Showing results for 
Show  only  | Search instead for 
Did you mean: 

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.

03/14/2023: New firmware version 1.8.1 is available for EOS R6

03/02/2023: New Firmware Updates Are Available:

EOS R7 - Version 1.3.0EOS R10 - Version 1.3.0
02/24/2023: We've updated Share Your Photos

2/07/2023: New product announcements!

EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM
01/18/2023: New firmware version 1.1.1 is available for EOS R6 Mark II
01/09/2023: Help ensure your autofocus is properly aligned with a Canon Precision Alignment
01/03/2023: Welcome to CES 2023!
12/08/2022: New firmware version is available for EOS C70
12/07/2022: New firmware version 1.7.0 is available for EOS R5
11/22/2022: New firmware available for EOS R3, EOS R7 and EOS R10
11/16/2022: We're thrilled to be ranked among the Best Employers for Veterans in 2022 by Forbes.
08/31/2022: New firmware version 1.1.1 is available for RF 70-200mm L IS USM
08/09/2022: New firmware version 1.2.0 is available for CR-N 300
08/09/2022: New firmware version 1.2.0 is available for CR-N 500
07/14/2022: New firmware version 1.0.1 is available for CR-X300
06/10/2022: Service Notice:UPDATE: Canon Inkjet Printer continuous reboot loop or powering down
06/07/2022: New firmware version 1.3.2 is available for PowerShot G7 X Mark III
05/31/2022: Did someone SAY Badges?
05/26/2022: New firmware version is available for EOS-C500 Mark II
05/26/2022: New firmware version is available for EOS-C300 Mark III
05/10/2022: Keep your Canon gear in optimal condition with a Canon Maintenance Service
05/05/2022: We are excited to announce that we have refreshed the ranking scale within the community!
04/26/2022: New firmware version is available for EOS R5 C
03/23/2022: New firmware version is available for EOS-C70
02/09/2022: Share Your Photos is back!
02/07/2022: New firmware version 1.6.1 is available for EOS-1DX Mark III
01/13/2022: Community Update. We will be retiring the legacy profile avatars on 01/20/2022. Click this link to read more.