Here's what I use for my outdoor wedding work.
If I'm using the camera's own internal meter, I'll point it at a gray card or some sort of "middle tone" value of illumination that is in the scene. This should get me an average meter reading that is in the ballpark. Let's say this is your f/4 at 1/200 using ISO 400. I'd put the camera in MANUAL mode, and dial in these settings (which will be locked since it's in manual).
I would then turn my 580 on in AUTO-ETTL MODE, and dial in something like FEC 1- stop, or 1/3-stop...... something less than " 0 ".
Why? Once I get my correct ambient meter reading, I like to just throw out a splash of light that is sufficient to open up shadows in the eye sockets and elsewhere. I don't want a NUKE in the face white blast. It is not flattering.
But - if you have a hand held meter, that is even better yet IMO.
At the position of the subject, I take an INCIDENT meter reading. With the dome covering the hand held meter's sensor, I point it back at the camera. This gives an extremely accurate reading since it is measuring the light FALLING on the subject, not being reflected off a white shirt, black pair of pants, plaid blouse.... you get the idea; all of those reflected readings will give you different readings which can give you very inconsistent readings.
Once I get my hand-held meter reading, I use the flash in the same manner as described above. I dial in "FEC - " to taste, which will give me a pleasant amount of modelling. Hope this helps. - Stu
sdipirro wrote in post #8953915
OK, I've always been mixed ambient-flash challenged. Some sort of mental block in understanding this. Let's say we're doing this manually (no ETTL). Using the camera to meter the background, let's say you get camera settings of f4, 1/200, and ISO 400 for the background to be exposed the way you like. Now you're going to introduce the flash off-camera to illuminate the subjects "the way you want." Supposed I wanted to meter the subjects and trigger the flash to take the guesswork out of it. What am I looking for in terms of meter readings to properly expose the subjects in front of this background? Thanks.