an interesting question

Discussion in 'General Technical Discussion' started by Iliah, Dec 29, 2005.

  1. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    I got an e-mail from somebody who asked if he should use ProPhoto colour space in ACR exclusively. Through some correspondence it became clear that the images should be displayed on the monitor for customer to choose which should be printed in CMYK on a press.

    I tried one of the worst-case scenarios, red sunset. Using ProPhoto, it takes me about 20 minutes to get into destination monitor gamut. Using sRGB setting in ACR it is less then 2 minutes. Red was compensated with negative exposure change, all other things were done with the curve tool in ACR. In both scenarios amount of colour scattering and artifacting was about the same.

    For final CMYK we agreed on the ColorMatch RGB space, which maintains a close relation to CMYK (contrary to AdobeRGB and ProPhoto).

    So, it looks like two passes through ACR - one for monitor presentation, and a separate one for CMYK press.

    Here are 2 images I took to experiment with:

    [​IMG]

    [​IMG]
     
  2. Iliah, help, you're loosing me! I didn't understand what you meant by " getting into the destination color gamut." Why should one color space take longer than the other? Isn't this just a selection in ACR?

    How did the processing method effect the result, on the monitor, for print?

    Which was better for the sample images you posted?

    Virginia
     
  3. MontyDog

    MontyDog

    Jan 30, 2005
    #1064 - You have an error in your SQL syntax;
     
  4. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Virginia,

    ProPhoto provided gamut way too wide to be just converted to monitor colour space. That kind of conversion resulted in total loss of highly saturated reds and orange, to the point that the glimpse of the Sun on the second shot just dropped out of sight :) After converting through ACR to ProPhoto extensive file editing was needed to preserve reds, but to compress them into sRGB gamut. Many moves I tried were quite damaging.

    When sRGB was set in ACR as destination space all I needed to do was to use ACR tools to bring the scene back to what I saw in reality. It was much simpler and faster. No need to switch gamut warning on, convert to Lab, play with channel curves, desaturate, darken,.....

    The best RGB space to work in is the one that is the destination space, or bear close relationship to destination space.
     
  5. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    What can I say Paul :) Just to add that compressing gamut I needed somehow to maintain the sensation of the original scene.
     
  6. Thank you, Iliah. I am often overwhelmed by your "tidbits of light."

    What would be useful for me is a general method for processing my images that can serve multiple purposes.

    My methods have changed a little now that I've started to use LAB processing. I begin with the RAW camera file and bring it into PSCS2 in the ProPhoto color space. Once in PSCS2 I change the color space to LAB and use the a, b and lighten curves, lightening levels and shadows adjustment as needed.

    Then I convert my image to 8-bits and save as an SRGB PSD master. I also sharpening and use noise reduction on my SRGB PSD master, somethimes in different layers. I use SRGB to save, at this step, because most of the time I am using images for the web.

    When I want to print, I use my SRGB master PSD and simply convert a duplicate of that image flattened to the printer's color space.

    Comments and suggestions appreciated.

    Thanks,

    Virginia
    aka beaucamera
     
  7. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Virginia,

    Why not to keep "master" in Lab, and not to do sharpening and noise reduction in Lab as well?
     
  8. Iliah, the sharpening works fine in LAB and sometimes I do that in 16-bit, but Noise Ninja, my noise reduction tool, does not work in the LAB color space.

    Is sharpening better done in 16-bit?

    Thanks,
    Virginia
     
  9. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Virginia,

    Sharpening operations run better in low gamma space (Lab is gamma = 1 space basically); 8 or 16-bit depends on the gamut. For Lab I can't see difference in prints; ProPhoto and like command for 16-bit operations.

    You can trick NN into Lab mode, that will need copying channels from Lab document into grayscale document; and pasting them back after processing.
     
  10. Thanks for the tip, Iliah. Apparently you can run Noise Ninja on 16-bit LAB channels. Anybody else done any experimenting with this?

    Virginia
    aka beaucamera
     
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