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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Alan Klein
If you want to scan without any adjustments with Epson Scan, uncheck all boxes. Then click on the Configuration button at the bottom. When it switches to the Configuration page click on the No Color Corrections. The scan. Then do all your changes on the resultant "flat" file with your post processing program.
Eureka ! That works nicely.
Given what Ted has pointed out, I guess it shouldn't be too surprising that the VueScan raw file and the Epson Scan file made with no color corrections don't match exactly.
Scanning a B&W negative, the Epson version comes out as a positive where some kind of gamma adjustment has already been applied. The VueScan raw version comes out as a negative and requires a Gamma 2.2 adjustment followed by an inversion to positive. The Epson version is "snappier", while the VueScan version is flatter. Which version is a more faithful rendition of the negative, who can say ?
When scanning a reflective image with Epson Scan, there's a discernible difference between a scan made with "No Color Corrections" and one made where we zero-out the Histogram Adjustment settings... Oh well :rolleyes:
Perhaps this thread should be renamed to "how to minimize tonal adjustments".
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
Eureka ! That works nicely.
Given what Ted has pointed out, I guess it shouldn't be too surprising that the VueScan raw file and the Epson Scan file made with no color corrections don't match exactly.
Scanning a B&W negative, the Epson version comes out as a positive where some kind of gamma adjustment has already been applied. The VueScan raw version comes out as a negative and requires a Gamma 2.2 adjustment followed by an inversion to positive. The Epson version is "snappier", while the VueScan version is flatter. Which version is a more faithful rendition of the negative, who can say ?
When scanning a reflective image with Epson Scan, there's a discernible difference between a scan made with "No Color Corrections" and one made where we zero-out the Histogram Adjustment settings... Oh well :rolleyes:
Perhaps this thread should be renamed to "how to minimize tonal adjustments".
I believe you're right that you still have control of the Levels (black and white points) even when No Color Correction is checked off. Going back to the COnfiguration page, there are setting for controlling the gamma and other stuff other than No Color Correction or color correction. I don;t know anything about how they work though.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Alan Klein
I believe you're right that you still have control of the Levels (black and white points) even when No Color Correction is checked off. Going back to the COnfiguration page, there are setting for controlling the gamma and other stuff other than No Color Correction or color correction. I don;t know anything about how they work though.
You're right that the slider can still be adjusted, but I just tested both a reflective and negative scan: no matter how we set the Auto Exposure Level slider, the resulting images are indistinguishable. Once we select No Color Correction, it doesn't matter what else we do: everything else is disabled and greyed-out. (I suspect the fact that the Auto Exposure Level slider still slides, is an oversight: the software developer forgot to disable the slider.)
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
no matter how we set the Auto Exposure Level slider, the resulting images are indistinguishable.
I think you misunderstand the purpose of exposure in this context. If I was to look at a series of photographic prints, printed traditionally, with different camera exposures how would I tell the difference? How would a picture taken at f16 and 1/500 on hp5 look different from f8 at 1/500?
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
I think you misunderstand the purpose of exposure in this context. If I was to look at a series of photographic prints, printed traditionally, with different camera exposures how would I tell the difference? How would a picture taken at f16 and 1/500 on hp5 look different from f8 at 1/500?
We would see a corresponding difference in the density of the resulting images.
I was merely observing that once we choose the option to disable all color correction, any other changes we make are ignored.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
We would see a corresponding difference in the density of the resulting images.
In the prints? Expand the example take a series of shots from -5 stops underexposed through to +10, print say a mid tone in the picture at the same density. Would the prints all look the same? would some look very similar to the "correct" exposure?
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
I think you misunderstand the purpose of exposure in this context. If I was to look at a series of photographic prints, printed traditionally, with different camera exposures how would I tell the difference? How would a picture taken at f16 and 1/500 on hp5 look different from f8 at 1/500?
But if exposure was changed then scanning speed would also change, so it would be noticed...
IMHO there is a way to check that the scanner is actually bypassing all tonal adjustments, this is scanning an Stouffer wedge (T2115 or T4110). Then knowing the calibrated densities we can calculate (MS Excel) the theoric progresion related to lowest density, or from a mid grey, the calculated theoric values have to match a linear scan reading for each wedge step, every 2 wedge steps (or 3 in the T4110 case) the reading should be the half or the double, the reading can be seen with Ps, Information panel shows the value for the spot we point with the mouse...
Exposure should be adjusted to a level that it does not saturate the CCD in an empty area, but this perhaps is not enough to get an accurate reading for deep shadows in slide film, no problem with negative film (BW or color) , but slides may have very dense areas that (if important) may require Multi-Exposure (single pass or multiple pass) to get an accurate reading, still the calculated reading should be linear.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Pere Casals
But if exposure was changed then scanning speed would also change, so it would be noticed...
Which is what we established vuescan offers and you can measure it, epsonscan does NOT have a manual method to vary the exposure...
Quote:
Originally Posted by
Pere Casals
IMHO there is a way to check that the scanner is actually bypassing all tonal adjustments, this is scanning an Stouffer wedge (T2115 or T4110). Then knowing the calibrated densities we can calculate (MS Excel) the theoric progresion related to lowest density, or from a mid grey, the calculated theoric values have to match a linear scan reading for each wedge step, every 2 wedge steps (or 3 in the T4110 case) the reading should be the half or the double, the reading can be seen with Ps, Information panel shows the value for the spot we point with the mouse...
That will work for positive scan, it won't work for a negative or at least it shouldn't because you DO want a tonal adjustment.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
In the prints? Expand the example take a series of shots from -5 stops underexposed through to +10, print say a mid tone in the picture at the same density. Would the prints all look the same? would some look very similar to the "correct" exposure?
The prints would not look all the same. Some would be similar to the correct exposure.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
That will work for positive scan, it won't work for a negative or at least it shouldn't because you DO want a tonal adjustment.
For WB in reality I dont wan't tonal adjusment for the negatives, in any case I prefer to shape the curve with Ps. I always scan with V850 in that way, taking all linear range .
For WB I'm working with the possibility to take a linear scan and then using PS to preview the effect of selective color masking http://phototechmag.com/selective-ma...onal-darkroom/
The idea is painting in a layer with contrast filter colors over the linear image. Then a LUT should convert from the coloured image to a soft-proofing image that would predict the result if printing the coloured mask and using it sandwiched with the negative in the enlarger.
The challenge is the calibration software that takes sensitometric tests and generates the LUT. I clarify, the LUT converts the linear image painted over with magenta to yellow colors to a greyscale showing the reflective density predicted for each spot.
This is to design a color mask WYSWYG to get local contrast control in the darkroom, and to print that mask with a cheap inkjet. The sensitometric response is to be measured with printed color samples, made with the same inkjet and using same colors from PS...
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
The prints would not look all the same. Some would be similar to the correct exposure.
Exactly and you are an experienced photographer, so you can imagine why manual control is not offered in epson scan, and indeed why an automatic function can do a very good job of the required task. It's not clear in epson scan what high or low even means, or how it varies the automatic exposure calculation, if at all. Indeed it may just be a mistake.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Pere Casals
For WB in reality I dont wan't tonal adjusment for the negatives, in any case I prefer to shape the curve with Ps. I always scan with V850 in that way, taking all linear range .
I am sure that's what everyone wants, but that is not what happens. If I print a Black and white print on grade 2 paper, I WILL get a tonal adjustment from the negative, and that is what I want and that IS THE WAY it is designed. (any grade actually).
If I want to process a roll of negative film as a positive, other than the reversal step (bleach/2nd developer), what else do you need to do? ;)
I hope you understand I am not criticising your methods in anyway, I am just point out a discrepancy in your description.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Alan Klein
If you want to scan without any adjustments with Epson Scan, uncheck all boxes. Then click on the Configuration button at the bottom. When it switches to the Configuration page click on the No Color Corrections. The scan. Then do all your changes on the resultant "flat" file with your post processing program.
That was always the goal with Epson scanners, Alan; get a neutral scan, flat as can be, so that one could have more post-processing options available in PS/LR.
I've since moved to an Eversmart Pro, but the scanning goal is the same: neutral, flat, unsharpened file that can be tweaked as much as I like in post.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ari
That was always the goal with Epson scanners, Alan; get a neutral scan, flat as can be, so that one could have more post-processing options available in PS/LR.
I've since moved to an Eversmart Pro, but the scanning goal is the same: neutral, flat, unsharpened file that can be tweaked as much as I like in post.
I have the Eversmart Supreme as well and I agree with Ari, 16 bit also Gamma 2.2 for BW 16bit RGB (I use Adobe 1998) and keep within the scanners native resolution, rather than trying to make bigger files.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
A D750 and many other cameras have a setting for Flat, Neutral, Standard, Vivid, Monochrome, Portrait and Landscape.
The video guys want 'Flat' for the best in post.
I do like this thread. :)
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Ken, thank you for your webpage explaining scanning! It's good and this thread only helps everyone figure things out also.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
I am sure that's what everyone wants, but that is not what happens. If I print a Black and white print on grade 2 paper, I WILL get a tonal adjustment from the negative, and that is what I want and that IS THE WAY it is designed. (any grade actually).
If I want to process a roll of negative film as a positive, other than the reversal step (bleach/2nd developer), what else do you need to do? ;)
I hope you understand I am not criticising your methods in anyway, I am just point out a discrepancy in your description.
There is no discrepancy...
The real scene or what is recorded in the negative can have more range than what the display medium allows, a paper has 1:100 aprox static contrast. So a common situation is having to compress (or cut off) more or less the shadows and the highlights to have mids taking enough dynamic range. This can be performed by the scanner software automaticly or it can be adjusted manually with Ps. For important shots I prefer to adjust manually what's in the toe and what's in the shoulder, tonal adjustment with PS is flexible and easy, single key point is having a 16 bits tiff file to avoid banding.
I also guess this is a very common practice for film photographers: scanning as raw as possible (a flat scan, with no sharpen) and cooking with edition software.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Pere Casals
There is no discrepancy...
You never answered the question. :)
What you describe IS a tonal adjustment.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
What you describe IS a tonal adjustment.
Yes, of course, but one thing if making tonal adjustment with scanner software and another one is doing it in Ps. I was speaking about that, as my understanding is that the thread is about that: "how to bypass all tonal adjustments" is to do it with edition.
Tonal adjustments in scanner software may work great a lot of times, but if wanting full control best is doing that in edition soft...
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Although it hasn't been mentioned from what I can see, has anyone actually done a scan with no adjustments of a stouffer wedge to see how many steps the scanner can actually read
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
I can do this later today (in my time zone).
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
I can do this later today (in my time zone).
Thanks Ken, looks forward to the results
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
IanBarber
Although it hasn't been mentioned from what I can see, has anyone actually done a scan with no adjustments of a stouffer wedge to see how many steps the scanner can actually read
Here there is an scan of a Kodak Q14 target: https://www.flickr.com/photos/timpar...125592977@N05/ , including grey scale.
This is a test made by photographer Tim Parkin. You can download a 15000 pix wide original: https://www.flickr.com/photos/timpar...532831/sizes/l
If scanning the stouffer with the Epson take care to mask the empty area to avoid any stray light, then you can make the same scan again without masking to see the impact of stray light. I would place the wedge in the long scanning direction to avoid most stray light, in this way higher densities are illuminated alone (when emply area masked).
The Tim Parkin scan shows how powerful is Velvia and how difficult is to display that greatness with present electronic displays, and shows the need of "multiexposure" feature in scanners.
IMHO Parkin is not only a great photographer, but also a master in Velvia science !
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
IanBarber
Thanks Ken, looks forward to the results
Back in 2013 (maybe earlier) I reported on this test but did not use the "flat" or "raw" methods discussed in this thread.
See http://www.largeformatphotography.in...y-for-scanning
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
Still be interesting to see the 2018 version with the flat scan
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
Ken, this is an interesting test, and anyway 3.0D is a lot for negative film.
...but I would ask if Multiexposure feature was used in that test. In my experience ME (with Silverfast) boosts max density. Also it is important how dense is the rest of the row that is scanned at the same time, if all the row is dense then we have less stray light messing in very dense spots.
My experience is consistent with what LS says: http://www.silverfast.com/highlights...posure/en.html
http://www.silverfast.com/img/highli..._ME_big_en.jpg
When scanning 135 velvia film with V850 I also noticed a difference if scanning a single strip and masking the other 3 slots in the holder. In extreme situations IMHO V850/750 have some (less stray light) advantage over 800/700 because 850/750 lenses are coated.
For most SF versions for V750/700 one has to purchase that feature separately.
Well, drums have that advantage, as a single point is iluminated then stray light dispears, the superior DR of PMT can be overcomed with ME, but stray light from the rest of the scanned row cannot be avoided.
I was thinking that perhaps flatbeds could be improved (since now have LED illuminators) with the choice of illuminating and reading smaller sections of the row, at the cost of slower scanning.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
If you want to do this properly, to see what the scanner is capable of, you need to adjust the exposure time, so that film base, of the wedge is very close to "white" or 2^16. If you want do the same for color neg, you also adjust the color gain to make the base "white" as well.
You could potentially go back then and use epsonscan, and see if you can achieve the same results, using the algorithm used by it's auto exposure.
I did this a while back with a fuji step wedge,but I can't find the file at the moment.
Two things worth remembering you should measure the results digitally, you want be able to see the differences with your eye, on a monitor. The second is that the requirements for a negative are different. It is very possible automatic setting are close to optimal in this regard.
Quote:
Originally Posted by
Pere Casals
That, link also mentions the controversial exposure time adjustment, that epson scanners DO HAVE... :D
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
That, link also mentions the controversial exposure time adjustment, that epson scanners DO HAVE... :D
IMHO there are patents involved. https://www.google.com/patents/US7102679 , this one is about noise , but perhaps other is about DR.
An scanner without "exposure time adjustment" it can also benefit from multiple exposures as averaging readings lowers noise.
IMHO a good technique is making multiple exposures with different exposure times with a single pass, this is making more than one exposure before the scanner advances to the next row. It looks that the Epsons can only make multiple exposures if making multiple passes, each pass with a different exposure time... Is this because patents ?
More expensive scanners can make multiple exposures in a single pass.
Multiple passes can be good in some cases because the super-resolution effect...
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Pere Casals
IMHO a good technique is making multiple exposures with different exposure times with a single pass, this is making more than one exposure before the scanner advances to the next row. It looks that the Epsons can only make multiple exposures if making multiple passes, each pass with a different exposure time... Is this because patents ?
Who knows for you sure, but these devices have not been advanced in a long time, where as you probably have a device in your pocket that is quite quite capable of doing what is described in that patent.
IMHO it's important not to bundle all your requirements for scanning under one banner as slides and negatives have different requirements.
Also this link has the DR results for v700 and 4990
http://www.silverfast.com/PDF/TestRe...E_DWueller.pdf
It puts it as 3.1 for a single pass. That is quite a lot when you adjust the time, to zero out the film base.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Here's a quick test of EpsonScan with no adjustments and VueScan raw with Gamma 2.2 added. There are links to TIFF files below if you're interested. Settings will be shown in another post since there's a limit to the number of images per post.
For the VueScan file I added a Gamma 2.2 layer adjustment in Photoshop. I flipped both images for easy reading. Otherwise the TIFF files are direct from the scanner. The JPGs are for quick reference. Your perception of these JPG files will depend on your monitor and its calibration.
I don't have time to perform any analysis or plotting of the values: perhaps someone would like to do that :cool:
Epson Scan with no adjustments JPG:
VueScan raw file with Gamma 2.2 adjustment JPG:
Epson Scan with no adjustments TIFF here
VueScan raw file with Gamma 2.2 adjustment TIFF here
VueScan raw file TIFF here
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Epson Scan settings:
VueScan settings:
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
And 3.4D with multiexposure it is a pretty competent job !
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quick review,
Vuescan exposure is much better, very close to perfect (what is the density of number 1 supposed to be?). From the example I assume you just used auto and slide film, vuescan does a good job in that mode.
Epson scan not so good, but it is also possible to make mistakes in the analysis, especially with Epsonscan can you post the original vuescan file, without any changes? Working from that you should be able to work out what epsonscan does.
When you did your cropping in preview for both programs, did you make sure that there was no clearer areas than step 1?
Then of course you need to it for all three colors with a filter if you want to check that aspect of it as well.:D
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
Quick review,
Vuescan exposure is much better, very close to perfect (what is the density of number 1 supposed to be?). From the example I assume you just used auto and slide film, vuescan does a good job in that mode.
Epson scan not so good, but it is also possible to make mistakes in the analysis, especially with Epsonscan can you post the original vuescan file, without any changes? Working from that you should be able to work out what epsonscan does.
Then of course you need to it for all three colors with a filter if you want to check that aspect of it as well.:D
I have added a link the original raw VueScan scan file with no gamma adjustment to the same post where I posted the others.
All those files are down-sized to a width of 1200 pixels.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Ken, just remind me why you chose Slide Film as the Media in Vuescan
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Thanks,
Will take a look and do a proper analysis over the next few, days. (my own step wedge was old and only went to 2.1)
If you have a chance to do it again, with vuescan do the preview, put a crop around step 3 or step 6 (roughly the density of BW film base). Hit preview again, the click on lock exposure, then crop the entire step wedge. (note the exposure time for reference)
Steps below your reference will be blown out, but it will be interesting to check for any improvement in SnR in darker steps.
Actually this last test is quite important, as it should show if there is any meaningful difference for BW negative scanning.
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1 Attachment(s)
Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
Here's a quick test of EpsonScan with no adjustments
Nice test !
By adjusting the curve it is made clear that the Epson reaches well 3.05D, that this wedge reaches, but with some noise in the higher, IMHO if using multiexposure noise would impreve a lot and a denser wedge would be needed to see the scanner limit.
By inspecting the values (F8, information dialog, 16 bits value) the expected value for step 4 should be 1/2 if the step 1, it goes close but with some discrepance... perhaps actual densities shpuld be checked or taken from a calibration...
Attachment 173598
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
IanBarber
Ken, just remind me why you chose Slide Film as the Media in Vuescan
I guessed that scanning it as a slide, IE a positive, would be simpler and therefore better, since no reversal step is included in the process.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
I guessed that scanning it as a slide, IE a positive, would be simpler and therefore better, since no reversal step is included in the process.
Ken, you made the best choice for the test. When using auto exposure, which is the default, unless you go looking for manual exposure. the auto exposure algorithm is different. When you choose negative it will adjust all three channels, but this is "ISO" change not a time change and actual exposure time it calculates is different. (Its shorter, probably because shorter is faster). With Raw you still get a negative regardless.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Ken, thanks for this, it is a big service to the community here.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
For the record this was a Stouffer Transmission Step Wedge sized 4x5 inches. According to the packaging it has 21 steps in "increments of .15".
If my math is correct, 21 steps amounts to a density range of 10.5 f/stops. 2 exp(10.5) = 1448, which in log (10) terms is 3.16.
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1 Attachment(s)
Re: Update to Epson scanning article: how to bypass all tonal adjustments
Most importantly if you look at those samples, yourself you see a reduction in noise, quite significant actually.
A simple method to view this is:
use a curve tool, to invert and brighten the darker steps. (adjust the intensity so yo can see the noise, I did about 75% on LAB scale)
Attachment 173601
If ken has time, and we are very lucky... he might post an example with vuescan, using an ideal typical exposure for BW negative stock. (using the method suggested earlier)
But before you rush out to rescan all your negs;), remember this will only affect highlight or brighter mid tones in a dense negative. And a lot this probably disappears under the "weight" of 4x5, but very relevant to 35mm.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
If you have a chance to do it again, with vuescan do the preview, put a crop around step 3 or step 6 (roughly the density of BW film base). Hit preview again, the click on lock exposure, then crop the entire step wedge. (note the exposure time for reference)
Steps below your reference will be blown out, but it will be interesting to check for any improvement in SnR in darker steps.
Actually this last test is quite important, as it should show if there is any meaningful difference for BW negative scanning.
VueScan based on Level 3 with Gamma 2.2 correction JPG:
Settings:
VueScan based on Level 3 with Gamma 2.2 correction TIFF here
VueScan based on Level 3 no correction TIFF here
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
before you rush out to rescan all your negs;), remember this will only affect highlight or brighter mid tones in a dense negative. And a lot this probably disappears under the "weight" of 4x5, but very relevant to 35mm.
After applying a Gamma 2.2 correction to the VueScan raw file (not adjusted to level 3, the original scan), it seems that the VueScan values are somewhat more equi-distant than the Epson values. I guess this means the VueScan scan is more linear. But what if we apply a slight correction curve to the Epson scan: will any differences become negligible ?
What does it suggest that the lowest VueScan values are shifted to the right ?
http://www.kennethleegallery.com/ima...eScanCurve.jpg http://www.kennethleegallery.com/ima...EpsonCurve.jpg
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2 Attachment(s)
Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
After applying a Gamma 2.2 correction to the VueScan raw file (not adjusted to level 3, the original scan), it seems that the VueScan values are somewhat more equi-distant than the Epson values. I guess this means the VueScan scan is more linear. But what if we apply a slight correction curve to the Epson scan: will any differences become negligible ?
You need to careful that you don't jump to the wrong conclusion. You have applied a gamma to these, so they will not be linear, and they are not. It is also probable that the gamma 2.2 function you applied does not match sRGB gamma function applied in the epson scan. What this tests shows is what the dynamic range of the scanner is, and how to make a small, and possibly imperceivable improvement.
Interesting it matches with the silverfast paper.
Quote:
Originally Posted by
Ken Lee
What does it suggest that the lowest VueScan values are shifted to the right ?
That's to be expected as you have made 2.53 X (1.2 stops) exposure increase, but this is not a tonal change as all the tonal ratio's remain the same. What you are doing is keeping the highlights away from the noise floor.
This is screen shot of the last three steps at 85%, which is a pretty extreme example, but I can see the difference in noise.
Attachment 173604
Attachment 173605
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
That's to be expected as you have made 2.3 stops exposure increase,
Why is it 2.3 stops ? steps are 1/3...
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ken Lee
After applying a Gamma 2.2 correction to the VueScan raw file (not adjusted to level 3, the original scan), it seems that the VueScan values are somewhat more equi-distant than the Epson values. I guess this means the VueScan scan is more linear. But what if we apply a slight correction curve to the Epson scan: will any differences become negligible ?
What does it suggest that the lowest VueScan values are shifted to the right ?
http://www.kennethleegallery.com/ima...eScanCurve.jpg http://www.kennethleegallery.com/ima...EpsonCurve.jpg
Should both not be in the same colourspace, either sRGB or GrayGamma 2.2 to see a better evaluation?. My understanding is that sRGB and GrayGamma are 2 different beasts.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Pere Casals
Why is it 2.3 stops ? steps are 1/3...
Careless on my part :o, Ken set the exposure time to 2.53 times increase, which I read as 2.3 the first time. I used stops out of habit.
Which I guess underscores the need to review the analysis.
2.53 X is a lot by the way, you won't be able to go that high normally. For 35mm fomapan 400 I use 2. The film has a fairly dense base. For hp5 on 120 1.2x is the max you can use. For 4x5 I measure it.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
IanBarber
Should both not be in the same colourspace, either sRGB or GrayGamma 2.2 to see a better evaluation?. My understanding is that sRGB and GrayGamma are 2 different beasts.
Its helpfull that they are in same colorspace. I converted vuescan to sRGB , and epson one to a linear scan, but could not find an easy way to post it here. Will try a bit harder tommorow.
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Re: Update to Epson scanning article: how to bypass all tonal adjustments
Quote:
Originally Posted by
Ted Baker
Careless on my part :o, Ken set the exposure time to 2.53 times increase, which I read as 2.3 the first time. I used stops out of habit.
Which I guess underscores the need to review the analysis.
2.53 X is a lot by the way, you won't be able to go that high normally. For 35mm fomapan 400 I use 2. The film has fairly dense base. For hp5 on 120 1.2x is the max you can use. For 4x5 I measure it.
Easy to fix, just replace the . by a / :), 2.3 to 2/3