On all National Instruments' analog frame grabbers, the ADC will apply a gain of either 1, 1.33, or 2 to incoming signals in an attempt to increase the image's resolution over a given pixel depth. For instance, if you have a linear LUT where a black pixel is 0 and a white pixel is 255, and the image you're acquiring is dark (close to zero), our ADC will probably apply a non-unity gain to the incoming signal so that the values will be distrubuted over more of the pixel values. Since this is built into hardware, the only way to really circumvent it is to make sure your LUT already takes your image environment into account. So, if you want to focus on darker shades, perhaps a Logrithmic LUT would be appropriate. This will designate most of the pixel values for describi
ng dark shades and leave fewer to describe the lighter ones.
