MATLAB: Image acqusition toolbox ; exposure time

Question

Im using a USB camera with winvideo driver. I want to change the exposure time via MATLAB image acquisition toolbox.Exposure is between -13 and 4. What are these numbers refer?For ex; i chose 4 and exposure time is 16 sec.

Answer 1

Those times are possibly log2 of the exposure time. 2^4 is 16