Count that flash.
 

Having made a flash count gizmo I proceeded to check all my cameras. Canon cameras fire 2 flashes no matter what mode. But Nikon D90 and 3100 has got me stumped. From a normal distance (12 feet} they fire 2 flashes, but close shots, they fire 3 flashes. I have an expensive book on D90, but no mention of this. Not that it matters for normal use. :confused:

They are probably pre-flashes for ttl metering and red-eye reduction.

Certainly not red-eye reduction, Steve, the focus-assist light is used there.

Wait until you get into off-camera flash. I've seen a plot that shows no fewer than 14 pulses from an on-camera SB-800, and 3 from each off-camera unit. It's at [URL="http://www.nikonians.org/forums/dcboard.php?az=show_topic&forum=154&topic_id=38452&mesg_id=38452&page="]Nikonians[/URL], if you're interested. You'll probably have to register to see it.

As you say, it's best not to worry about these things.

Chris