Light absorption test - Is it possible using Gimp?

[Ofnuts]

When you use halogen, the color temperature changes with output so the spectrum changes, and the camera isn't built to be uniformly sensitive, it favors the greens.You get a better light source by switching on and off multiple tiny sources such as LED, or by feeding LEDs with a square wave (frequency high enough so that a cycle is negligible compared to exposure duration) in which you change the duty factor.

Gamma is explained here: https://en.wikipedia.org/wiki/Gamma_correction