Do you mean in GeForce Experience? If so, some are not using it all all because they have either no use or this is taking taking unnecessary resources.
But more importantly, adjusting brightness and/or colors via a post-processing Shader is not solving the problems I’m highlighting in this post and this has nothing to do with the subject. Please let me try explaining what is happening, I’ll let you search online the technical terms.
Just looking at the output (to keep it simple I’ll use only 1 gray value from 0 to 1): the simulator is rendering a white square spanning 5 pixels which are displaying as a gradient of grays from 0.8 to 1.2, but it is clipped to the [0,1] range for display obviously and as expected:
Source: 0.8 | 0.9 | 1.0 | 1.1 | 1.2
Output: 0.8 | 0.9 | 1.0 | 1.0 | 1.0 (clipped)
a) Applying a Shader to lower the luminosity by 0.2 from the source (in FS2020):
Source: 0.8 | 0.9 | 1.0 | 1.1 | 1.2
Output: 0.6 | 0.7 | 0.8 | 0.9 | 1.0 (pre process -0.2)
Display: 0.6 | 0.7 | 0.8 | 0.9 | 1.0 (clipped) <— no loss of signal between output and display
b) Applying a Shader to lower the luminosity by 0.2 at the output (after FS2020):
Source: 0.8 | 0.9 | 1.0 | 1.1 | 1.2
Output: 0.8 | 0.9 | 1.0 | 1.0 | 1.0 (clipped)
Display: 0.6 | 0.7 | 0.8 | 0.8 | 0.8 (post process -0.2) <— loss of signal, it is just dimming the clipped white
NB: this is a simple illustration of 1, and only 1 of the problems with post-processing this (there is more like quantization errors, color shift, etc…)
In other words:
The rendering is done in an unclipped linear space, then it is tone mapped, and then converted to a non linear sRGB color space which is clipped for display, and this is why you can’t post-process what I’ve written above otherwise I wouldn’t have requested it.