On Wed, Feb 7, 2018 at 6:15 AM, Máirín Duffy <duffy@fedoraproject.org> wrote:
Hi Chris,

On 02/06/2018 06:09 PM, Chris Murphy wrote:
On Tue, Feb 6, 2018 at 9:17 AM, Máirín Duffy <duffy@fedoraproject.org> wrote:

3) Green as a color for digital display is somewhat problematic as it is the
color with the poorest coverage in the sRGB color gamut, meaning across
various displays it can appear very different, making it an inconsistent
color for branding. (see [7], figure 4 for a diagram of the gamut)

And more sensitive to hue error in achromatic color than chromatic
color. So there's really all kinds of ways for color matching to fail
and just avoiding greens isn't going to improve the chance of a color
match.
LOL I was actually hoping you might jump in with a more informed background on the issue :)

I'm not saying green should be avoided entirely, but if it was the main color of a background.... I'm just not sure it works out the best. One of the Fedora "Four Fs" is a bright green and we've had some issues with it. (Maybe more with printing than display tho)

It depends on the scene, there is such a thing as memory colors, like green grass. So even if we're nut fussy about accurate rendering of green in general, we can become fussy via object recognition, and finding green grass being a bit too blue or too yellow and finding that objectionable. The same problem happens with skin tones.

 
Maybe incorporating the "four f's" colors into one of the backgrounds could help make the background more colorful though. We've tried to stay pretty blue because the few times we tried to veer off we got a lot of negative feedback, although the latest background (jellyfish) has a blue-purple gradient and I've honestly not seen a bad thing written about it.

The biggest problem we're likely to face are images with smooth gradients. Laptop panels are shit, and you'll see more complaints about banding/posterization due to images that expose defects resulting from the low bitdepth of most laptop panels. This is easy to deal with, just add noise. If the scene is blue sky, pick the image with even a few wispy clouds to break up the gradient. Or even in this case maybe avoid blue sky images because the sky isn't really blue, it's more cyan and displays don't do a great job of reproducing that color, and it's also a memory color. If it tracks a bit blue or a bit yellow on some displays, people will abruptly become aware of it.

Likewise, neutral images will be a bugaboo because the gray balance of most consumer displays meanders throughout the tone curve. A neutral image will just expose panel deficiency, unless the image can depend on being duo or tri toned, which actually might be kind fun to play around with... or totally insane.

There's a whole area of psychophysics research on what constitutes emotionally neutral imagery. It's important to have various test images that don't evoke an emotional response when doing human testing in image quality evaluations because you don't want the person injecting unrelated bias into the results.

I suspect what's going on with the latest background is two fold: it's such an artificial blue-purple color that it in no way makes people try to compare it to a memory color, it's so chromatic it's already divorced from reality. This is actually a rendering sought after by Fuji Velvia film affectionados. It would render forest, garden, and underwater scenes in totally unnatural fairy tale chromatic color. There was not even the pretense about accurately reproducing the actual scene. The other reason is the jellyfish image probably is succeeding at being emotionally neutral. And it has some low frequency noise throughout that breaks up the gradient so any panel deficiency isn't noticeable.

Anyway I would think less about specific hues involved, and more about whether the objects in the scene have certain specific hue expectations in rendering. Making the rendering more dreamy or ethereal, while also emotionally neutral, will help you get away with a lot of things you have no control over.



--
Chris Murphy