Examples: Ambient, iTTL-BL, and iTTL
Prepared 2006-01-11 by Bill Claff

Not the best subject but a good example I think of how flash can affect a shot.

Nikon D70 100-300mm w/1.4xTC @140mm
Top: f/11 1/50s ISO 1600 no flash
Middle: f/11 1/60s ISO 1400 Built-in iTTL
Bottom: f/11 1/500s ISO 1600 Built-in iTTL
Post processed for white balance, exposure, contrast, and very slight sharpening.

I like each one in it's own way.