Getting 600EX-RT slave to fire only via Pop-up Flash

[Ed_60D]

I have a 600EX-RT set up as slave and contolled by 60D using pop-up flash.  I have the 60D settings set for the slave to fire only as per pages 140-141 of the 60D manual.  However, in this setting the pop-up flash will still fire.  At the end of page 141, it says "Even if you disable the built-in flash from firing, it will still fire to control the slave unit".  Is there no way to disable the pop-up from flashing?  Otherwise you never really get single off camera flash.  Thanks.

[7D5D · Accepted solution]

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Is there no way to disable the pop-up from flashing?  Otherwise you never really get single off camera flash.  Thanks.

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Not if you want to trigger an off camera slave because it uses the pop-up flash as the means of triggering the slave. 

Yes you do get single off camera flash because even though the pop-up flashes, it is only a pre-flash to trigger the slave.  In this configuration the pop-up does not contribute to the actual exposure, this all happens before the shutter opens.

[Ed_60D]

7D5D

Thanks for pointing that the pop-up flash acts as trigger before the shutter opens.  I did a little test and sure enough, the flash from the popup does not affect exposure in the slave only mode.  

Cheers,

Ed_60D