Is it possible to shut the flash off and still use the 580 for autofocus
I believe you need the flash on to allow the flash to coordinate the autofocus assist light with the camera.
You can set the flash to manual, power it down to 1/128th, and point the head up or even backwards so that the flash doesn't contribute to the exposure. The assist light will work as you wish. (You could even fire the flash into a blackened hood at 1/128th power without too many problems methinks.)
I am curious why you would want the autofocus assist light with no flash at all?
What kind of distances are your 580exs from your shooting position?
It is interesting that basketball is one of the activities that folks complain about the ST-E2 being not very effective.
Many shooters use PWs when shooting in arenas. I know the local college hoops arena is set up to trigger with PWs or a similar device.
I do a lot of work in abandoned buildings with very low light but its really hard to manually focus the camera and with the 580 I can focus in on a subject in a complete darkness.Has anyone actually done this before because I followed the directions in the manually but it still fires.Thanks Owen
Program Mode in the EOS cameras, with flash, is designed to permit handholding so the shutter speed will not go below 1/60th I believe.
EOS flashes work much better in Av, Tv or Manual mode for most purposes.
1 Series cameras do not have the little mountain, little head, little flower choices, of course.......
I'm using a Canon 20d and I just want to use the 580 kind of like a ST-E2 just to help me focus in very low light I followed the instructions in the manual but the flash still fires
Just a quick question, do the other Canon flahses (ie, the cheaper ones) allow you to do this as well, use the flash as AF Assist? I'm trying to figure out which flash I'll be getting to go with my XTi.
I too would like to know. I have a 430ex. Also - can the on-board flash be used to focus (but not fire)?
The ability to use the flash for autofocus, but not to fire for the shot, is set by custom functions and is not a limitation of the flash unit itself. The 20D/30D line on up have the custom function needed to disable the flash, but use the infrared focus assist lamp. The Rebels (XT/XTi) do not.
P.S. This limitation caused me to buy the ST-E2 for natural (low) light focus-assist. Ironically, what really happened is I went back to using flash, because I could use it off-camera, producing much better results.