4. I mins and I maxes

A frame can be used to generate an I max and/or I min location which is
available for subsequent exposures. If these are not set, the positions
are not updated and previously set locations are still valid. Note that
specifying a previously determined I min or max as a pointing reference is
another parameter (see subareas and CCD image references). It is also not
possible for a frame to use its own I max or I min for a pointing reference.

Note that the coordinates and values of the I max and min are available
in the sequence language if you want to do anything clever with them
after an exposure.