Problem with 30D exposure--I need advice!

While shooting high school football Friday night, I noticed a problem with my exposures. I was shooting in high-speed continous, manual exposure (of the same play) and the exposures would be different--varying by almost a stop.

I was shooting with a 30D, 70-200 2.8 IS, ISO 1600, shutter speed 1/250 at 2.8, white balance at K. At first I thought it was the spotty lighting at the field. But when I noticed it more and more, I shot a burst of five frames of a close up of the track that circles the field, and the exposures and color seemed to shift a bit in each exposure.

Sounds like I ought to send it back to Canon for a check up. I bought it new in January and have about 6k actuations. As a semi pro, who has purchased about $5K worth of Canon gear in the last 5 months, what's the likelyhood Canon will send me a loaner?

Thanks in advance for your help! Hank

Hank, this sounds like a custom function thing...check out this thread (it turned out that he was having the same prob. with his 40D)

https://photography-on-the.net/forum/showthre​ad.php?t=371147

(he thought it was focus but if you read far enough into the thread everything resolves around the exposure not locking) It gets figured out too...

Is there any flourescent lighting at the field? Floros experience some color shifts as they 'cycle' through a spectrum of colors at 50/60Hz. It is not immediately obvious in one-shot mode as the camera does a great job of balancing for it (in AWB mode too, not K!) but if you lock your camera on K and shoot during different parts of the cycle, you will notice the shifts. Drive mode in particular would give you a very good sequence of back-to-back frames to compare. It happens when I'm shooting indoors under flouros and I bracket a sequence of shots.

Do not adjust your camera... well ok, shoot single frames and AWB, but that's probably not what you wanted!

As usual, you guys are awesome. I reshot under better, and more controlled, lighting conditions and I could not duplicate the problem. It must have been those funky lights at the stadium. THANKS for your help!