Black point, white point, brightness, contrast : which formula between them ? -- RAW, Post Processing & Printing in photography-on-the.net forums

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Oct 19, 2010 14:55 | #1

I'm looking for the formula that can give me the brightness and contrast values from the values of the white and black points.

I have noticed in DPP, when you change the white point or the black point in the RGB histogram, the values of RGB brightness and contrast are adjusted automatically. So I'm looking for the formula that is used there. I' have tried to search for a linear relation but it is not a linear relation...

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chauncey

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Oct 20, 2010 06:19 | #2

Your question is not very clear, what are you trying to achieve?

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René Damkot

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Oct 20, 2010 07:26 | #3

Looks like "brightness" moves the curve straight up and down without affecting the angle, and "contrast" changes the steepness "rotating about" the center point (what's originally 128,128).

Looks pretty linear to me...

Brightness - 100: Blacks at 0;127, whites at 255;128
Brightness + 100: Blacks at 128;0, whites at 127;255

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chauncey

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Oct 20, 2010 08:02 as a reply to @ René Damkot's post | #4

I knew that...yeah right I did. :lol:

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