When we acquiring the image from webcam whithin Matlab result depends
from Exposition Time, Contrast, Gain etc, many aquisition parameters
that control image properties. Webcams that I have tried (Logitech
Webcam HD C310 and Philips SPC 900NC) have automatic mode for set of
these parameters.  It is good for common purposes, but it is not
convenient if you like to compare different images.

I have try to control these parameters, but did not found how to
communicate between Matlab and camera driver. Correspondence with
webcam producer to obtain interface to camera driver (I have asked about corresponding DLL) gives no result as well.

If somebody knows the webcam models that allow such a control, please, give information about your positive experience.

Thanks for any information

I have found partial solution of above problem. At least, you can fix
webcam parameters till next program run if you will set
FramesPerTrigger parameter during initialization in following way:

vid.FramesPerTrigger = inf;

Good luck