580 EX AF beam not working with 20D

The AF assist beam does not work on my 580EX when used with my 20D but it is fine with my 300D.

CF12 on the flash is set to "0", meaning AF assist beam is enabled and CF 05 on my camera (20D) is set to "2" meaning "Only ext. flash emits", (although I've tried 0 and 1 as well with no results). I've also tried all the camera bodys CF 04 functions thinking that the shutter button / AF controls may have something to do with it.

So unless I'm missing something that should get the beam to fire .. I've tried in all kinds of darkness, with lenses long & short, and with fresh batteries .. still no AF assist beam

Since it works with my 300D I can only think that the fault is with the 20D but maybe I'm missing something with the settings? Any suggestions?
Thanks,
Mike

Try switching your AF mode out of AI Servo.

Curtis N wrote in post #2981488
Try switching your AF mode out of AI Servo.

Curtis .. you've come to the rescue again, thanks.
Mike

mmahoney wrote in post #2981043
The AF assist beam does not work on my 580EX when used with my 20D but it is fine with my 300D.

CF12 on the flash is set to "0", meaning AF assist beam is enabled and CF 05 on my camera (20D) is set to "2" meaning "Only ext. flash emits", (although I've tried 0 and 1 as well with no results). I've also tried all the camera bodys CF 04 functions thinking that the shutter button / AF controls may have something to do with it.

So unless I'm missing something that should get the beam to fire .. I've tried in all kinds of darkness, with lenses long & short, and with fresh batteries .. still no AF assist beam

Since it works with my 300D I can only think that the fault is with the 20D but maybe I'm missing something with the settings? Any suggestions?
Thanks,
Mike

Besides having it on AF-One Shot you need to have either the centre or ALL of the focusing rectagles enabled. If you just select one of the outside rectagles the flash assisted AF won't work. If you do have One Shot and the centre/all rectagles selected then the camera will focus in total darkness. For this I prefer just the centre rectagle as I think that it's more precise.

DaveG wrote in post #2983848
Besides having it on AF-One Shot you need to have either the centre or ALL of the focusing rectagles enabled. If you just select one of the outside rectagles the flash assisted AF won't work. If you do have One Shot and the centre/all rectagles selected then the camera will focus in total darkness. For this I prefer just the centre rectagle as I think that it's more precise.

Should work with any focus point, it does with mine.

DaveG wrote in post #2983848
Besides having it on AF-One Shot you need to have either the centre or ALL of the focusing rectagles enabled. If you just select one of the outside rectagles the flash assisted AF won't work. If you do have One Shot and the centre/all rectagles selected then the camera will focus in total darkness. For this I prefer just the centre rectagle as I think that it's more precise.

You're probably thinking about the Sigma flash, Dave. I think that's how the Sigma 500 Super works with the more recent (versus older like 10D) EOS DSLR camera from what I recall reading here.

Dellboy wrote in post #2983863
Should work with any focus point, it does with mine.

I got this from Flash Photography with Canon EOS Cameras by NK Guy, http://photonotes.org …lash/index3.htm​l#afassist who is my reference source for all things Canon flash related.

He writes,"Also, if you have a camera body with multiple focusing points and your flash unit’s AF assist light isn’t lighting up in low light it’s probably because the AF light on the flash you happen to be using cannot cover your currently selected (ie: non-centre) focusing point. Many flash units have AF assist lights which can only illuminate the area around the central point."

I tested that with my 10D and it failed as predicted and I assumed that it was no different with my 20D or 5D.

Dave, which flash unit are you using?

One of the selling points of the 580EX is that it covers all the focus points on a 1D Mk II. I believe the aforementioned article was originally written before the 580EX was introduced.

I use a 550

Well that explains why your experience differs.

The Sigma Super is even worse. Center point only.

I had thatt same problem and it was in AI SERVO. Switched it and it was fine.

DaveG wrote in post #2984754
I use a 550

If it's the 550ex that you have the auto focus assist should work on all focus points except the top and bottom one ( in landscape ). Try it for youself it should give you a few more options when out flashing.