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About the color value in color picker

Forum|Forum|7 years ago
November 26, 2018
6 replies
1885 views

Hello, I have a question about the color picker. When I draw a rectangle and double click the color picker which in tool bar and used HSB mode to choose a color. The color value will change when I close the color picker and open it again. My document is used RGB.

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T

Test Screen Name

Legend

You're right, HSL not HSB. But I believe it is going to suffer from the same quantitization effects.

T

Test Screen Name

Legend

A discussion of this from people who know more about this than me (and were trying to fix some software before concluding the problem was unfixable) possible rounding error when converting hsl to hex · Issue #1909 · sass/sass · GitHub " at extreme light/dark values, the color-space is very small - those are the corners of the RGB cube, so not much left to discriminate. There's a lot of quantization going on there, so in general values won't round-trip exactly."

Ton Frederiks

Community Expert

https://forums.adobe.com/people/Test+Screen+Name wrote
A discussion of this from people who know more about this than me (and were trying to fix some software before concluding the problem was unfixable) possible rounding error when converting hsl to hex · Issue #1909 · sass/sass · GitHub "

This is not the problem we are talking about. This is about HSL and the question is about HSB in the Illustrator color Picker.

T

Test Screen Name

Legend

Let's do an experiment with an online conversion tool. I don't trust most of these, but there is no colour management involved in HSB <-> RGB so let's run with RGB to HSV conversion | color conversion and HSV to RGB conversion | color conversion . Note: HSB is the same as HSV.

Let's feed it RGB 33E2FF (51,226,255). It converts to 189, 80.0, 100.0.

So let's feed it 189, 80.0, 100.0 to convert the other way. We get RGB 33E0FF which is (51,224,255)

Let's take that back to HSB again. Sure enough, we still get 189, 80.0, 100.0.

So you can see that the conversion is not simply 1 to 1. Not the same as Illustrator either!

Maybe it's using integer arithmetic, maybe there's an inherent quantitization, maybe it's a boundary condition at the edge of the HSB cylinder; I can't find a discussion of this and the formulae are a bit too complicated for me to guess. But anyway, it doesn't simply seem to be an Adobe bug.

Ton Frederiks

Community Expert

https://forums.adobe.com/people/Test+Screen+Name wrote
Let's do an experiment with an online conversion tool. I don't trust most of these, but there is no colour management involved in HSB <-> RGB so let's run with RGB to HSV conversion | color conversion and HSV to RGB conversion | color conversion . Note: HSB is the same as HSV.
Let's feed it RGB 33E2FF (51,226,255). It converts to 189, 80.0, 100.0.

That only shows that Illustrator does a better job

Converting RGB 33E2FF (51,226,255) it converts to 188,53 / 80 / 100

When you round this and feed it back you get an other value.

Illustrators Color Panel gives the most accurate values, the Color Picker is only accurate when RGB values are specified in an RGB document and CMYK values in a CMYK document.

Ton Frederiks

Community Expert

It has been like that for many versions.

The only reliable way to specify color is using RGB (or HEX) values in an RGB document and CMYK values in a CMYK document.

T

Test Screen Name

Legend

I don't think anything is wrong, it's all correct. Photoshop does not work in HSB, so when you choose an HSB value it is immediately converted to RGB. Then, if you look in the colour picker, the RGB is converted back to HSB. There are multiple HSB values for a single RGB value, because that's how it was invented. So, all normal, it converts the RGB (which you can see is the same) back to a different but equally valid HSB.

Both the HSB value you see translate to the same RGB value so they look the same in all situations.

Ton Frederiks

Community Expert

https://forums.adobe.com/people/Test+Screen+Name wrote
I don't think anything is wrong, it's all correct. Photoshop does not work in HSB, so when you choose an HSB value it is immediately converted to RGB. Then, if you look in the colour picker, the RGB is converted back to HSB. There are multiple HSB values for a single RGB value, because that's how it was invented. So, all normal, it converts the RGB (which you can see is the same) back to a different but equally valid HSB.
Both the HSB value you see translate to the same RGB value so they look the same in all situations.

I think there is something wrong.

Photoshop lets you specify any Hue angle when working in an RGB document, without changing it like Illustrators Color Picker does.

There is no reason why a single RGB value will be translated to multiple HSB values. Why would that be as invented? It is not like CMYK where black generation can give multiple combinations of CMYK translate to the same RGB color.

Illusrtrators Color picker is the problem, the Color panel does a much better job altough it will give you fractional values that when rounded are the same as Photoshop. Entering H: 189 in the Color Panel will give you 188,99

cinziamarotta

Participating Frequently

Hi,

The Color Picker can cause confusion because you can use different color model to edit a color but it'll change according to your document color profile.

HSB numbers only apply in the specific Color Space being used. If you change the color space, the same numbers will produce a different color. Those values change according to the document color space.

You can see that the hexadecimal value doesn’t change. It means it’s the same color.

c.pfaffenbichler

Community Expert

Sounds like the file might actually be CMYK (File > Document Color Mode > …).

Could you please post a screenshot showing the Status Bar set to »Document Color Profile«?

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