Hello,
I did some testing on Gamma correction and on tone mapping with Poser.

My test scene was a unit square with a pattern of RGB colors (full and half intensity), plus some greyscale squares. The only light in the scene one sun, shining vertically onto the square. 
I did renders with 50% light intensity, 75% and 100%.

The camera pointed directly to the square.

This is what I got:

Poser 7 or Poser Pro without gamma correction.
 No surprise: The resulting image at 100% light intensity was almost identical to the texture (exactly concerning the color values, differences only due to unprecise camera positioning).

With 50% light or 75% light, the RGB values were just multiplied by this.

Poser Pro with gamma correction (using 2.0 as gamma for simplicity): As expected, the color values were exactly what you would expect when squaring them. Also every color channel treated separately / independently.