Consecutive photos show variation in exposure and white balance. A series of 6 may cycle three times. They all have the same exposure, Fstop, shutter speed
Looking at the histogram shows a moderate shift between images.

Shooting HS football on dimly lit fields. D300, either 300mm or 70-200, F2.8, Manual settings, 2.8 and between 1/250 and 1/500, ISO 3200+ either Auto WB or Pre-set. Do not believe I have bracketing set.

Someone has suggested that the 60 cycle of the lights changes exposure but I don't this. Camera store and Nikon rep can see the problem, but have no explanation.

Any idea?

charles