On board flash - How to disable when going wireless! (7D)

[MOmilkman]

For some reason my on board flash started going off when it is popped up when using my 580EXII flash wireless with the built in wireless feature on the 7D.

I have not had previous problems with this but now for the life of me I can not figure out why it has suddenly started going off at the same time as the off camera flash.
I'm sure it has to be something simple that I will slap myself for when someone tells me.

Obviously, I have to have the flash popped up for the wireless flash to work and under the flash settings I have it enabled and just the one wireless flash selected and not the on-board and wireless flash icons. (which would obviously be my problem if I had selected that)

Any ideas? I've browsed the manual 3 or 4 times and I've come up empty so far.

[OsmosisStudios]

The flash has to fire to trigger the off-camera flash, but you should be able to set it to not contribute to the exposure. The flash will still fire, but not during exposure.

[MOmilkman]

Ok, thanks for the response. I must be going crazy. Seems like when I first started using the flash wirelessley, the on board flash didnt go off, just the speedlight. Maybe it did and I never saw it... hmmm...

So your saying in order for the speedlight to work wirelessley it has to see that flash of light from the camera? I always assumed there was some type of frequency that was transmitted for communication purposes.

[OsmosisStudios]

The information is transmitted through IR, like a TV remote. The flash simply acts as a trigger. It's necessary. It's the same on the Nikon system.

[MOmilkman]

Ok great thanks. I can't believe I never noticed it before.

The first time I noticed it was a couple weeks ago when I decided to family photos of myself, my wife and daughter, and was staring into my camera, which I rarely do.

[Merlyn]

Now you folks have me stumped. Just today, I am using my 7D with my 580 and I know the camera flash prefires to communicate with the 580. OK, I am taking a pic of a motorcycle speedo and the glass on the speedo reflected the built in flash from the camera.Caught me off guard. The 580 was mounted on a light stand. Camera was about 3 feet from the glass of the speedo. I did check to see if the camera flash was not set to fire for exposure and it was not. I am going to try and recreate the situation again tomorrow.

[OsmosisStudios]

Make sure you set the flash on the 7D to simply act as a commander and not contribute to the exposure. Failing that, for critical things like this, I carry Nikon's SG3-IR flash blocker: it fits into the hotshoe and blocks the light from the flash but still allows it to trigger the external remotes (albeit sometimes affecting the triggering). I don't know if it'll fit properly on a 7D, but I dont see why not.