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Thread: Update to Epson scanning article: how to bypass all tonal adjustments

  1. #11

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by IanBarber View Post
    Ken, In VueScan, doesn't Crop Buffer % value determine how VueScan adjusts the brightness
    Even if you set it to 0, the brightness of the image changes as you vary the cropping.

  2. #12

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by Leigh View Post
    Why not use EpsonScan rather than VueScan.

    EpsonScan came with my V750. I'm sure it also came with your V700.

    For a plain-vanilla scan, you don't need any of the fancy VueScan features, so why use it?

    - Leigh
    Yes, that's one of the points made in the article: I don't use VueScan. It's a rather long article, so that may have escaped people's attention if they only had time to skim it, or skim this thread for that matter.

    I have simply added some information to the article, for those people who have asked me how to make a plain scan with no adjustments whatsoever.

  3. #13

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by Ken Lee View Post
    Even if you set it to 0, the brightness of the image changes as you vary the cropping.
    I will do some testing with this tomorrow especially with the crop buffer and report back my findings

  4. #14

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by IanBarber View Post
    How does the Epson Scan deal with Gamma with these settings. Does it still encode in gamma 2.2 or is there a way to force it to give a true Linear scan with a Gamma of 1.0
    When you scan in epson scan with the gamma set to 1.0, the file you output will be encoded into the sRGB gamma (most likely 100% correctly) unless you say differently I think you can also use adobeRGB which has similar gamma. You can convert it easily enough to 1.0, a couple of different ways, and you should get exactly the same thing, before epson scan applies the correction. ColorPerfect I understand offers this feature. You only need a gamma of 1.0 if you intend to do your own image processing, in which case you can convert it yourself as long as you know the original gamma. When you use tools like LR they will automatically convert it a gamma of 1.0 internally to store in its own working space.

  5. #15

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by Ken Lee View Post
    Vuescan automatically adjusts image brightness as we crop.
    What your probably seeing there is vuescan simulating the exposure change, that it intends to make when you actually do the scan. Vuescan actually allows you manual control this, and I think it also allows you do this for each color channel. It certainly allows the adjustment of the later. Just like changing the shutter speed, changing the exposure time of the CCD is not a tonal change.

    There is no manual control of this in epson scan, though presumably it makes use of this feature, most probably it has calculated it before you are presented with the preview.

  6. #16

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    When you scan in epson scan with the gamma set to 1.0, the file you output will be encoded into the sRGB gamma (most likely 100% correctly) unless you say differently I think you can also use adobeRGB which has similar gamma.
    Ted, are you saying that even if you choose gamma 1.0 in Epson Scan, it will converting along the way to gamma 2.2 which is what (sRGB or AdobeRGB 1998) are

  7. #17

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by IanBarber View Post
    Ted, are you saying that even if you choose gamma 1.0 in Epson Scan, it will converting along the way to gamma 2.2 which is what (sRGB or AdobeRGB 1998) are
    Yes, otherwise you would not be a happy photographer BTW sRGB is not exactly 2.2 but close enough, same for adobeRGB.

    In addition I assume we are talking about scanning positives, because scanning a negative is different.

  8. #18

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by Ted Baker View Post
    Yes, otherwise you would not be a happy photographer BTW sRGB is not exactly 2.2 but close enough, same for adobeRGB.

    In addition I assume we are talking about scanning positives, because scanning a negative is different.
    I was referring to scanning black and white negatives

  9. #19

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by IanBarber View Post
    I was referring to scanning black and white negatives
    In that case the gamma etc, still applies. But the method of inversion is potentially unique to each program, it may not be a big secret, the point being no vendor that I am aware of publishes it. For example what is the method used by epson? How this is done most certainly effects the tonal relationship, this is most obvious in colour photography, but it also applies in BW.

    If you do a raw scan (Vuescan/Silverfast/DSLR raw file), a negative will come out looking like a negative, with no gamma applied. If you use epson scan you can scan a negative as a positive, and remove the sRGB gamma later. I believe colorperfect supports the later.

    If you stay in 16bit integer, you can potentially unravel any tonal changes, exactly if you know what the original changes were (assuming you round up/down correctly). Clipping is the exception of course, but that is not a tonal change. If you use a RGB curve tool in software later down the line you can also unravel those changes, (or indeed make your own), and get back to the original potentially. I hope this makes some sense.
    Last edited by Ted Baker; 7-Jan-2018 at 05:03.

  10. #20

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    Re: Update to Epson scanning article: how to bypass all tonal adjustments

    Quote Originally Posted by Ted Baker View Post
    What your probably seeing there is vuescan simulating the exposure change, that it intends to make when you actually do the scan. Vuescan actually allows you manual control this, and I think it also allows you do this for each color channel. It certainly allows the adjustment of the later. Just like changing the shutter speed, changing the exposure time of the CCD is not a tonal change.

    There is no manual control of this in Epson scan, though presumably it makes use of this feature, most probably it has calculated it before you are presented with the preview.
    I think I finally grasp what you are saying. Duhhh

    I made a scan with VueScan and configured it to output both a raw file and a tiff file. The tonal scale of the tiff file was affected by cropping and adjustments made in the Color tab like curve low, curve high. In addition, a gamma adjustment of approximately 2.2 has been applied to the tiff file. The resulting tiff file matches what we see in the preview pane.

    The raw file, on the other hand, looks rather dark, because not even a gamma correction has been applied. It's just the original scanner acquisition of the image.



    If we apply a gamma correction to the raw file, it begins to resemble the TIFF image (which may also contain tweaks from the Color tab and cropping).



    Finally, the Epson scan, Apple Image Capture and Windows Scan drivers are all silently applying a gamma correction to the scan. Turning off all corrections in the Epson drivers, we get an image which matches Apple Image Capture and Windows Scan, but none of these 3 approaches actually delivers the original scanner capture because a gamma adjustment has been applied in all 3 cases. In fact, the only configuration which delivers the original scanner capture, is the VueScan raw file.

    ...Is this correct ?
    Last edited by Ken Lee; 7-Jan-2018 at 08:29.

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