My guess: the camera turns on, dumps a lot of current on Q1, voltage across Q1 rises, voltage across the camera drops, the camera turns off and tries again.
You need a bigger Q1, something like BD433 at least, or more base current, or both.
It's not unusual for compact digicams to take up to 1A peak.
Even better solution is to use a MOSFET. The ubiquitous IRFZ44N might do if its "typical" performance curves are anything to go by, if not, I'm not sure what popular equivalent "logic level" switching MOSFET might be, maybe somebody else will know.
MOSFET has the advantage of much lower voltage drop and no base drive, so higher overall efficiency. You may care about such things if it's battery powered.