40D built in flash question

Hi guys. Okay, this may be a noob question (this is first dslr). I just got to fully test the new 40D today and didn't pay attention to the builtin flash. After taking some outdoor shots and moved into indoor shooting, I started to notice the flash's behavior when activated (i didn't notice/wasn't paying attention with my first few low light shots with flash). I'm wondering if this is normal. When I half push the shutter, it autofocuses the lens and the flash will "prime?" itself by flashing like 5 consecutive times (real fast and sounds like your shuffling cards) then it stops. It does it about the same time the camera autofocuses. Then i fully engaged the shutter to take the picture and it flashes normally. I checked the manual for a setting but couldn't find anything related to my experience. does this happen to your 40D?

doh never mind..i just found the answer. its the af-assist beam feature. i just turned it off.

That is the Autofocus-assist function (AF Assist). In order to focus in low light, it pulses the flash to light up the scene while it tried to get the focus correct. You can disable it in the custom-functions (the 'AF Emmits' option)

By adding an external flash, like the 580 EX II, you get a better version of autofocus assist from that unit.
If you turn the built-in assist off, most likely you'll end up unable to focus in dim scenes indoors.

You can also use AF Servo to turn it off.