0. Is there any way (either on camera or in the OES Utilitry) to have the live view window NOT time out after 20 seconds?
1. The focus box that shows a zoom view will not go down to the edges of the screen. Is this changeable?
2. Because of the timeout (I think) the work to take one picture is something like this (shoowing in Manual, tethered to a Mac):
take the shot
wait for the shot to be saved
hover over the shutter button to extend the live view window
click someplace on the live view window
clock on the focus change button (> or >>)
move back to the shutter button and take the picture
If i move the zoom window the screen may go
Sometimes I can tell that the focus has been changed because I hear a little whirr from the motor, but sometimes not. Id I'm not using the zoom window (because I'm concerned with the periphery of the frame) I can't always tell if the focus has changed. am I missing some obvious signal
3. If the camera is in Av mode, the live view window doed not go dark -- this seems to happen only with M mode. Is there an understandable reason for this?
For your first question... you can set the camera auto-power off time-out period. I think it defaults to 30 seconds but you can set it all the way up to 30 minutes... or even "never" (not a good choice unless the camera is running on the AC adapter.)
My astrophotography camera is usually set to 30-mins or "never" (it does run on the AC adapter) only because I'll set it up to start capturing images and let it go for hours (and just walk away while it does it's thing.) But that's not a common way of using a camera so most people are happy with the default 30 second timeout.
I don't have a T3i, so I can't tell you where it is on the menu navigation. But _every_ Canon camera I've used from my T1i through my 5D III has this setting.
Here are a few additional thoughts. I am checking these things out on a T5i, so there might be some differences.
1. the power off timer only comes into play if you are not doing something with the camera. As long as you are adjusting focus, adjusting exposure, etc. the time out is defered.
2. in Live View there is a metering timer that is adjustable from 4 sec. to 30 minutes. I haven't tested, but I would suspect that would override power off timer.
3. depending on lighting conditions and camera setting, Manual mode in LiveView can turn dark compared to Av becuase the camera won't make any adjustments automatically. In Av the aperture, and depening on your ISO setting (i.e AUTO ISO) even the ISO will change.
4. In LiveView FlexiZone Focus if I select the magnifying lass button I get 5X or 10X magnification. I can move the focus mark using the four buttons around the SET button - i.e. WB, AF, (Picture Style icon) and (drive mode icon).