First photo's with flash for....

[arith]

The subjects are not good but I couldn't find anything else: The first off camera flash looks ok and was predictable with the flash about 2 metres to the left on 1/16 power and diffused; I can't seem to stop the body flash from firing and had to disable AF assist.

The second has me confused since it is on camera bounced 45 degrees forward with a reflector to direct a little light at the subject. I had to reduce my aperture and increase fev to +2. Is this to be expected?





cheers

[Colin Southern]

Hi Arith,

If the on-camera flash is acting as a master controller then it will fire a pre-flash even when it's set not to fire (this is how the master communicates with the slave; it's not via infra-red as a lot of people think).

Also (one of those little trivia things) - I've found that the preflash can also be part of the main exposure. (If you don't believe me, try this ... set your camera to 1/200th - wide open - MAX ISO. Take a shot in a dark room - preferable of something white (I used a white leather couch) without a flash. Attach a flash - set to master mode, but set not to fire. With no slaves present, take another shot. In theory there shouldn't be any difference, but in my tests there was).

With regards to your "FEC", dialing in some compensation is normal. Compared to Nikon, Canon tend to have a more subtle fill flash philosophy - so if you want more "pop" in your foreground subject then having the FEC +1 is pretty normal. Also though, the exposure of a scene with flash is no different to one without flash in that it tries to expose the scene as if it were a medium gray - so white objects tend to under-expose and black objects tend to over-expose.