Episode 195: Whose RGB?

rgb
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Colo(u)r ist the topic this time. You are in for a ride from the electromagnetic spectrum to the biology of color vision and the infamous Mantis Shrimp. (Link to the fabulous Oatmeal!)

Grassmann’s Law gives a clue how to create a color sensation in the brain by mixing up some wavelengths out of the spectrum. The CIE finally defines what is visible for a “Standard Observer” and Microsoft & HP (sRGB) and Adobe (Adobe RGB) build their color spaces on that foundation.

Elle Stone, Bruce Lindbloom and Cambridge in Colour help along the way, passing a Black Body emitting radiation according to Planck’s Law at 6500K just to give us a White Point.

Then I organize a shootout between sRGB and Adobe RGB – and I’ll stick to sRGB for the forseeable future.

Finally I cover the question of Intent while converting between different color spaces – Perceptual or Relative Colorimetric?

Links

Elle’s fine writeup about All the Colors.

The Color Space Viewer (at the bottom of the page)

Pascal’s tutorials about color management on Linux – really hands on:

https://encrypted.pcode.nl/blog/2012/01/29/color-management-on-linux/
https://encrypted.pcode.nl/blog/2013/11/24/display-color-profiling-on-linux/
https://encrypted.pcode.nl/blog/2013/04/14/display-profiles-generated-from-edid/

The TOC

00:00:00 Intro
00:00:15 Submit to GIMP Magazine
00:00:50 Light as part of the electromagnetic spectrum
00:01:43 Biology of color vision
00:06:14 World Champion of Color Vision: The Mantis Shrimp!
00:06:40 Grassmann’s Law – mixing colors from spectral primes
00:07:22 CIE 1931 Color Space – the standard observer
00:09:00 Elle Stone’s blog – a lot about color!
00:09:50 sRGB
00:11:40 D65 – the White Point for sRGB
00:11:56 Black Body Radiation and White Points
00:13:44 Bruce Lindbloom has a Color Space viewer
00:14:30 Adobe RGB (1998)
00:15:50 Why not ProPhoto RGB?
00:16:20 Preparing some test shots in the lab
00:16:59 Comparing sRGB and Adobe RGB camera setting
00:18:42 Conclusion – stick to sRGB
00:19:34 Converting between color spaces
00:20:06 Intent: relative colorimetric or perceptual?
00:21:14 Consequences
00:23:10 Winding down
00:24:09 EOF

Meet the GIMP Video Podcast by Rolf Steinort is licensed under a Creative Commons Attribution 3.0 Unported License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

13 thoughts on “Episode 195: Whose RGB?

  1. Hi Rolf

    I guess the Adobe RGB images look dull on your screen because color management has not been turned on on your operating system (though I thought Linux would handle that even better than windows). With color management turned on, you should (almost) not be able to see a difference between the images.
    All the same, your message to use sRGB as a rule of thumb is the best way to go for most people, because, as you already mentioned, most people don’t have the hardware and the knowledge to use other color spaces. Me included, although I do have a Adobe RGB capable screen at home :).

    • Color management is switched on – a lot of programs display the images properly. For example the Gnome Image Viewer – visible in the video. But a lot of browsers don’t care and don’t talk with the color management. So there is a big chance that an image published on the Web in Adobe RGB will look dull on the screen of the viewer.

      I assume this will change with time.

  2. Great introduction and elaboration!
    Thank you!

    I think the Color space variance – different coordinate systems to show them – was a bit too much unnecessary information though. It will probably confuse people who are completely new to this stuff, and won’t help get the point across (which was already made before that).

    What I was missing in the color space definitions was the actually human-visible space. We saw sRGB and adobe RGB compared to each other, but not to the actual human visible space.

    In the conclusion you point out that sRGB is the only choice for editors as they publish as digital content.
    Obviously, there is also print. And as far as I know, and the sRGB article on wikipedia supports me here, in professional printing Adobe RGB is used in that world as well.
    Obviously, for most people sRGB is the sane way to go. But I felt like you missed naming a valid product target there (e.g. you create/publish images for printing).

    • I found no 3D-model of the visible color space to compare to the others – but I assume it will be at least as depressing as the little triangle in the horseshoe…..

      Going into (professional) printing and working from RAW files is a higher level than I wanted to cover here. I’ll do that in a later video.

      sRGB is IMHO the way to go if you are not really know what you are doing. Of course one can improve from that.

      • Given that sRGB is the industry standard colour model for monitors & the Web, it makes sense to work within it, & even if you prefer a workflow based on another model (Adobe being the common example), you’d still need to convert to sRGB for use in those environments anyway.

        • It can be quite an advantage to work in a larger color space to avoid clipping. But of course you need then a higher bit depth than 8 bit to avoid banding and you have to convert finally again to sRGB.
          This all has to be reconcidered when GIMP 2.10 is available.

  3. Absolutely excellent show once again 🙂

    With regard to the sRGB vs AdobeRGB topic, you’re totally right sRGB is the only fully compatible and safe choice. While AdobeRGB does have advantages, it’s best avoided unless one has a thorough understanding of color management concepts.

    That said, banding typically isn’t too much of an issue for AdobeRGB just yet. On the flipside, Pro Photo RGB is typically used with 16bit to avoid banding though.

    Here are some general notes on color management particularly on Linux:

    https://encrypted.pcode.nl/blog/2012/01/29/color-management-on-linux/
    https://encrypted.pcode.nl/blog/2013/11/24/display-color-profiling-on-linux/
    https://encrypted.pcode.nl/blog/2013/04/14/display-profiles-generated-from-edid/

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