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Thread: Epson Scan: What is 'Color Control' doing exactly?

  1. #1

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    Epson Scan: What is 'Color Control' doing exactly?

    Hello everyone,

    For my family archiving project, I am scanning many thousands of printed photos. Ideally, I would like to take an unmanipulated scan of each photo, with any aesthetic changes to be made in Photoshop on an ad hoc basis. I'd also prefer to do this using TIFF, and without resorting to DNG and third party tools like VueScan. I have therefore been experimenting with using Epson Scan with the 'no color correction' mode enabled.

    My problem, unfortunately, is that I can't replicate the 'look' achieved by Epson Scan's automatic color control function in Photoshop. I'm therefore keen to establish precisely how Epson Scan's color control function manipulates images, such that I can try to replicate it in Photoshop.

    Certainly, Color Control seems to apply an exposure/gamma adjustment, but it also seems to toy with the color levels in unclear ways. Even when I manually revert histogram, tone and palette adjustments to zero (in theory, leaving only the gamma difference), the end result is a photo that looks more vivid and colorful than the 'no color correction' equivalent -- even when exposure/gamma is matched.

    If all adjustments are zeroed, then just what is it adjusting behind the scenes? Is 'no color correction' actually using a different non-Epson RGB profile altogether?

    I would be grateful for any information members of the forum could offer.

  2. #2
    Alan Klein's Avatar
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    Re: Epson Scan: What is 'Color Control' doing exactly?

    I don't know if this will help. But when I first got my Epson V600 ten years ago and scanned color film, I found I could get the same color corrections by scanning with No Color Correction and then using Auto Levels in Photoshop Elements on the "flat" image file. Levels have to do with black and white points. However, I cannot seem to duplicate the ease that Elements does it when I try to do it with Lightroom. I don't have regular Photoshop so I can't comment on its editing. Of course, none of this may help with prints, but who knows?

  3. #3

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    Re: Epson Scan: What is 'Color Control' doing exactly?

    Many thanks for your reply, Alan.

    I just had another go with auto levels in Photoshop. Unfortunately, it over-exposed the image far beyond what Epson Scan's Color Control produced. I've tried a few types of auto level -- such as monochromatic focus, contrast focus, etc -- but the result never seems to tackle the issue of muted color. There seems to be something in Epson's Color Control feature which adjusts colors 'under the hood', even when I specify no level adjustments. I'd love to know what it's doing, if only so I can copy it

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    Alan Klein's Avatar
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    Re: Epson Scan: What is 'Color Control' doing exactly?

    My underwater Ektachrome slides were drab due to the absorption of color due to being underwater. What surprised me was when I used Color Control with my V600. It brought back the colors greater than I recall them being in the original slide of 30 years ago.

    There are some variables even with Auto Color Control that you can change in Epsonscan. Have you checked the manual? Which manual do you have? There are different ones that have more or less instructions than the other. What scanner are you using?

    Also, click on Configuration at the bottom that takes you to another page where there are some other adjustments. Maybe you can limit some of these for the scan yet leave enough room for additional adjustments in post.

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    Re: Epson Scan: What is 'Color Control' doing exactly?

    I have the V500. I have set everything at zero in the various settings, such that the histogram is full (0-255, 1.0 gamma) for all colours, no further tweaks, no auto exposure, no unsharp mask, etc.

    As best I can tell, I am comparing two scans which should be identical except for one having 'Color Control' enabled in the configuration settings. It's not clear to me what changes this Color Control makes behind the scenes: Is it adjusting colors above and beyond what are manually set? Certainly it is adjusting exposure, even though auto exposure is manually turned off. Is it adopting a different color profile compared with 'no color correction' (e.g. SRGB vs. Epson RGB)?

    I've had a look at various Epson manuals from my model on up, but none offer any detail on what's being done by the software. It's something of a black box -- unfortunately, it's a rather effective black box, and I'd love to know how to produce the same effect in a reliable manner using Photoshop or other post-scan tools.

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    Re: Epson Scan: What is 'Color Control' doing exactly?

    Quote Originally Posted by Alan Klein View Post
    ...
    Alan, by chance, I stumbled across a post of yours on another forum where you seek an answer to yet another question I've been pondering!

    https://www.photrio.com/forum/thread...sitive.151354/

    Just based on the way Epson Scan applies changes to the preview 'on the fly', it's not clear to me that the curve it applies affects the scan or quantisation of data from the scan. Epson Scan's behaviour seems more consistent with something that is done after the data has been generated and quantised, which would mean there is no particular reason to use its level tools over those of Photoshop.

    Did you ever get a convincing answer to this question?

    I have tried asking the same question on someone's blog (see below). I think we were getting at the same thing?

    In my tinkering with Epson Scan and Photoshop, I have been unable to establish that the curve tool affects either (i) the speed/mechanism of the scan (e.g. exposure time), or (ii) the manner in which that stream is quantised within a color space.

    If either were the case, it would make sense to apply the curve within Epson Scan. This is so, respectively: (i) the hardware can expose/slow the scan for optimal results, or (ii) so that non-integer levels are quantised optimally, reducing blotchy areas. If neither of these things is taking place, then the Epson Scan curve is equivalent to applying an effect in Photoshop after the fact, once the data for each pixel is already set in stone.

    Do you have any resources which document if/how Epson Scan affects the scan or quantisation? It would be good to have a clear sense of what's happening under the lid before I embark on a big scanning project.

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    Alan Klein's Avatar
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    Re: Epson Scan: What is 'Color Control' doing exactly?

    My belief hasn't changed in ten years of scanning with the V600 and V850. Scans are static. All changes made by Epsonscan and the other scan programs are made after the scan not before or during. You can actually see this on a pre scan.

    First do a prescan. Then go to configuration and turn auto color control on and off. You will see that the display of the prescan results go from flat with no edits to proper color exposure when you switch to auto color control. Since the scanner is not scanning again but using the same scanned results, it obviously supplying those changes to the already scanned image file. That's exactly what happens on the final scan. You can also apply manual changes to the prescan.

    The only difference in the final scan is the scan slows down to collect higher resolution and bits, But the edits are done after the scan is completed. So there's really no reason to learn another editing program in the san software. Just use it to scan "flat" and apply all the edits afterwards in you favorite post processing software.

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    Re: Epson Scan: What is 'Color Control' doing exactly?

    Thanks Alan, that definitely matches my experiences with the software.

    Edit: In doing some googling, I've come across this page which you might be interested in. I'm not sure it affects me directly (as I'm scanning prints), but the author found that adjusting the histogram for negative scans varied the scan time substantially -- from 1.5 mins to around 5 mins. This suggests that the scanner may be adjusting the exposure time for negatives at a physical level, and not just as an after effect achieved in software. I would be interested to hear if you've had similar experiences. I've tested it with prints and found the scan time didn't change, but have yet to have a go with negatives.

    Also, seeing as you and I seem to have a similar approach to these things, can I ask one final question?

    When you take your initial scan, do you move the input/output levels in the histogram to 0 and 255? My thinking here is that this captures all colour information the scanner is capable of resolving without any tweaking post-scan. However, Epson Scan seems rather insistent on narrowing the range by default, I think to something like 10 and 245. I figure this is because pure whites and blacks can cause trouble with some printers, e.g. by not depositing any ink in areas with pure whites, which would produce a strange variance in gloss across the photo paper. Perhaps Epson is just trying to idiot-proof the process?

    Thanks again for your help, Alan.
    Last edited by Ninny148; 14-Mar-2021 at 07:52.

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    Alan Klein's Avatar
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    Re: Epson Scan: What is 'Color Control' doing exactly?

    Quote Originally Posted by Ninny148 View Post
    Thanks Alan, that definitely matches my experiences with the software.

    Edit: In doing some googling, I've come across this page which you might be interested in. I'm not sure it affects me directly (as I'm scanning prints), but the author found that adjusting the histogram for negative scans varied the scan time substantially -- from 1.5 mins to around 5 mins. This suggests that the scanner may be adjusting the exposure time for negatives at a physical level, and not just as an after effect achieved in software. I would be interested to hear if you've had similar experiences. I've tested it with prints and found the scan time didn't change, but have yet to have a go with negatives.

    Also, seeing as you and I seem to have a similar approach to these things, can I ask one final question?

    When you take your initial scan, do you move the input/output levels in the histogram to 0 and 255? My thinking here is that this captures all colour information the scanner is capable of resolving without any tweaking post-scan. However, Epson Scan seems rather insistent on narrowing the range by default, I think to something like 10 and 245. I figure this is because pure whites and blacks can cause trouble with some printers, e.g. by not depositing any ink in areas with pure whites, which would produce a strange variance in gloss across the photo paper. Perhaps Epson is just trying to idiot-proof the process?

    Thanks again for your help, Alan.
    I've never seen a difference in scan time with the Epson V600 or V850 by changing the histogram settings. Using ICE doubles the scan time. Changing the resolution changes it too, I believe. But I always use 2400.

    I sometimes set the histogram to the edges of where the image shows. So for example, if the image shows 15 to 200, I'll set it at 10 to 215. People have claimed you get more data that way but I have;t been able to confirm that. It may be the same results as scanning flat 0-255 (in and out) and adjusting the levels (black and white points) in post. I've done it that way too and frankly, can't see the difference. Either way, I do final tweaking in post-processing.

    I don;t use the auto setting because for some reason it seem to set it less than the picture's histogram range.

  10. #10
    Corran's Avatar
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    Re: Epson Scan: What is 'Color Control' doing exactly?

    Quote Originally Posted by Ninny148 View Post
    I just had another go with auto levels in Photoshop. Unfortunately, it over-exposed the image
    You can set the limit on clipping the edge of the histogram for auto adjustment in Photoshop. Try 250 or thereabouts instead of the default.
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