[Matz Chase]

Does anybody know if there's an option for turning off the on camera flash when shooting with an external flash in wireless mode? The on camera flashes in either master or control.

[karpati]

The flash is required to communicate with the external flash in either mode. When in controller mode, the internal flash does not add to the exposure, equivalent to turning it off. Hope this helps.

[SOldBear]

When in controller mode, the internal flash does not add to the exposure, equivalent to turning it off.

"Does not add to the exposure" is relative. If the object is close to the camera, or if the object has a reflective surface, the effect of the built-in flash, even in controller mode, is noticeable.

A workaround is to use something like this.

Or use an RF remote flash trigger instead of using the built-in flash.

[PANGU_yien]

actually, I'm 99% certain it's not relative. I think in Master mode it does the P-ttl pre-flash and then adds to exposure. In Controller it will still pre-flash to calculate exposure but I'm pretty sure it doesn't flash the second time, therefore not contributing to the exposure.

[SOldBear]

actually, I'm 99% certain it's not relative. I think in Master mode it does the P-ttl pre-flash and then adds to exposure. In Controller it will still pre-flash to calculate exposure but I'm pretty sure it doesn't flash the second time, therefore not contributing to the exposure.

Don't "think" nor take my word for it. Take a photo in front of a mirror and see it for yourself.

This falls into the case of "the object has a reflective surface" mentioned in my post above.

[Tanzer]

The contribution of the flash even in "controller" mode has been hashed to death and it most certainly is there. Whether it contributes enough to cause a problem for you is another matter, dependent on the relative power/position of your slave flash, and other things. Since I don't regularly take pictures of mirrors , it doesn't bother me at all.

Perhaps the OP's question was more about eliminating any flash, including pre-flash, from the on-board flash. I can see this as being a more relevant issue, than arguing about how much contribution the controller makes, when taking pictures of people, who are sometimes bothered by the pre-flash and blink. Unfortunately, that is not possible, except by using an RF trigger. For all intents and purposes, this implies running the slave in full manual mode.

The new Cactus V6 RF trigger will allow some remote flashes to be remotely controlled with respect to power level, although strictly speaking, they are still running in a full manual mode, with no automation whatsoever. Some photographers prefer to shoot in full manual, but given the nature of the question, I am guessing this is not the solution the OP is looking for.

[SOldBear]

I normally don't take photos in front of a mirror either, but I used to take photos of fish in aquarium tanks. The pre-flash strobe didn't bother me (it might the fish, however ), but the triggering strobe during exposure was the killer.

Of course I changed to using RF remote flash triggering device.

[AquaDome]

In this case, "wireless" doesn't mean radio-waves. It means pulses of light from the camera flash to control and trigger the slave flash. Yes, the camera flash may be visible. No, you can't turn it off.
I use Pocket Wizards or a hot-shoe adapter and a sync-cable when the pop-up flash on the camera needs to stay out of the picture. Sometimes its because I'm doing a macro for a product. Sometimes its because I'm using a long lens or a fish-eye and the lens casts a shadow in the scene.

That Nikon thingy probably isn't the solution you are looking for.

[Tanzer]

Oooh, I can definitely see how the optical triggering would be a big problem in an aquarium environment!