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Author Topic: Color Space questions  (Read 4336 times)
Hening Bettermann
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« Reply #20 on: January 26, 2013, 06:15:48 PM »
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please what is "PRMG"?
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digitaldog
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« Reply #21 on: January 26, 2013, 06:42:34 PM »
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please what is "PRMG"?

PRMG is Perceptual Reference Medium Gamut. Since in the past, conversions using a perceptual intent were not well defined with respect to the source gamut prior to making its way into the PCS, this is supposed to be a less ambiguous color space (is that the correct term?, I would think it is) rather than some vendor specific gamut assumption and one that is unknown or defined as far as the user is concerned.

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Andrew Rodney
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MarkH2
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« Reply #22 on: January 26, 2013, 06:45:10 PM »
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please what is "PRMG"?

Probably the Perceptual Reference Medium gamut.  Info from the International Color Consortium here http://www.color.org/v4_prmg.xalter

Edit: oops, typing while you replied, Andrew.  BTW, great video, thanks.  The Colorthink plots of images vs color spaces are very instructive.
« Last Edit: January 26, 2013, 06:48:21 PM by MarkH2 » Logged
Hening Bettermann
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« Reply #23 on: January 27, 2013, 05:34:59 AM »
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Thanks to the both of you! - Hening.
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l_d_allan
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« Reply #24 on: February 26, 2013, 06:15:45 AM »
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A pretty exhaustive 37 minute video examining the color gamut of RGB working spaces, images and output color spaces. All plotted in 2D and 3D to illustrate color gamut.

Very interesting. Some was "over my head", but it did clear up some questions. Thanks.

I found myself wondering whether your ColorThink 3d images could show how Rendering-Intents like Perceptual and Relative-Colorimetric would adjust colors to fit within gamut. I'm fuzzy on how they work, and speculate that my understanding may very well be flawed. Do you have a video (or videos) related to Rendering-Intent? Black-Point-Compensation? Or video(s) on some other web-site you could recommend?

I did wonder about the down-sampling to get the original images to 300 pixels for ColorThink. It seems like there would be a LOT of averaging, and extreme values would get averaged and lost. I understand that ColorThink would really slow down with less (or no) down-sampling, but perhaps it could run overnight and then your video would just show the results. Or does the 3d spinning on axis slow way down?

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High resolution:http: //digitaldog.net/files/ColorGamut.mov
Low Res (YouTube): http://www.youtube.com/watch?v=n0bxSD-Xx-Q

Had trouble viewing the first ... even after removing the space between the colon and slash. YouTube worked ok.

« Last Edit: February 26, 2013, 06:30:24 AM by l_d_allan » Logged

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digitaldog
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« Reply #25 on: February 26, 2013, 09:30:28 AM »
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I found myself wondering whether your ColorThink 3d images could show how Rendering-Intents like Perceptual and Relative-Colorimetric would adjust colors to fit within gamut.

ColorThink plots gamut using Absolute Colorimetric intent which is what you want for viewing 3D gamuts (not necessarily for conversion of data to make a print, you then toggle between RelCol or Perceptual and pick the one that looks best).

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I did wonder about the down-sampling to get the original images to 300 pixels for ColorThink. It seems like there would be a LOT of averaging, and extreme values would get averaged and lost.


Shouldn't be a factor in terms of seeing the gamut. And there's no way you're feeding one let along multiple 5DMII rendered images at full rez in CTP!
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
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