Upload & Sell: On
I have a set of 285's in the mailk right now and I was wondering If i need to buy anything extra to trigger these flashes off camera with a 7d or if the 7d pop up flash can do that?
The pop-up flash always emits preflash pulses, even in manual mode, so it won't work with non-Canon flashes.
You could use a sync cord to trip one of the 285s, and fire the other one with an optical sensor like this one that has a Vivitar-style connector:
A more flexible and reliable method, but at higher cost, would be to use radio slaves: one transmitter for the camera, and a receiver for each flash.
Pocket Wizard, Paul C. Buff, Elinchrom, and Phottix are good brands, but if you're just starting out the Cactus v5 is a bargain: