Curious to know something, I've been playing with both of these functions and they appear to be about the same. A friend who operates Xl1s for his business typically shoots in Auto Mode and sometimes in TV mode and compensates shots with the AE Shift on the Xl1s, appears that it's easy access similar to Exposure lock for the GL2.

With this in mind, techically is there anything really different between these two modes to brighten up or darken up scenes?

Thanks,

All roads lead to Rome. But, yes, exposure lock and AE serve very different functions.

Background: Unlike Sony and Panasonic, Canon had a long heritage in still photography before it ever produced a video camera. Expecting to attract many of their still camera customers to video they adopted the same program exposure modes for their video cameras that they had long used for their still cameras. That's where Tv, Av, Green Box and AE come from.

AE, "Auto Exposure", can be thought of as a way to tell the camera to automatically under- or over-expose the frame, with respect to the factory defaults. When coupled with one of the program modes (Time-Value "Tv", Aperture-Value "Av" or Green Box), AE modifies what the camera considers as correct. It has no impact when using Manual exposure.

Exposure lock enables you to use one of the program modes (except Green Box) to establish your desired exposure and then to lock-in the shutter speed and iris combination, preventing any the camera from making any further adjustments. So, to the extent that AE impacts the program modes, exposure lock is related to AE indirectly.