580 Flash ...what is the mm setting?

[Matt30D]

On the 580 Flash there is a setting where you can change the mm? What is that? I am shooting a 17-85...is it the distance from the camera to the subject or the area the flash will cover?

[cdifoto]

It's the focal length of the lens. On Auto it'll change as you zoom so that the beam is widened or narrowed as needed for maximum efficiency. It only works when shooting direct flash though. Bouncing disables it and fixes it at 50mm (I believe) while showing -- on the LCD.

[Matt30D]

So If I am shooting direct flash and the group is 80-100 ft n front of me..do I just let the flash do the work?

[cdifoto]

That's kind of a loaded question. Assuming you're only referring to the zoom setting and not the complexities of E-TTL metering, subject distance doesn't have much to do with the zoom setting. The zoom setting on the flash determines the angle of coverage of light, and ambient conditions determine what you can get away with doing. In daylight, you can project a narrow beam (105mm is the smallest on the 580EX) even with a wide angle lens because it's not the primary light source. Do the same at night and it'll look like a car's headlight.

[Matt30D]

I understand..so if I am taking a picture of a big shot of a high school instrumental group on stage with adquete lighting (400 ISO)- F11-SP-1/30,,,would I need a flash?

[jrsforums]

I understand..so if I am taking a picture of a big shot of a high school instrumental group on stage with adquete lighting (400 ISO)- F11-SP-1/30,,,would I need a flash?


That is also a loaded question.....i.e. the answer is "it depends"

Nothing will replace learning the capabilities of your equipment. Try it out, with different variations and tunings or parameters until you understand what it does and what you can "tweek" to adjust for different conditions.

Practice, practice, practice.....