Problem with new D5100 found..

Stacey, just something you might want to check. It is possible to accidentally set the camera to bracket the exposure automatically. That is, depending on your bracket compensation, you could take six shots and have one under by .5, one on, one over by .5 . . . and then one under by .5, one on, and on over by .5 . . . forever - and frustrating the hell out of anyone experiencing it! The camera, depending on setting, could tweak the shutter speed, f stop, or both. Turn the camera off and then on again and this "problem" repeats. Now go to your manual and change this. Of course, I am just guessing (based on a ton of experience).

Most clerks at most ANY camera shop are ill prepared to offer sage advice. Sad, but VERY true.
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Steve Bingham
www.dustylens.com
www.ghost-town-photography.com