ColorNeg (erstwhile NegPos) and color spaces

Discussion in 'Digital Darkroom' started by arnabdas, Mar 1, 2010.

  1. When scanning slides I scan into a linear tiff and then assign my scanner's color space (for linear tiffs) in photoshop. Then I do a perceptual conversion to ProphoRGB.
    However, negatives are a different story and I found out I get satisfactory results only by using CF Systems ColorNeg. I purchased a registration key last night.
    However, I don't completely understand how ColorNeg handles color spaces and profiles.
    The input file is 16-bit linear tiff without a color profile, as asked. But after conversion -- what is the recommended approach for assigning/converting to ProphotRGB?
    Is there any setting buried somewhere in the UI that let's me choose the output color space?
  2. It's only a plugin and does not do colour management on that level. It's still just a PS document for your purpose.
  3. So does it mean I can just assign the ProphotoRGB color space after it has pulled up the gamma?
  4. digitaldog

    digitaldog Andrew Rodney

    There hasn’t been a real solution for profiling for color negs since day one. The exposure effect on the orange mask and a number of other issues make it nearly impossible to build a profile as you can for transparency. So various scanner drivers come up with their own internal method of encoding the data which is what you should stick with. I don’t know what scanner driver you’re using. LaserSoft does an excellent job and would allow you to encode into any RGB working space it supports, including ProPhoto RGB.
  5. Arnab: I would convert, not assign. But the answer is yes.
    Andrew: I have *never* seen a scan program perform that task to my liking. I prefer the linier raw scan to ColorNeg/Pos approach. It lets each software be the best at what they do well. As for Lasersoft, I don't care for their approach.
  6. "Arnab: I would convert, not assign. But the answer is yes." Peter C
    Peter, I just noticed ColorNeg automatically converts (or maybe just "assigns") the currently active working color space. In other words, if I have ProphotoRGB working space, after OK'ing out of the Colorneg filter dialog I see the image has the ProphotoRGB profile attached.

    Question is -- that the recommended workflow?
    I think the key question here is which profile best interprets the color numbers that ColorNeg comes up with after pulling up the gamma and other adjustments?
  7. I don't think it really matters. I never noticed what it would be before I ran the plugin, as I always convert it before I save (I do the rest of my edits in LR),
  8. In the meantime, I have had a couple of email exchanges on this with David Dunthorn, author of ColorNeg.
    Looks like the workflow I am following is alright but I had missed one key piece which he pointed out -- setting the "Gamma C" value for the target color space. In my case for ProphotoRGB (which has a gamma of 1.8) -- the Gamma C had to be changed from 2.2 to 1.8.
    Hope this helps.
  9. Yeah, I have a complete 1.8 calibrated environment. I do mostly QTR printing and that's what it uses. I set it a while back, and it keeps that setting for everything I do.

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