Quasimodo said:
I have a 580 EX II and a 430 EX II. I reason I got the ST-E2 was for its ability to master the other two flashes, and that it would give me the possibility to set the white balance correctly when shooting portraits. The way (at least in my head) that I would get the best white balance was to set up the flashes first, then to use an expodisc or if I had forgotten to bring it, a white/grey paper next to the subjects face, and use the ST-E2 to fire it off, while I have the camera and lens next to them to get the most correct reading. Is this a good way to go?
Seems reasonable to me. Personally, I just include a ColorChecker or SpyderCube in one shot of a series, shoot RAW, and set the WB in post.
Quasimodo said:
I keep reading here about using the ST-E2 without firing off the flashes.... What some of the postings here say is that it helps with focus assist.. Does it do anything that the AF does not do from the camera at its vantage point? I am a bit confused here. Ar you saying that the ST-E2 and the 580 EX II can help with additional focus readings. Or is this all wrong on my part, and that the focus you are talking about is: reading (focus) to get the right amount of light strenght?
The ST-E2, 600EX-RT, 580, and 430 flashes have a focus assist lamp - they project a deep red grid pattern of light that gives the AF system something to lock onto in dim light. Other flashes (320EX, 270EX, popup flashes) provide the assist by flashing the main strobe light, which many (including me) find distracting and annoying. FWIW, the new ST-E3 doesn't provide any focus assist.