ColorNeg by ColorPerfect, or Photoshop, or Vuescan?

I use ColorPerfect. It usually gives me great results without changing any of its settings (except the film type).

I have tried many other methods to convert a negative to a positive, and while I did get nice results at times, I could never repeat the same process on other negatives to get consistent results. Especially not once you change to a different film. I really wanted to use my own custom conversion, or just another program, but I gave up... ColorPerfect just does it better and faster than anything else I have tried.

By the way, ColorPerfect also works with PhotoLine. PhotoLine is more or less like Photoshop, but costs much less.

For final post editing (e.g. after the conversion), I use LightZone. I really like that program despite the couple of quirks it has. It makes post editing very quick, and I find the modules very smart and powerful, yet easy to use. It's not for everyone, but worth a try. Oh, and it works on Linux, too (Java-based).


Another thing I would like to mention... stitching can get you more detail if you get it right. I have my lightbox mounted on an X-Y table, and some images I scan 2×2 and then stitch the four pictures together with Image Composite Editor, which is free, easy to use, and most of the time works just perfectly.

Here is a picture of my setup:
141214

If you would like more info on my setup, just ask here.

Cheers,
DrTebi

ropel
15-Nov-2015, 03:52
I have been following along on this topic - quite a read by now :-)

I'm looking to work towards a scanner setup as well, hopefully including a nice XY table.
My current set-up is a Canon FD bellows with duplicator, Canon FD 50mm macro lens and Sony A7 attached.
Playing around with ColorPerfect, which so far seems a very good piece of software indeed.

So many messages on the light sources that I am not quite sure what direction to go.
Lots of posts aim at high CRI, but since I'm primarily focussing on B&W, that probably is not my biggest concern.
Currently I'm using my tablet, and that makes me think in the direction of a lightbox (e.g., http://www.kaiser-fototechnik.de/en/produkte/2_1_produktanzeige.asp?nr=2447)
Seems a good option for even illumination, but I'm unsure if the light output will be sufficient? (My tablet certainly is not, slow shutter speeds > 1 sec required to get the shot at f8).
Can anyone share experience in lightbox vs tablet light output?

If a lightbox turns out to be insufficient, I'm in doubt about halogen vs LED.
Any recommendation for B&W setup at reasonable price?

Thanks!

Roy

drtebi
20-Nov-2015, 12:03
I have been following along on this topic - quite a read by now :-)

I'm looking to work towards a scanner setup as well, hopefully including a nice XY table.
My current set-up is a Canon FD bellows with duplicator, Canon FD 50mm macro lens and Sony A7 attached.
Playing around with ColorPerfect, which so far seems a very good piece of software indeed.

So many messages on the light sources that I am not quite sure what direction to go.
Lots of posts aim at high CRI, but since I'm primarily focussing on B&W, that probably is not my biggest concern.
Currently I'm using my tablet, and that makes me think in the direction of a lightbox (e.g., http://www.kaiser-fototechnik.de/en/produkte/2_1_produktanzeige.asp?nr=2447)
Seems a good option for even illumination, but I'm unsure if the light output will be sufficient? (My tablet certainly is not, slow shutter speeds > 1 sec required to get the shot at f8).
Can anyone share experience in lightbox vs tablet light output?

If a lightbox turns out to be insufficient, I'm in doubt about halogen vs LED.
Any recommendation for B&W setup at reasonable price?

Thanks!

Roy

I think your best bet is, and what I usually do, to try the simpler methods first; then, depending on your results, upgrade what you think needs improvement.

In the beginning I have used a cheap lightbox (which was actually for tracing, rather than slides), and I must say the results were quite satisfactory. With a lightbox you will also have much less problems with diffusion, since most lightboxes will have several LEDs inside, and a large center area with good and evenly diffused light.

When I switched my light source to the Solex halogen, I felt that I could get warmer results, more natural looking ones (for color that is, of course). But the proper diffusion of light was extremely difficult, so in the end I sorted that problem out in the post-processing, by overlaying an image of the plain light-source in inverted mode etc.

Regarding an XY table: What size of negative are you planning to scan? If you are working with 35mm, it's probably not worth it, since you would need a macro lens with more than 1:1 magnification, which in itself may degrade the quality of your result (in other words, with a dedicated 1:1 macro and one-shot scans you would get better results). For medium format, it may be worth it. I noticed a great improvement in detail when working with black and white negatives. For color negatives and slides, the improvement was rather small, and due to the extra time spent using 4 shots and stitching, I often just sticked with the single shot (which was quite good already).

I think your best bet for now is, to replace your light source. A tablet doesn't have diffused light, so it would need an additional diffuser to produce properly diffused light, which in turn will give even less output. Try a lightbox with good CRI and good diffusion. When choosing a lightbox, be sure that it fits well within your setup physically. Especially if you want to add an XY table later on, a large lightbox may be problematic.

I hope this helped you out a bit... these are of course only my own opinions, hopefully other people may add some of their own knowledge.

ropel
29-Nov-2015, 09:05
Thanks a lot! Very helpful indeed. I'm mainly digitizing B&W on 35mm and medium format.

For light I will keep an eye out on decent lightbox. Seems more convenient as well.

The one shot tip is for 35mm is very welcome. I was hoping to go beyond 1:1 (even with extension tubes), but that might not the way to go. Have to reconsider how to gain the best resolution.

Thanks again.

Peter De Smidt
29-Nov-2015, 16:45
My setup uses a 75mm Rodagon D f/4, which is optimized for 1x magnification. I've tried using a Mitutoyo APO M-Plan 2x objective, and a Nikon MM5x objective, each at their rated magnifications. Even using a negative of 35mm tech pan shot with the camera on a huge tripod, mirror lock up, and a prime lens at it's optimum aperture, it was near impossible to see a visual difference in the resulting files scanned at the corresponding magnifications. Using a chrome on glass resolution slide was another matter, with the expected rise in resolution for each of the steps up in magnification, but that wasn't the case for negatives shot in a camera. So in my system there is no need to go above 1x. That still allows a good-sized print with 35mm, and the process is very fast, as no stitching is involved.

joelkphoto
10-Dec-2015, 05:06
I've been using my ipad mini as a light source for BW negs. I have a Negaflat raised up 2 inches off the ipad. On full brightness and a blank page open I get 1/50th at 5.6 and ISO 400 with my D600 and a tokina 100mm macro. Works pretty well! Check my flickr page for results. Most images are 4 shot stitches.

drtebi
10-Dec-2015, 23:48
Thanks a lot! Very helpful indeed. I'm mainly digitizing B&W on 35mm and medium format.

For light I will keep an eye out on decent lightbox. Seems more convenient as well.

The one shot tip is for 35mm is very welcome. I was hoping to go beyond 1:1 (even with extension tubes), but that might not the way to go. Have to reconsider how to gain the best resolution.

Thanks again.

Unless you are planning to do some huge prints, I think you will be quite please with the results and resolution of 1-shot 35mm DSLR scans. A good macro lens should do the trick.

Here are some examples to give you an idea. All images are reduced in size to 2400 pixels in height (my monitor). You can click the "download" link to get the original:

http://1drv.ms/21TKlCk

All were shot with a Yashica Electro 35 GSN on Fujifilm Superia 200 and scanned with a Nikon D810 with a Nikon 60mm f/2.8 AF-D Micro lens, using my previously described setup.

Ted Baker
6-Feb-2019, 13:39
Has anyone used a portable flash ideally a nikon sb-26 (that is what I currently have) as a light source with stitching?

Specifically how consistent is the flash output, with regard to stitching the image. If you used a different battery power flash I am still interested in how consistent it was.

I want to build a light source to trial a few ideas I have, that need a powerful light, but I don't want to waste my time if stitching is not going to work with a flash.

rdeloe
6-Feb-2019, 14:30
I asked about light sources over at FredMiranda and user Rico posted a picture and description of his flash-lit approach. Have a look if your answer is there:

https://www.fredmiranda.com/forum/topic/1576100/0#14702562


Has anyone used a portable flash ideally a nikon sb-26 (that is what I currently have) as a light source with stitching?

Specifically how consistent is the flash output, with regard to stitching the image. If you used a different battery power flash I am still interested in how consistent it was.

I want to build a light source to trial a few ideas I have, that need a powerful light, but I don't want to waste my time if stitching is not going to work with a flash.

Ted Baker
6-Feb-2019, 15:26
I asked about light sources over at FredMiranda

Thanks, I had look, none of those guys are using stitching AND flash.

rdeloe
6-Feb-2019, 15:34
Thanks, I had look, none of those guys are using stitching AND flash.

Is your concern that between frames the flash will have inconsistent output? I would have thought a good flash should produce a consistent amount of light. Then again, I could see even the same model of flash performing differently depending on age and condition.

I suppose you could test yours out by shooting a dozen frames of the same subject in fairly quick sequence and checking to see whether or not the exposure at the same point in those frames is the same.

Anyway, that's all I got for you. I went with the LED light source approach: https://www.largeformatphotography.info/forum/showthread.php?150162-Camera-scanning-on-the-cheap-an-example-approach

Larry Gebhardt
6-Feb-2019, 15:53
I'm a fan of using a color head for scanning color negative film. It lets you remove the orange mask and gets all three channels exposed the same amount (histogram peaks align). That lets you expose to the right and have much less noise in the highlights when you invert.

Peter De Smidt
6-Feb-2019, 19:36
I used an SB-28 for my first light source. There will be some variation. Make sure to use fresh batteries. Make sure to allow longish time between flashes, to make sure that the flash is completely charged. If you go too fast, the tube will heat up, and it will lower output. I would be surprised if there was enough difference between frames to cause a stitching problem, though.

Ted Baker
7-Feb-2019, 03:21
Peter,

Do you have a copy of the design of the light box you used with the flash? I was thinking of buying an old color head, and modifying it. But my design needs three light sources (a beam splitter will suffice). I understand there a few high end mixing heads that work this way, but not easy to find or cheap, and a pity to modify such equipment. I think they are called additive lamphouses.

In any case if it works I would like to produce something that others can build anyway.

Peter De Smidt
7-Feb-2019, 08:50
Ted, I had a three-bulb additive color head on my Philips PCS2000 enlarger. I might have it still...hm.

Here are some pictures of my first dslr scanner light source:

https://www.dropbox.com/s/kfqfvpbhykel54u/LSP1_Flash.jpg?raw=1

https://www.dropbox.com/s/p4v7lqjgsx1ho1f/LSP1_LED.jpg?raw=1

https://www.dropbox.com/s/2e3j67uj4q2hrzc/LSP1_NoLight.jpg?raw=1

Ted Baker
7-Feb-2019, 09:14
Thanks I saw that earlier, you mentioned a LSP-2?


Ted, I had a three-bulb additive color head on my Philips PCS2000 enlarger.

That one is 6x6, ideally 4x5 would be great but it would be interesting to get some design ideas. I had look a on the net to see how the diffusion box works, in some of these enlargers.

Richard Martel
15-Sep-2019, 17:06
i Have not read the entire thread, so please excuse me if it has been previously mentioned. What about using a Wacom Tablet with a diffuser made from translucent white plexiglass over the screen of the tablet to keep from resolving the pixels. I think the largest tablet is around 20x12 inches. Just a thought.
Cheers Richard

Peter De Smidt
15-Sep-2019, 17:15
I currently use a Pixel P50 LED light panel. https://www.amazon.com/Bi-Color-3000-5800K-YouTube-Self-Portrait-Shooting/dp/B07K9K92ZS

Richard Martel
15-Sep-2019, 18:06
Thanks for that link Peter. I could not find the length and width dimensions though. How do you find the distribution of light across the panel?
Cheers Richard

PS, Peter, where can I find the Giant DSLR Scanning thread that is see quite oftentimes mentioned....Thanks R

Peter De Smidt
15-Sep-2019, 18:40
It is an edge-lit panel, and so it doesn't have the hot spots of one where each of the LEDs is visible. I used diffusion sheets on the panel to equalize the middle and edges inside a white pvc box with an acrylic diffuser on top. After this is done, it's very even, and the brightness and color quality are very good. It's just wide enough to work ok with 8x10. It's plenty long.

For links to the other threads, see the first page of this thread.

Richard Martel
16-Sep-2019, 19:28
Great! Thanks Peter.
Cheers, Richard