VISA is primarily used to communicate with instruments via GPIB/TCP-IP/Serial/USB. In order to use easily VISA with an instrument over USB the instrument must adhere to the USBTMC spec. A camera is not likely to have this. Otherwise you have to use USB RAW, and that requires detailed knowledge of the data that is transmitted by the instrument. Manufacturers rarely give this information out. Normally they will provide a DLL to communicate with the instrument.
Thus, in your case, VISA is not going to be an appropriate API to use for a USB camera.
Out of curiosity, what prompted this question?
