Since getting the T2i, I've strictly subscribed to the "orthodoxy" of this camera—set it to manual the day you get it and NEVER use AUTO.

I've done this for months and am comfortable with it...but I recently got into some more "run-and-gun" shooting situations (I was shooting a mountain bike ride)...and I really started getting irritated with how slow full manual shooting was—in conjunction with using Live Mode for focusing.

Another issue is trying to see the LCD in bright sunlight—without a viewfinder, it's incredibly hard to judge exposure.

So I started flipping through the manual (yes, something we should all do more often but rarely do!) and noticed that when shooting in AUTO, AE Lock is right there and incredibly easy to use. It's also easy to cancel and re-engage during a shot. And I thought, "What's wrong with this?"

So I ask the community—what's wrong with shooting in AUTO mode with the use of AE Lock?

Ditto for Quick Mode focusing—I understand it doesn't give you the control that Live Mode does (and the screen goes blank for a second)...but man, it's a LOT faster...and in random focusing tests around the studio, it appears to get focus pretty darn close every time (plenty good enough for run-and-gun shooting).

Live Mode is a royal pain in the butt in run-and-gun shooting scenarios...in my case, by the time the camera finished "seeking" my subject was long gone.

(Some might say this is why manual focus is the best...but I'd question whether you can focus manually as quickly as you can with Quick Mode?)

Scott

EDIT: One question that popped up while messing around with this was...when shooting in AUTO mode and engaging AE Lock, what is the camera varying to adjust exposure? Shutter? Aperture? ISO? Or all 3? (Anyone know? The camera doesn't "tell you" when you're shooting...) This might be one reason people don't like using AUTO...but again, for run-and-gun situations I can live with it!

EDIT2: Okay, I answered the previous question—kinda obvious I guess—when adjusting exposure in AUTO mode, the camera tweaks any or all of the 3 variables (shutter, aperture, ISO) according to what it thinks best. Like I said, in a run-and-gun situation, that's fine with me.

Well,

For me, there is no such thing as never. But there is a strong need to understand your tool, how it works, and why you may or may not want to do things.

In your case, you asked (then self-answered) a hugely important question. And that was, when set to auto, what is the camera adjusting. A change in ISO might not seem a big deal. Until your work is on a 40 foot screen where the change in grain structure is clearly in view for all to see. A change in aperture might not seem like a big deal. Until details in the background that you worked hard to make sure were invisible through careful selection of aperture, suddenly became plain as day. For example, a logo that you're not authorized to have on screen. That can make a shot unusable in some scenarios. Or a change in shutter speed, that can easily change in-camera motion. Not a big deal in an interview, but could be a VERY big deal if you're filming a chase, or you're tracking on a dolly with the camera and suddenly the temporal motion changes when a cloud comes over.

In a run and gun scenario, you aren't crafting shots, and certain compromises are more than ok to employ, as you've nicely pointed out. But some of those same compromises would ruin things in a more carefully crafted scenario, so more care needs to be taken, and more control needs to be exerted over the shot.

Additionally, in terms of focus, many of us don't work with auto-focus lenses. So those options are not available to us.. nor do we want them. I still remember when we called auto-focus, auto-missed-focus. Some of that is still true today.