The camera parameters are directly set from Programs/SMDIMAP/SMDCAM accessible in the ``Start'' menu of ``Windows'' (also accessible in Civit). This is the frame period in s (close to the exposure time of an image), the offset and electronic gain (1 or 4).
Longer frame periods (exposure times) result in better image luminosity. The particle displacement during the exposure time leads to a wider correlation curve which may by itself improve the measurement. The exposure time must be however sufficiently short to avoid streak effects, which would lead to excessively flat correlation curves, whose maximum is not well defined. A good compromize would be to choose an exposure time for which the maximum displacement is about one pixel.
Then the luminosity and contrast (related to offset and gain) are to be chosen to avoid saturation for both minimum (no point with zero value) and maximum luminosity (no point with luminosity 256 for the Pulnix(2.3) or 4096 for the SMD(2.3). Check the image histogram (visible on the Civit screen). Do not use the option ``antibluming'' for the SMD at low luminosity: it produces spurious vertical lines.
Of course the background must be black, and no significant reflection from the free surface must be visible. Otherwise it will result in spurious correlation peaks in CIV algorithms, associated with the velociy of the background (generally zero). Adjustment of contrast and luminosity may help suppressing these effects. Note that there is a possibility of introducing a mask(3.2.4) in the processing, to remove edges in which the image would be polluted.
An example of excellent image is given in fig. 1. Note the grey scale ``texture'' of the image, in which individual particles cannot be really distinguished. Sharp contrasts (like black and white images) are not favourable, as well as images with rare isolated particles.