Low Lighting shooting help

[neuroanatomist]

Oh so the flash lowers itself judging by how much light the shutter lets in? Wow, didn't know that but it makes sense now

Not exactly. FEC lets you adjust the flash exposure relative to what the E-TTL II flash metering decides is optimal. Nothing to do with the shutter, per se - aperture and shutter speed control the ambient contribution to the image. At 1/1000 s in a dark environment, ambient contribution will be close to nil.

If you're relying on automatic flash exposure, it will determine flash intensity for the foreground subject based on the preflash reflected back from the subject (assumed to be at the selected AF point, or in the center if no point is selected). That's what FEC changes.

Might want to read Syl Arena's excellent book, or NK Guy's, and/or spend some time over at:

http://strobist.blogspot.com/2006/03...g-101.html?m=1