Most lights pulse at twice the frequency of the AC power supply. If you take a picture during the dark part of the cycle, it will be a bit darker than the bright part of the cycle.
One fix for this is to use an acquisition rate that is a fraction of your light pulse frequency. For example, if your AC power is 60 Hz, you could use 120 fps, 60 fps, 40 fps, 30 fps, etc. since they all divide into 120 evenly. This will only prevent brightness fluctuations during continuous acquisition.
If you are starting and stopping your acquisition, you would want to make sure the exposure time (or shutter speed) is a multiple of a full cycle of the AC power frequency. For example, with 60 Hz power you could use an exposure of 1/120 second, 1/60 second, 1/40 second, 1/30 second, etc. This will guarantee consistant exposure every time.
Bruce
Bruce Ammons
Ammons Engineering
