Sounds like CanonsÂ’ T3's Flash Exposure Lock function, which fires the flash under manual control before the actual exposure, to determine the proper exposure setting.
Brooklyn-Camera wrote:
First time using the pop up flash and a slave. The camera is the Canon T3 1100D and the slave flash is a TT560 THINKLITE speedlite, off band I believe. When I try to take a photo with the slave and pop up the pop up flashes as you focus. This causes the slave to fire, is there anything I can do to stop this. The slave has settings M, S1 ans S2. Any and all help will be appreciated.