I modified the value of user_sat from -ve to +ve, however the effect is weird. -ve values do not cause any effect on the image while positive values do not cause obvious effect. The +ve values, for an extreme effect, say 9000, only make the image being darker and more red.

I am wondering the usage of user_sat here. Should modifying saturation can make the image change from a black and white image to a very deep colored image?? It's because I see other image processing software is working like this when adjusting the saturation.

I'm using LibRaw 0.15.0-Beta4.