-
DSLR Scanner: Light Sources
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 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,
Lenses,
Negative-Stages,
Light Sources,
Stitching-and-Blending-of-Images,
Cameras-and-Camera-Control-Software.
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.
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.
-
Re: DSLR Scanner: Light Sources
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/a...P1_NoLight.jpg
http://i955.photobucket.com/albums/a...t/LSP1_LED.jpg
http://i955.photobucket.com/albums/a...LSP1_Flash.jpg
http://i955.photobucket.com/albums/a...rcedrawing.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.
-
Re: DSLR Scanner: Light Sources
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
It would be nice for theses threads to be made 'sticky'.........
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
jon.oman
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.
-
Re: DSLR Scanner: Light Sources
Just noticed this set of threads!
I have a Rosco LitePad 6x6 and it is described as ~6000K with a CRI of 93. 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 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, 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
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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...
-
Re: DSLR Scanner: Light Sources
Sounds good. I haven't down any work with slides yet.
-
Re: DSLR Scanner: Light Sources
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
-
Re: DSLR Scanner: Light Sources
Sounds like you're making some good progress.
-
Re: DSLR Scanner: Light Sources
Rick, have you considered trying this type of LED back light?
http://www.edmundoptics.com/products...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.
-
Re: DSLR Scanner: Light Sources
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
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
peter ramm
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
-
Re: DSLR Scanner: Light Sources
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
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
ludvig friberg
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
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
rdenney
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.
-
Re: DSLR Scanner: Light Sources
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
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
I based my source on a De Vere light mixing box. The lighted area is approximately 250mm x 250mm.
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
ludvig friberg
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
Ludvig,
I'll take some pictures soon, both of a De Vere unit and of my light source.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
Serge S
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.
-
Re: DSLR Scanner: Light Sources
Quote:
Originally Posted by
Peter J. De Smidt
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
-
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
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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
-
Re: DSLR Scanner: Light Sources
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.)
-
Re: DSLR Scanner: Light Sources
Very exciting developments, Ludvig. Please tell us more about your design so far.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
i have absolutely nothing to contribute to this fred, except maybe a bit of cheering from the side, GO YOU MAD BASTARDS!!!!!
-
Re: DSLR Scanner: Light Sources
-
Re: DSLR Scanner: Light Sources
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?
-
Re: DSLR Scanner: Light Sources
Actually, my computer screen is just shy of 14", so wont work...oh well....other sources?
-
Re: DSLR Scanner: Light Sources
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.
Quote:
Originally Posted by
ludvig friberg
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.
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
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?
-
Re: DSLR Scanner: Light Sources
Let me ask some boundary condition questions first:
Area to light ?
Sensor technology ?
Line sensor or area sensor ?
Quote:
Originally Posted by
Daniel Moore
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?
-
Re: DSLR Scanner: Light Sources
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
-
Re: DSLR Scanner: Light Sources
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!
-
Re: DSLR Scanner: Light Sources
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.
-
Re: DSLR Scanner: Light Sources
My light source currently has a light emitting area of 4.25" square. I wouldn't want to go smaller than that.