This article explains the settings and values for the Corona Tonemap Control shader.
The Corona Tonemap Control shader transforms the texture using the inverse of the current color mapping, effectively removing any postprocessing color mapping from it. This can be useful for displaying an emission / self-illumination texture that exactly matches the input bitmap in the resulting render under any color mapping. For this feature to work correctly, the color mapping cannot be changed after the render is started.
While the Corona Tonemap Control shader will work fine in most cases, there are some special cases where it may fail, for example, when using some LUTs, when using extreme Filmic Highlights or Shadows values, setting the Contrast value to zero, etc.
This is stated in the shader's UI.
Shader – This slot defines the texture map or shader that will be used for this shader.
Affect the shader by Corona VFB
Exposure – When enabled, only Exposure affects the shader.
LUT – When enabled, only LUTs affect the shader.
Tone mapping – When enabled, only the Tonemapping options affects the shader.
When no checkbox is enabled at all, the texture map or shader won't be affected at all by VFB Exposure, LUT, or Tonemapping.
Using the Corona Tonemap Control Shader.