Image Acquisition Overview
When a trigger occurs, the toolbox acquires frames from the video stream and logs the
      frames to a buffer in memory, a disk file, or both, depending on the value of the
        LoggingMode property. To work with this logged image data, you must bring
      it into the MATLAB® workspace. 
The following figure illustrates a group of frames being acquired from the video stream, logged to memory and disk, and brought into the MATLAB workspace as a multidimensional numeric array. Note that when frames are brought into the MATLAB workspace, they are removed from the memory buffer.
Overview of Image Acquisition
