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Thread: Scanner comparisson page and drum scan limits?

  1. #41
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    Re: Scanner comparisson page and drum scan limits?

    Unfortunately, the printer and the paper/ink combination have a limited gamut, but before we squeeze the final image into that limited gamut, it's best if our tools distort the color space as little as possible, all along the way.

    Not distorting, translates to retaining as many steps as possible.

    Nobody is claiming that we can see or manage all those subtle steps.

    We just want to retain as many as possible, so that things remain as "analog" as possible, as long as possible.

  2. #42

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    Re: Scanner comparisson page and drum scan limits?

    Attached is a step wedge chart in 8 bit. Perhaps my eyes just suck, but if there is a huge difference between 2 adjacent tones (1 full step apart), then it is not apparent to me on my monitor or on paper. I'll provide the full res .psd file if anyone wants it.
    Attached Thumbnails Attached Thumbnails Step Wedge.jpg  

  3. #43
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    Re: Scanner comparisson page and drum scan limits?

    The problem isn't when we view a complete 256-step wedge.

    The problem is when we start out with a small color space, and proceed to make lossful adjustments. This introduces gaps, or banding. With further adjustments, banding become increasingly apparent.

    256 tones is nice to finish with (and that's all we can ever get in the end, because printer dirvers are only 8-bit), but if we start out with only 256, the number of steps can only decrease as we perform adjustments.

    On the other hand, if we start with 64 thousand tones per channel, we could lose 1000 steps and they wouldn't likely be noticed. If we start with 256, it doesn't take many losses to become apparent. It's a familiar look when (8-bit) JPG files are overly "corrected" by amateur digital photographers. That's why higher end cameras allow Raw capture, and modern imaging software supports it. Google 16 bit Workflow to learn more.

    Performing adjustments in a large color space, prevents banding. That's why we convert to the smallest color space, last - just as we do with sharpening.


  4. #44

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    Re: Scanner comparisson page and drum scan limits?

    Quote Originally Posted by Ken Lee View Post
    The problem isn't when we view a complete 256-step wedge.

    The problem is when we start out with a small color space, and proceed to make lossful adjustments. This introduces gaps, or banding. With further adjustments, banding become increasingly apparent.

    256 tones is nice to finish with (and that's all we can ever get in the end, because printer dirvers are only 8-bit), but if we start out with only 256, the number of steps can only decrease as we perform adjustments.

    On the other hand, if we start with 64 thousand tones per channel, we could lose 1000 steps and they wouldn't likely be noticed. If we start with 256, it doesn't take many losses to become apparent. It's a familiar look when (8-bit) JPG files are overly "corrected" by amateur digital photographers. That's why higher end cameras allow Raw capture, and modern imaging software supports it. Google 16 bit Workflow to learn more.

    Performing adjustments in a large color space, prevents banding. That's why we convert to the smallest color space, last - just as we do with sharpening.

    Starting with 256 discrete tones, but working in 16 bit will not introduce many, if any, banding issues. I'm quite familiar with 16 bit.

    Working in a large color space, such as Prophoto RGB, will encourage more banding, because the tonal neighbors must be spaced further apart than with a small color space (both color spaces will have the same total number of discrete tones) - your gamut is wider but the tones must be spaced wider as well. If you are working with a low gamut image (such as a foggy scene), you are better off working in a small color space, such as Adobe sRGB, because the tonal values will be closer together and have a lower probability of banding.

  5. #45
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    Re: Scanner comparisson page and drum scan limits?

    Quote Originally Posted by Ken Lee View Post
    <snip>
    Performing adjustments in a large color space, prevents banding. That's why we convert to the smallest color space, last - just as we do with sharpening.

    Is that right? If we have a 16 bist per channel RGB image, aren't the number of colors/shades equal no matter whether we use sRGB or ProPhoto? Isn't what happens is that the number of steps are the same, but there's bigger jumps between the steps in ProPhoto, since the same number of steps has to cover a bigger area, as it were. If so, then aren't you more likely to see banding with the larger color space? I'm sorry if I have this wrong, as I'm no color space expert.

    Oops. I see that Greg types faster than I do.
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  6. #46

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    Re: Scanner comparisson page and drum scan limits?

    [QUOTE=Ken Lee;626685]Performing adjustments in a large color space, prevents banding. That's why we convert to the smallest color space, last - just as we do with sharpening.

    This is not correct (see my previous post). Working in a larger color spaces encourages banding. Working in higher bit depth discourages banding.

  7. #47
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    Re: Scanner comparisson page and drum scan limits?

    Yes, I stand corrected. I meant bit-depth. Not color space.

    My post should have read as follows

    ...Performing adjustments in higher bit-depth, prevents banding. That's why we convert to the smallest bit depth, last - just as we do with sharpening.

  8. #48

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    Re: Scanner comparisson page and drum scan limits?

    And my conment was directed to the other comments about "124, up to 125 too sledge-hammerish". You have to look pretty carefully to detect the difference in 1 step on a step wedge. In a "real" photo, and without a direct A to B comparison, it would be pretty darned difficult for a human to reliably identify that a few pixels ended up 1 value off and had a few neighbor pixels with the same value. If an entire section of pixels all ended up with the same value that would be different, but I think it would be pretty rare for that to happen.

  9. #49

    Re: Scanner comparisson page and drum scan limits?

    Quote Originally Posted by Lenny Eiger View Post
    Guys, before you jump all over everyone-- there is some serious compression of tones that happens on occasion, at least. I'm not sure where exactly it occurs. I assume its in Photoshop, but it could be in the rip. There's a certain effect that I get when I use an 8x10 piece of film that adds an extreme amount of textural quality. I think it should be able to happen at smaller formats, certainly 4x5, given resolution of lenses, excellent film and developers, the best kinds of scanners, etc. All the stuff we all use.

    I realize the eyes can only go so far, monitors only os far, etc. I continue to struggle to get more than I am getting from smaller film...

    This doesn't have to do with world views...

    Lenny
    Lenny, two givens-

    1) "some serious compression of tones... ...happens on occasion"
    2) the Photoshop curves tool has control points in increments of 256, both
    in and out, no matter the number of levels in the
    file.

    One has little, if anything, to do with the other.

    another two-
    1) world views
    2) facts

    Again, one has little, if anything, to do with the other.

    As a note of interest perhaps, your multi K setups will indeed
    differentiate between more than 256 levels of gray (given enough room on
    the paper), unfortunately StudioPrint converts to 8 bit on the fly behind
    your back, before continuing on with the magic it does. Don't ask me to
    write the novel required to explain how I arrived at that. So, there is
    one bottleneck, though I don't think the problem you mention is at that
    point. Still, I'm in agreement that there should be no downscaling of
    levels of gray anywhere in the data path if at all possible, but PS tools are a different issue.

    Peter, I had no idea you were referring to LAB, that's an entirely
    different can of worms, and you are right about the increments of control
    points available with it in PS.
    At risk of offending you as you may be well aware already, there are other
    perhaps more useful tools. Despite it's silly Tron like interface, i1
    Share (free) will let you measure in accurate LAB values and tell you the
    equivalent RGB value in any selected working space, for example.
    Tyler

  10. #50

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    Re: Scanner comparisson page and drum scan limits?

    Quote Originally Posted by Tyler Boley View Post
    Lenny, two givens-

    1) "some serious compression of tones... ...happens on occasion"
    2) the Photoshop curves tool has control points in increments of 256, both
    in and out, no matter the number of levels in the
    file.

    As a note of interest perhaps, your multi K setups will indeed
    differentiate between more than 256 levels of gray (given enough room on
    the paper), unfortunately StudioPrint converts to 8 bit on the fly behind
    your back, before continuing on with the magic it does. Don't ask me to
    write the novel required to explain how I arrived at that. So, there is
    one bottleneck, though I don't think the problem you mention is at that
    point. Still, I'm in agreement that there should be no downscaling of
    levels of gray anywhere in the data path if at all possible, but PS tools are a different issue.

    Tyler


    There's part of this that is just interim, or incomplete thinking. I've been working for a long time to get to a fully textured appearance. I have been successful at getting there with an 8x10 camera. However, I believe I should be able to get there with a smaller piece of film - at least one as large as 4x5. Somehow it doesn't work that way - at least not yet. There's a smoothness I haven't gotten to. I'm grasping at straws to figure out where the bottleneck is. I have very smooth gray ramps in my environments but the magic is only there with the big camera - at least so far. More testing to come.

    I do know that StudioPrint is 8 bit. They just told me, thankfully no novel needed.

    My statement about world views had to do with the comment you made about "losing touch with these discussions every day..." It was an attempt at levity.

    Lenny

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