580exII - way to use its AF-assist without firing?

[aparis99]

I think sometimes for receptions and other dim environments i'd like to be able to AF and stay with the dark feel.

My Tamron 17-50 f2.8 cant always focus and using the popup flash just strobes and is annoying and i think it doesnt focus very well b/c my pics usually turn out a little soft and OOF maybe.

I'd like to be able to sometime use the 580ex for throwing an IR beam and hopefully getting perfect focus. Is there a way?

[canonphotog]

Look in your 40D menus. I'm pretty sure you can set it to emit, but not fire. That way you get your AF focus beam. Might have to put it in manual to keep it from emitting a ETTL burst.

[kay188]

Focus with flash on, keep holding button, turn off flash, shoot, turn on flash for next focus.

Ya that's inconvenient, but that's the only way I do it and can think of.

And it's not an IR beam. If it was IR, we wouldn't be able to see it.
It's just a red light.

[dpds68]

Yes in the Cam Menu you can turn it off from firing .

[kay188]

Yes in the Cam Menu you can turn it off from firing .

That's for turning off the the flash from strobing to AF.

I don't think OP is wanting to turn it off.
I'm assuming OP wants to be able to use the AF assist light from the 580EX flash unit to help focus, and have the 580EX NOT fire flash at all.

As if you have a flash unit on and connected to the camera, it tells the camera you want to flash.

[dpds68]

You can turn of the flash while still retaining the AF light Page 103 in the 40D Manual .

[Shamir]

go manual.. Then set your flash at its lowest power .. saay 1/64 and turn the head backwards.. it should cause no visible effect most of the time..

[kay188]

You can turn of the flash while still retaining the AF light Page 103 in the 40D Manual .

Well, problem solved!

[dpds68]

Here it is .

http://i44.tinypic.com/t8vngo.jpg

[aparis99]

thank you sir!

[bacchanal]

Keep in mind that the AF Assist beam only works in One Shot mode.

[dsldub]

Can it also be done on a 30D? I checked under custom functions #7, and there is something similar to that.

[k_strecker]

Can it also be done on a 30D? I checked under custom functions #7, and there is something similar to that.

yes it can be done on a 30D