At each q, we decide the number of filters that is required and the
image acquisition time, and acquire 4 images. Immediately after
tuning of the instrument, we acquire
USAXS image (sample in the beam, with filter, beam on).
Optics (sample not in the beam, with filter, beam on).
Dark field (beam off).
Flat field image (sample not in the beam, q = 0, with filter,
beam on, image acquisition time may need to be shortened to
prevent saturation).
Step 3 of #26 (USAXS Imaging Operations)