Question: Blender Color Strangeness

[spikeyxxx]

@blanchsb that is probably what they use in Blender then, but it is just a formula; there is no such thing as an absolute Gamma correction formula; ‘Gamma’ is a bloated word, meaning something like ‘to the power of’… a ‘Gamma’ of 1 (default in Blender Gamma Node!) would mean: raise to the power of 1, also known as: do nothing.

Here’s an image squared twice and put through a Gamma Node, set to 2 another two times, can you tell which is which? (of course you can’t, because they are the same!):

[spikeyxxx]

@blanchsb when you also want to use negative integers, it is customary to use the so-called two’s complement (you can look that up) system, which, in a 8 bit system, would mean: 0000 0000 to 0111 1111 gives 0 to 127 and 1000 0000 to 1111 1111 gives -128 to -1.

[Shawn Blanch]

@spikeyxxx Gamma correction varies based user selection in the Render Color management tab (default is set to sRGB correction). But the value is also dependent on what the color value is. In most cases with blender the internal gamma correction is somewhere along the lines of 2.2. That node in your picture is in addition to that internal color correction value for most workspaces in blender.
From the older Blender 2.79 manual:

The latest manual just states it is being done but the value of internal correction should still be the same.

[Shawn Blanch]

yeah it consumes the last bit in the series for the negative sign. Two’s compliment is used in our IO modules and confused me for the longest time. You still are working with 8 bits but you lose half of the range in either positive or negative direction (no longer 0-256.)

[Shawn Blanch]

Where’s Jonathon to pitch in. I figured he’d be all up in the color space know-how lol.

Thanks for the comments all.
I will be able to confirm that formula does the proper conversion in the other color spaces this weekend when I make a proper
HEX to RGB to linear (gamma and un-gamma corrected) converter in blender to be used as a module.

Goal is to have something available in Python to go from one end to the other and get the same value  every time that matches for the color. Working in the color spaces is difficult without the proper conversion formulas in place.

[spikeyxxx]

@blanchsb you are riight, but I just wanted to say that Gamma is, in itself, a meaningless word:

[Shawn Blanch]

Too bad they still use it daily in my blender workspace lol

[spikeyxxx]

Indeed! Unfortunately Shawn! 

But the reality is, that when it comes to digital color, 97.7301% (this is just an estimate) of the people (including PS and so developers), do not know what they are talking about (and that includes me, of course!).

[Shawn Blanch]

You can add me to that group. I at least figured out the brush colors though. I can successfully convert HEX to brush RGB in Blender every time now using a random HEX genetator.

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