Inspiring

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Confused With Info Panel

Forum|Forum|8 years ago
June 24, 2017
2 replies
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I created a new Document in Gray Gamma 2.2

I filled the layer with RGB 128,128,128

Placing a target point on the gray layer, the Info Panel Reports

RGB 128,128,128

K: 43%

HSB: 0,0,50%

Plotting the point with a Curve, the Input value reads 145

Can anyone explain why the K: value is not 50% and why the Curve Input in not 128

Ian

info

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Correct answer D Fosse

Numerical values across color modes relate to your working spaces.

If you use gray gamma 2.2, you also need to set RGB values in a color space that actually uses gamma 2.2 - the only one is Adobe RGB. ProPhoto corresponds to gamma 1.8, and sRGB to sGray.

The dot gain grays have no RGB equivalent. They're supposed to compensate for ink spreading when it hits paper.

There is in fact no particular reason these numbers should match. They're not supposed to. If they do, it's mostly by accident.

D Fosse

Correct answer

Community Expert

Numerical values across color modes relate to your working spaces.

If you use gray gamma 2.2, you also need to set RGB values in a color space that actually uses gamma 2.2 - the only one is Adobe RGB. ProPhoto corresponds to gamma 1.8, and sRGB to sGray.

The dot gain grays have no RGB equivalent. They're supposed to compensate for ink spreading when it hits paper.

There is in fact no particular reason these numbers should match. They're not supposed to. If they do, it's mostly by accident.

davescm

Community Expert

Hi Dag

You are absolutely right (as I would expect from you on a colour issue ). I've changed the correct answer to yours.

The fact that I was using Adobe RGB as my color working space - caused the values I looked at to match .

However, I wonder why it has been implemented this way. Whilst of course the K value at 50% brightness, or "RGB" number will change according to the particular gray profile, it makes no real sense to have different values for the same pixel reported in the info panel , the histogram , the color picker and the curves dialogue.

I would have thought that on switching to a grayscale document profile - all the panels should switch to that common reference, including the color picker which should really only allow picking from gray when in grayscale mode.

Dave

I

IanBarberAuthor

Inspiring

Right. I actually thought that was the way it did work - that any open document should override the working space for that color mode. But I haven't checked this, and if not I agree with you.

What I cannot understand is this...

I create a New document in grayscale using my Working Gray: Gray Gamma 2.2

I then fill that document with RGB 128,128,128 and this is the result

I do the same only this time, I select RGB and Use Adobe RGB 1998

I then fill that document with RGB 128,128,128 and this is the result

Isn't Adobe RGB 1998 and Gray Gamma 2.2 supposed to have the same Gamma Value of 2.2 ?

Should they not display the same values ?

I appreciate that if I had chosen ProPhoto RGB instead of Adobe RGB the values should be different because ProPhoto has a Gamma value of 1.8

Workflow

When I am scanning black and white Negatives, I am outputting them from the scanner in a Gray Gamma 2.2 profile and then bringing them into Photoshop which is set to Gray Gamma 2.2 in the Color Settings.

What worrying me is that, what I thought should be 50% gray is actually been reported by Photoshop at 43%