Confused With ColorPerfect Input

Discussion in 'Digital Darkroom' started by dmitry_shijan, Dec 8, 2012.

  1. Hello. I like the idea of RAW scanning but i still can't understand how the ColorPerfect works and how to organize correct workflow without color data loss. My aim is to output more-less correct images with ProPhto RGB color space for further adjusting in Camera RAW or Lightroom
    Let's suppose that i have scanned color negative in Vuescan to image with linear gamma and without color profile in it (as described in ColorPerfect FAQ). Before process it in ColorPerfect i need to open image in photoshop. When i open image in photoshop i see a dialog box which purpose me to leave image without profile or assign profile. And here begins mystery. As i know it is not correct just assign profile to untagged image, but in ColorPerfect plugin FAQ it is told that i just need to assign profile to image (just assign, not convert) before or after processing. OK i left image untagged and assign ProPhto RGB to it after processing and have madness saturated colors as i expected of just assigning profile.
    Correct me if i wrong but image needs some starting coordinates for RGB values, sone starting scanner color space to begin work with or convert color coordinates to another space, and it is wrong to put untagged image in photoshop or ColorPerfect which have no idea how to understand those image.
    So my general question is to those who uses ColorPerfect - how should i open image in photoshop before process it in, and how should all workflow looks like to have image in ProPhto RGB color space?
     
  2. And few more thoughts about this.
    I got Epson V10 scanner it's bundled software makes very good results and colors are visually identical to original image. There are also two input profiles for that scanner installed with it's driver (Perfection V100 film and Perfection V100 ref). Those profiles have no extension and if i open them in ColorSync they seen as Class: Input. The profiles have pretty wide color space and bizzare shape (see picture below).
    So i made a little test:
    First scan made with Epson Scan utility to sRGB.
    Second scan made with Vuescan RAW to Tiff with linear gamma
    Then i open those files in Photoshop, leave linear scan untagged and try to adjust gamma to match sRGB scan from Epson Scan, but the colors were very different. Then i try to assign those Perfection V100 ref profile (by the way it was seen in photoshop's profiles list) and in this way after adjusting gamma exactly to number 1.8 (don't know why it appear to be 1.8) the colors and overall look became perfectly match to the sRGB scan internally processed by Epson Software.
    This all means that image scanned even with linear gamma needs correct input profile from capture device to be correctly seen by application! And even averaged device profile works pretty well here. That's why i'm so worry about those mismatch in ColorPerfect workflow.
     
  3. Then i open those files in Photoshop, leave linear scan untagged​
    That's one reason it looks so awful, it's untaggged and assumed to be in a color space based on your color settings. Since it isn't close to any of those options, it looks pretty bad. IF you assign the actual profile that defines this linear data, it would not look bad at all. Now the question becomes, what's so useful about a linear scan when you'll probably want to convert to a well behaved RGB working space where R=G=B is neutral (not necessarily the case with the linear so called "raw" scan.
    This all means that image scanned even with linear gamma needs correct input profile from capture device to be correctly seen by application!​
    Exactly correct. Does the scanner provide this? If not, then the workflow of scanning linear is even more half baked IMHO.

    There's a reason why we work with gamma corrected images. Now if we were discussing a DLSR who's sensor has to hand off linear encoded data at some point (but could be converted to a working space), that's a different story. Even more important than the gamma encoding in an editing space is whether or not it's well behaved where you can be assured that three equal values or RGB are indeed neutral. That may not be the case with a scanner profiled linear or otherwise.
     
  4. Here is another research:
    Same scanned RAW Tiff from Vuescan with linear gamma without profile was opened in ColorThink application (same as Andrew Rodney done in its video tutorial) and what i see - visually it fits to sRGB space. Ok, i thought that maybe its not enough saturation there and open image in Photoshop without assigning profile, boost saturation to the limit, save it without profile, then open again in ColorThink and again see the image ideally fitted to sRGB space.[​IMG]
    This probably means that any other app will work with those unassigned linear image in sRGB space (same as browser or any OS do by default with unassigned images from internet). And files processed in ColorPerfect became sRGB from the moment when they are opened in Photoshop, so bye bye wide gamut...
    I also open uncorrected image from Epson Scan with assigned Perfection V100 ref profile and as i expected i see its huge native gamut there.[​IMG]
    Also i noticed that RAW images from Vuescan cannot be opened in NikonScan software (madness but it just don't see it as supported file type in browser), same time NikonScan can open, edit and convert any other usual images.
    Seems there is really something unknown in those RAW linear images from scanner apps. Maybe there is some kind of additional low level data in them which is san be read correctly only by apps which create those files? Any thoughts or ideas about this?
    And some thoughts about Nikon:
    Nikon Scan install its input profiles for all scanner models but they are encoded and Photoshop can't see them it profile list. Those profiles have Class: 'nkpf' i hear thai its some kind of proprietary nikon profile type. How do you think is it possible to decode those profiles for use them with RAW scanner files? Also maybe someone can share its custom build profiles for Nikon scanner?
     
  5. And files processed in ColorPerfect became sRGB from the moment when they are opened in Photoshop, so bye bye wide gamut...​

    That's lousy! The scanner isn't anything like sRGB.
     
  6. I believe that all original wide space data still there but without input profile it temporary assigned by photoshop and other apps to sRGB. And without input profile there is no chance to see those data in other way.
     
  7. Oh so you assigned sRGB to the data shown in ColorThink?
     
  8. no. i'm not assign sRGB to it. seems you read inattention or i wrote too complexity :)
    i put to ColorThink image scanned with linear gamma without any profile at all. (so called RAW image scanned with Vusecan). And ColorThink seen it as sRGB.
     
  9. i put to ColorThink image scanned with linear gamma without any profile at all​
    ColorThink needs an embedded profile to plot the gamut. You must have assigned it there, hence it shows you the colors within sRGB. You need to tag the linear scanner behavior to this data, then plot the gamut. Without an embedded (assigned) or assumed color space, the numbers have no scale to plot a gamut.
     
  10. Sure, any app needs an embedded profile. I do it for test to figure how actually applications see images without embedded profile.
    But the main practical question after all this - where to find Nikon Scanner input profiles in nonproprietary nikon profile type?
     
  11. And finally here it is! Beautiful native Nikon input profile:
    [​IMG]
    Download here http://cl.ly/LTFq
     
  12. unfortunately my concept became wrong and seems nikon native profile is more complicated than i thought. i don't find a way to assign correctly those profiles in photoshop, as so as image from Nikon behaves same as usual sRGB image when i assign profile to it.
    in Nikon manual i find info about Wide Gamut RGB (compensated)
    "because the gamut has been expanded in a non- linear fashion to incorporate just those colors that could not otherwise be expressed, it can not be represented in chro- maticity diagrams using a standard RGB triangle"
    now i think that Scanner RGB profile is build with same technology and the problem is that it just can't be represented.
     
  13. And seems i finally find a correct way to open files in ColorPerfect. Few days ago i done a custom ICC profiles for scanner and now my workflow looks like:
    1. Scan to negative with linear gamma
    2. Open in Photoshop and assign custom ICC input scanner profile with linear gamma
    3. Convert to profile with Gamma 2.2 (currently i choose Best RGB)
    4. Open ColorPerfect plugin
    5. Choose gamma only (choose 2.2 or other number, depending of visual preference)
    6. Adjust black and white points to avoid clipping
    7. Adjust WB (if needed)
    8. Do other adjustments in Photoshop
    PLEASE NOTE that "Beautiful native Nikon input profile" posted above DON't WORKS in this way. You need to made your own profile with IT 8.7 target, or find somewhere exposure independent profile, generated with VueScan on same model of film scanner as yours.
     
  14. And workflow in post above became wrong too. After few letters to ColorPerfect developer i come to this:
    1. Take your scanner input ICC profile (bundled with software or build with IT8 target) and than in Photoshop make a simplified ICC profile with Gamma 2.2 and white point 5000 based on this input profile.
    2. Open scanned image in Photoshop and assign (DO NOT CONVERT) those ICC profile. As for me It work better than assign AdobeRGB which is not fits very well to scanned image.
    3. Open ColorPerfect plugin, choose input gamma - L and gamma C only - 2.2
    4. Do most that you can in ColorPerfect, but not in Photoshop.
    5. Do slightly other adjustments in Photoshop, some tiny Brightness/Contrast for example.
     
  15. And workflow in post above became wrong too. After few letters to ColorPerfect developer i come to this:
    1. Take your scanner input ICC profile (bundled with software or build with IT8 target) and than in Photoshop make a simplified ICC profile with Gamma 2.2 and white point 5000 based on this input profile.
    2. Open scanned image in Photoshop and assign (DO NOT CONVERT) those ICC profile. As for me It work better than assign AdobeRGB which is not fits very well to scanned image.
    3. Open ColorPerfect plugin, choose input gamma - L and gamma C only - 2.2
    4. Do most that you can in ColorPerfect, but not in Photoshop.
    5. Do slightly other adjustments in Photoshop, some tiny Brightness/Contrast for example.
     

Share This Page