Using Sigma super dg 500 wireless

[Henry Low]

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

[lostdoggy]

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)

[DavidEB]

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,