Color inconsistency

jpmb76 · 2020-05-17 16:56

Can someone smarter explain to me why do I get such a inconsistent results across different programs?
After all they supposed to show same results.
Color in question is the one from Wikipedia page.
screenshot

Last edited by jpmb76 (2020-05-18 09:00)

den4b · 2020-05-18 08:55

Can you please elaborate what you are talking about?

Which colors, which programs, provide some examples...

jpmb76 · 2020-05-18 09:01

Yes, sure. Looks like I didn't attach a screenshot to my post. Edited now.

den4b · 2020-05-18 10:22

jpmb76 wrote:

Looks like I didn't attach a screenshot to my post. Edited now.

It is starting to make more sense now with the screenshot, but the details in the screenshot appear quite faint. Can you upload a higher resolution/quality screenshot, if you still have the original?

Can you explain what you did, which applications are involved, maybe focusing on the most apparent discrepancy?

jpmb76 · 2020-05-18 11:06

Ok, new screenshot below
screen4K

I was working on a logo for local bushcraft group and wanted to pick a color for a background from the website. Then I noticed that HEX and HTML values are swapped, (topic for another conversation).
At the time I was working on Affinity Designer but since all Affinity programs are using same engine, Affinity Photo is used in my screenshot.
Anyway. Copied CMYK values from color picker to Affinity and noticed that color is off even though value entered matched the one from color picker, in this case it's (17,0,11,64).
Measured the new color using color picker and noticed that CMYK value is different.
So what I did, I opened Affinity Photo (top, left), Photoshop (top, right) and GIMP (bottom, right), created rectangles filled with hex color (4D5D53), that's the one on the left. Then I created another rectangle, the one on the right, and filled it with CMYK color value from website (17,0,11,64), which supposed to represent same color.
Measured all of them.
Only GIMP showed same values as color picker, hence just one rectangle.
All three programs were running same color profile.

Hope all this makes sense.
Affinity Designer

den4b · 2020-05-21 22:01

Thank you for a detailed description.

I started doing some tests and was able to confirm your findings for a subset of mentioned applications, i.e. Colors, GIMP, Photoshop.

Default installations of GIMP 2.10.12 and Photoshop 2020 were used, with #4D5D53 html color code. RGB and HSV values agree in all 3 applications. Colors and GIMP agree on CMYK values (17,0,11,64), but Photoshop disagrees (68,48,62,30).

My hypothesis is that Photoshop is applying some kind of color management feature to the CMYK values. I will investigate further, but I am not an expert in Photoshop. In the meantime, you could ask on Photoshop and GIMP forums for an explanation of a discrepancy between these two applications.

jpmb76 · 2020-05-22 09:31

Since I don't work in Photoshop (I like to own my software), my primary editor is Affinity, but even Affinity is showing different results for RGB and CMYK.
I wrote an email to Serif (Affinity publishers) describing the problem and my guess is folks at Serif are scratching their heads right now as I still wait for reply.
One more thing. Colour entered as RGB or HEX values represent different colours than colours entered as CMYK, at least in Photoshop. Gimp somehow understands this and shows same colour in both cases.
In Photoshop and Affinity when colour is entered as CMYK value, when checked with Colors (colour picker) shows yet another colour.

jpmb76 · 2020-06-04 09:28

RGB document:

CMYK document:

These are taken from Photoshop. I get similar results in Affinity:
RGB document: yellow (RGB 255,255,0)(CMYK 6,0,96,0)
CMYK document: Yellow (RGB 255,242,0)(CMYK 0,0,100,0)
Colors Lite results:
RGB document: (RGB 255,255,0)(CMYK 0,0,100,0)
CMYK document: (RGB 255,242,0)(CMYK 0,5,100,0)

den4b · 2020-06-06 09:43

Welcome to the Color Management space.

Photoshop and other professional graphics editing software offer a wide range of features to deal with color management, which include assigning a color profile to an image, interpreting embedded color profile within an image, and converting between different color profiles and color modes.

Photoshop uses predetermined default color profiles for different color modes, which can also be adjusted in the Color Settings, where you can select a color profile and other attributes for different color modes (or color models), e.g. RGB, CMYK, Gray.

Color profiles (or ICC profiles) describe the characteristics of color input and output devices by means of well defined conversions to/from a profile connection space (PCS), either CIELAB or CIEXYZ, which is then used as a common intermediate space for converting between two different color profiles.

The (den4b) Colors tool does not currently deal with color profiles. Conversions between different color spaces are performed using common linear remapping algorithms, i.e. simple maths. In contrast, conversions performed in Photoshop would use color space remapping according to the selected color profiles.

A conversion sequence using linear remapping algorithms:

RGB -> [linear remapping algorithm] -> CMYK

A conversion sequence using color profiles:

RGB -> [sRGB / IEC 61966-2-1:1999] -> LAB -> [Coated FOGRA39 / ISO 12647-2:2004] -> CMYK

Some worthy references:

P.S. The content in this post and additional information can be found on the wiki → Colors: Color management.

Last edited by den4b (2020-06-06 11:06)

den4b Forum

#1 2020-05-17 16:56

Color inconsistency

#2 2020-05-18 08:55

Re: Color inconsistency

#3 2020-05-18 09:01

Re: Color inconsistency

#4 2020-05-18 10:22

Re: Color inconsistency

#5 2020-05-18 11:06

Re: Color inconsistency

#6 2020-05-21 22:01

Re: Color inconsistency

#7 2020-05-22 09:31

Re: Color inconsistency

#8 2020-06-04 09:28

Re: Color inconsistency

#9 2020-06-06 09:43

Re: Color inconsistency

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