Caught between gamma and brightness
You want to adjust a mix of gamma, brightness and contrast, or if available, simply use curves.  Gamma impacts the way in which the output intensity corresponds to input intensity, but if you don't also adjust other settings, you will still end up clipping key details outside of either the signal range of your signal or the display range of your display.

Using curves gives the most flexibility to adjust the amount of contrast in each portion of the range of signal intensity so that you can see everything clearly, however it is also possible you are simply near the effective limit of the range your display can produce depending on where the information you need contrast for is.

I suggest starting by trying to make sure your contrast or black point (on curves), is set such that you can tell the difference in shadow detail and then trying to adjust the brightness or white point (in curves) to get it so you can just tell difference in light detail and then try adjusting gamma to give you the needed spread.