Participant

Question

Photoshop problems with displaying color properly/ brush blending mode problems

Forum|Forum|1 year ago
May 31, 2024
6 replies
602 views

Greetings,

All of a sudden I am having issues using colors (for digital painting) in photoshop:

Problem 1 - the color blend mode for the brush has stopped working properly; instead of just changing the hue/saturation of the base color, it is also changing the brightness or value of the base color; example of the problem attached

Problem 2 - color picking stopped working properly; i tried to avoid the color blend mode problem by manually picking another hue with same luminosity value in the color picker (with normal brush blend mode); but when I apply the new hue with same luminosity it shows as either darker or lighter than the base color; then when i color sample that new hue from the spot where I added it on the canvas it shows a different luminosity value than the one when I first found that color in the color picker ; example of the problem attached

I tried restoring default Photoshop settings, reinstaling the same version of Photoshop, reinstalling another version of Photoshop, turning off and on the use of GPU in preferences. I also tried deactivating native canvas in preferences. Nothing worked.

I am using RBG color mode.

color profile I am using

Windows

This topic has been closed for replies.

D Fosse

Community Expert

According to the litterature, ProPhoto covers about 90% of Lab. So this is apparently in the 10%.

It might also complicate things here that Lab is known to not be perceptually uniform, especially in the blue region. This is responsible for the blue > purple shift one can sometimes observe when remapping intense blues to lesser saturation.

In short - try again with numbers that are within gamut of whatever color space you're in. I wasn't able to see any shifts when I did.

O

Orgrin37757918dwtcAuthor

Participant

Hey thank you for your reply. You will find a screenshot of my default color settings at the bottom of my reply. The problem with the brush color mode still changing the luminosity or brightness of the base color is still there even when I use colors which are within the gamut of my color profile. My understanding of the color blend mode for the brushes is that it applies new hue and saturation values but keeps the exact same luminosity value of the base color. However this is not happening on my screen. Here is an example in the attached image below.

It might be that this is something that is normal and that I didnt notice it before but as a digital illustrator I switch between RGB and Dot Gain (black and white) mode pretty often to check values in my painting and I never noticed this problem until recently .

D Fosse

Community Expert

If you're working in sRGB, I can give you some numbers to try for that purple.

The original Lab purple (51 57 -101) is way out of gamut in any RGB color space. It's unreproducible.

If you want to stay inside sRGB gamut, you can try Lab 51 42 -76. This is one number short of the sRGB gamut boundary (blue 254 instead of 255), so it won't change.

Now, you may still see a small discrepancy because of the difference between Lab L and RGB Luminosity. Don't know, haven't tested it, but it's not unlikely.

D Fosse

Community Expert

OK, it's actually out of gamut in ProPhoto as well. ProPhoto clips to 255 in the blue channel at these Lab numbers. And so the numbers change when you revisit.

I tried with more realistic numbers, and those numbers don't change.

(what I wrote in the first post is correct, but doesn't apply here. This is simply out of gamut).

D Fosse

Community Expert

Edit - hang on. Got to my machine to look at these colors. That purple in your second example, defined as Lab numbers, is out of gamut in sRGB and Adobe RGB. I need to take a closer look in ProPhoto. Note how the marker (the small circle) is right at the edge of the sampling field? That means it's out of gamut, and will be clipped to the nearest reproducible color.

What RGB color space are you working in?

O

Orgrin37757918dwtcAuthor

Participant

You will also find attached images which will help explain things further.

O

Orgrin37757918dwtcAuthor

Participant

Hey Fosse,

Thank you for your reply but you didnt understand the problem correctly. I was not talking about the luminosity blend mode. I was talking about luminosity as a property of color in the color picker. Color is the name of the blend mode that is not working properly for me. If you have some free time please read the text once again with more focus.

Thank you in advance,
Aleks P.

D Fosse

Community Expert

I'm not at my machine right now to test, but I believe this is expected and correct behavior.

Luminosity blend mode is a custom formula that weighs the green channel about 60%, the red channel about 25%, and the blue channel about 15% (not actual numbers, but ballpark).

This gives a result that is similar to the L channel in Lab, but isn't identical. One could ask why they don't simply use L, but that's the way it is.

So with Color being the "inverse" of Luminosity, this is what I'd expect to see.

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