Flash exposure - an easier way?

I have started shooting weddings with my 20D, 580EX, and two 550Es's. i still find that in order to get decent pictures of non metered shots i have to set the flash exposure (in ETTL Mode) on the persons face, or other object in order to get a great shot. the overal metering just doesnt work with point and shoot. the problem with this is when a subject is moving its hard to target their face and even when you do, they have already moved past that metered point. am i doing something wrong?

Anyone? does my post make sense..?

What do you mean "non-metered shots"? Remember that your camera's always going to give you a meter reading based on available light, not on the flash. It'll only feed in flash based on the feedback to E-TTL II from the pre-flash. If you've got the bride in there, all that white's going to make a big difference. Similarly, but oppositely, if the groom's there in his tux, the black will influence the readings.

Best you read the EOS Bible, linked from the eos flash faq in this forum. That will answer most of your questions.

Jon,

i understand that all shots are metered, what i meant by that was posed, metered shots.

anyway, if a bride and groom are walking toward you, and you just point and shoot without first taking a flash exposure reading, the picture with either come out over exposed or under exposed depending on what the camera sees, white or black. but if you preflash expose the face, then recompose the shot, your exposre will be almost right on. does this make sense? my issue is, i have heard many say they just point and shoot at weddings with their 20d and 580ex and it works perfectly. i dont understand how taht can be.

I think I may know what's happening to you. When you press your shutter halfway to lock focus on the eyes or face, you probably recompose the shot so these features are no longer in the center circle and when you fully press the shutter, the ETTL pre-flash is taking it's meter reading from something else. I recommend setting your ETTL metering to average instead of evaluative. I find that works better.

a good assumption, but i actually press the flash exposure button. when i press the flash exposure button on the face, then recompose.. all is good.

i'm simply talking about compose and shoot, no flash exposure first. All E-TTL in both cases.

beaconlightboy, what settings are you using on the camera when you take these shots? (and what mode do you set your flash to?)

Flash set to E-TTL (and i set the flash mm to auto, hope thats right)
Camera on manual
could be any combination of Fstop/shutter speed, normally 5.6@60

Thats why they have the Manual mode. In a wedding, get an exposure for most of your shot and bracket, or open or close the Fstop according to distance. Play with it a few times, and it becomes 2nd nature.

so i should use manual flash, and just learn the distances / fstop combo's huh.

Worked for me for years. 10' iso 100,=f? based on your strobe. 15' will be a little lower and 20' might be 5.6. After you get use to it, not very hard to do.

i will give that a try. thanks for your input guys.