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How can I stop the pre-exposure flash on a 4Ti


I was given a 3rd party flash that has a slave mode. When I use the built in flash to fire the slave, the slave fires in response to the pre-exposure flash (I can see it through the view finder) and the resulting picture is obviously really dark. If I lock the exposure using the * button on the back of the camera, I can wait a few seconds and let the slave recharge and then take the picture and the slave fires during the actual picture. I emailed this question to Canon support and they responded with directions on how to switch the exposure lock button to the "Set" button??? I then called Canon support and the gentleman said just set the built-in flash to "Manual" mode but when I tried that, the pre exosure flash still fired...


Does anyone know how to get the built-in flash to fire without the pre-exposure flash firing first?





The first thing to check is that you have the C Fn for AF assist beam turneed OFF. If that's not it check that it isn't related to Red Eye Reduction being turned on.


"A skill is developed through constant practice with a passion to improve, not bought."

@cicopo wrote:

C Fn for AF assist beam turneed OFF. 

This is it. I think it was C.Fn 7-1. But you'll find it in the C.Fn.

Nope, its not the AF assist beem. It has something to do with exposure. When using the built in flash in low light it sends out a very brief flash and the camera uses this pre flash to set the strenght of the real flash for a proper exposure. I know this because if you push the exposure lock button (*) it fires the pre flash (and the slave) but then locks the exposue so when you push the shutter button you get just the correct flash and the slave fires too and you can see the slave flash in the resulting picture.


Thanks for your reply!

Thanks for the reply but niether the AF assist Beam nor the red-eye beam affect it. It may be that this camera has a mind of its own and has decided to drive me nuts...


I don't have a 4Ti, but it looks like it should function as a master.  Are you sure you have it set up properly?


Not to push more purchases on you, but the old Yongnuo RF-602s are great wireless triggers and cost next to nothing.  Looks like they're going for about $25 for a transmitter/receiver set.  Then you can just pick up more receivers if you get more flashes.  It won't do eTTL (but the new 622s will), but I doubt your third party flash will either.  Radio triggers are a ton of fun, it'll totally change your photography.  I hold no responsibility for the money you'll end up spending on multiple flashes and triggers.  I'm up to 5.  Heh.

I think you may be on to something. Thanks for the suggestion.