How does the Metz auto mode work? Do I set an f stop on the flash - can I set it for f4 and get a constant f4 light off camera on a stand at wedding reception with ebay trigger? What about bounce on camera?
Metz auto mode works like any auto thyristor flash metering. A sensor on the flash reads light reflected back from the subject and quenches the flash when it 'thinks' there is enough light for proper exposure. With the dedicated Metz 58, there is communication between the camera and flash, so you don't have to set the f stop on the flash. You can set your f stop on the camera, which is communicated to the flash and you will theoretically get a constant f4 light. Theoretically, because even auto thyristor, which some claim is more consistent than ETTL (don't know what cmaera you are using), still needs flash compensation, mostly for subject lightness/darkness and backlighting (anything that would fool the sensor). You can use the flash in auto thyristor mode on a stand at a wedding with an ebay trigger as long as the trigger works well. Theoretically, auto thyristor isn't supposed to work well in multiple flash situations, but in practice it works--you just have to figure out how to compensate your flash(es) to preserve a ratio, if that is what you are after. However, for room lights at a reception, I've found manual flash is the best. Bounced flash is supposed to be automatically taken care of by the sensor, but again, some compensating fine turning can be necessary.
