06-12-2013 02:56 AM
In Automatic Mode (A) and if the lighting is low, the flash comes on automatically, a green box is provided when ready to expose and I then fully depress the shutter button. Sometimes though, I get a red box and cannot take the picture. It is a bother not knowing why or how to correct it. I end up having to relocate and being denied the original view I selected.
06-12-2013 05:50 AM
06-19-2013 09:00 PM
06-20-2013 07:44 PM
By default the camera is in "One Shot" mode -- but you can change it to "AI Servo" mode.
In "One Shot" mode, the camera will focus (or at least attempt to focus) and ONLY after it is able to confirm focus will it take the shot. This behavior is known as "focus priority".
In "AI Servo" mode, the camera will continuously re-evaluate focus. This mode is intended for moving subjects where the focused distance is constantly changing. However... one nuance of this mode is that if you DO fully press the shutter button, then the camera WILL take the shot -- whether focus was able to be locked on any subject or not. This behavior is known as "release priority".
On Canon's mid and pro level bodies you can over-ride this behavior (e.g. you could use, say, "One Shot" mode, but still set it for release priority.) On Rebel bodies such as your T3i you cannot override the mode.
Unrelated to your question, the "red box" / "green box" tells us that you're using "live view" when shooting. If you haven't done so, you may want to become familiar with using the viewfinder instead of live view. There area lot of advantages to using the viewfinder over live-view mode. One of those advantages (there are many) is that the camera focuses much faster -- which would be important if you're shooting anything with action.
06-20-2013 08:35 PM
I was wondering about that, but not too familiar with Live View. It's possible if you're in Live View that it's not using focus assist?
+1 on TCampbells suggestion to try using the view finder... it's why you have a SLR