Using Sigma super dg 500 wireless

Ok i am trying to sue my Sigma super DG 500 on my 20D wirelessly.

I am trying to trigger it using my oncamera flash.

It works flawlessly. But one problem. Because I want to use my oncamera flash to trigger the sigma slave flash, i dont want the oncamera flash to have any affect on the picture. meaning, is there a way ot make the oncamera flash not appear in the picture while still wanting to trigger the slave?

Thanks,
Henry

Actually the on camera flash will preflash to trigger the dg 500. The on camera is not capable of being a master it will not transmitt a wireless signal. I think the only ones that can is the 550 and the 580. You can use the 500 to be a master and trigger another 500 or 420/550/580 (inconsistently). To do what you want you need a Canon ST-E2 to trigger any 420/550/580 (consistently)

you can ALMOST do it. very, very close.

set the sigma 500 super to manual slave, figure out the requisite flash output using f-stop = distance/GN (GN = guide number) at ISO100 and dial in the desired flash output.

at the camera, dial in Flash Exposure Compensation = -1 or -2 stops. press "flash exposure lock" (* button if not using custom function 4.1 or 4.3) -- this will discharge the modeling flash and the sigma will also fire. Wait a few seconds for sigma to recharge, then shoot the picture.

The camera will think it sees a lot of flash output from the modeling flash (it will in fact see the on-camera flash + the sigma) so it will put out a weak flash for the main exposure. That coupled with -2 stops of FEC will produce a barely noticeable flash from the camera. Effectively all your light will come from the sigma.

Usually I go the other way around, and dial in +2 FEC just to get the on-camera flash to be noticeable.

the canon 550/580 etc EX flashes can't be used as manual slaves as far as I know. a minor advantage to the sigma.

if you're using a rebel, you'll need the hack firmware. If you're using custom functions to reconfigure the * button you'll need to turn those off.


enjoy,