The command determines the shutter error distribution. The error
distribution is computed as follows. If 
has a total
reported exposure time of t1 seconds, and the shutter is
opened and closed 
times (including the beginning and
end of the exposure) and img2 has a total exposure time of
t2 seconds, and the shutter is only opened and closed once,
then the final shutter error frame 
is determined by:
An image and a contour plot of the error frame are produces.