Short answer; NO.
Originally Posted by fehn
Long answer; the first is a "pre-flash" for the E-TTL (Evaluative Thru-The-Lens) metering system needed to calculate the required flash output to appropriately expose the subject. The second is the "real" flash that actually exposes the scene and is fired just before the shutter curtain closes.
You also have the same two flashes when you use 1st curtain or 2nd curtain with a fast shutter speed (i.e., 1/250), however they fire so close together that you see them as a single flash.
~ Newt ~
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