20D, 70-200 sigma, f2.8

shooting from 7:30-10:45 p.m. it's about as dark as it is going to get
by 8:30.

granted this was a small High School field from sidelines, with really
crummy lights. The fields I usually shoot at have more light, and some
have enough light for Television cameras, not this one.

I used a coupld of flash cards a SanDisc 1gig and Lexar Plat II 2gig

No Flash used, generally 800 f 2.8-3, 125-200. in the End ZOnes it was
unbelievably dark and I had to go to 1600.  I am pretty close to
everything, and don't want a flash going off and affecting the players.

anyway on a burst of about 3-7 images the luminosity, brightness/hue
seem to drop ocassionally.  really noticable with the grass.

in a sequences of 7 shots, one towards the middle maybe 3 or 4, the
grass will almost be a shade of brown instead of green.

any enlightenment?

mikel