What is unity_ColorSpaceDouble used for?

Graphics Shaders & Materials
1

In UnityCG.cginc I found some defination:

uniform fixed4 unity_ColorSpaceGrey;
uniform fixed4 unity_ColorSpaceDouble;
uniform half4 unity_ColorSpaceDielectricSpec;
uniform half4 unity_ColorSpaceLuminance;

I guess they were some variables for color space conversion, but how to use them, any sample? what does each vector component stands for?

2

No body use them before?

3

It is used for gamma

4

I used unity_ColorSpaceDouble when I convert my colour space from the Gamma Space to the Linear Space. You can search how to make Gamma Correction in a shader.