occasional overexposure with Speedlites

[arlin411]

I've seen several threads about exposure issues with speedlites but none that are quite what my issue is.

I have a 580EX and a 600EX-RT.  I use them on a 5D Mk II and a 70D.  Regardless which flash and which body, the same thing occurs.  I shoot in manual exposure with the flash on-camera on ETTL, no compensation. It'll be exposing fine then it will start to over-expose by a stop or two.  I've found that if I turn off both flash and camera then fire them up again the exposures will be correct.  

It doesn't do this often--maybe once in 100 shots, but if that shot was THE shot then it matters!

I'd appreciate any thoughts on this.

-Arlin

[diverhank]

If it happens only 1 out of 100 and doesn't get worse I wouldn't worry about it.

Apparently there was some problem with the ETTL function...that couldn't properly measure the correct light output required.  Maybe there is some miscommunication between the camera and flash...

or, if you've been using Pocket Wizards, I read that it can potentially causes damages to your flash IGBT circuit which regulates the light intensity of the flash.  Without IGBT, the flash will output at full power, therefore overexpose your images.  

[arlin411]

 If it were just the one shot in 100 it probably wouldn't be such a big deal, but once it starts over exposing it continues to until I do something about it, like turn off the flash and turn it back on again.  So if I don't check the LCD regularly I could  lose a whole sequence. 

 I don't use Pocket Wizards.  

[RobertTheFat]

If you have an E-TTL camera and your flash is set to TTL mode, you will get severe overexposure.

[Waddizzle]

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@arlin411 wrote:

 If it were just the one shot in 100 it probably wouldn't be such a big deal, but once it starts over exposing it continues to until I do something about it, like turn off the flash and turn it back on again.  So if I don't check the LCD regularly I could  lose a whole sequence. 

 I don't use Pocket Wizards.  

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If you recompose shots, then it could be your metering technique.  

Hopefully, you won’t get the chance, but the next time it happens, check that the camera is still communicating with the flash.  Make sure that there is no foreign debris on the flash shoe to cause a bad connection.

Finally, but I gotta ask.  Are you locking the flash onto the hot shoe?  I know a guy who wasn’t and had problems.  ME.

[Tim]

Hello arlin411, 

I understand that your Speedlite 580EX and 600EX RT overexpose images when used with your EOS 5D Mark II and EOS 70D.

You mentioned this occurs while shooting in Manual mode.  Are other modes susceptible to the same overexposure?  If possible, you might try shooting in Program mode to see if the same thing occurs with either camera.