Diff between on-Flash compensation and cam compensation

[Steveo31]

I don't shoot digital, but most EOS (D)SLR bodies are the same in terms of the buttons and features...

On my EOS-3, there is a flash +/- button (same as meter mode). On the flash (550EX), there is the +/- setting. When the one on the camera is set to -1, the graph in the viewfinder shows the flash at being -1. When the flash is set to -1 and the camera to 0, same graph. I'm wondering if one is different than the other?

[scottbergerphoto]

They both function the same. Some camera bodies do not support FEC on the body, and you have no choice but to set it on the flash. They are additive. If you set +1 FEC on the camera and +1FEC on the flash you will get +2FEC. That's why if you set it on the flash you don't see it on the body.
Regards,
Scott

[PacAce]

They both function the same. Some camera bodies do not support FEC on the body, and you have no choice but to set it on the flash. They are additive. If you set +1 FEC on the camera and +1FEC on the flash you will get +2FEC. That's why if you set it on the flash you don't see it on the body.
Regards,
Scott

I'm not sure how it is with the 1DmkII but on the 10D, if FEC can be set on the flash, then it overrides the FEC that's set on the camera. It's either the FEC of the flash (550EX) or the FEC on the camera (420EX) that's used. So, for what it's worth, on the 10D at least, FEC is not additive.

[Steveo31]

Ah cool. Cause in a pinch I don't think I would have the time to look up... hit the right combo of buttons... blah blah. On camera compensation is much faster.

Thanks for the replies! :D