Depends on the camera I would think... I'm not a Canon shooter, but one of my favorite features of my Nikon D90 is the programmable button next to the lens (right under the tip of my middle finger) that I have programmed to disable the flash. It only works when it's held in as I press the shutter, but it allows me to keep the flash turned on, but only use it on the shots I want it for.
Comments
As usual, "it depends", on what camera body you have.
On a 5DMkII = Yes
Menu > External Speedlight Control > Flash function settings > Flash firing > Enable/Disable
Good to know it's there for the 5dII at least (even if it's not readily available)
Thanks for the quick reply guys!
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