You may want to light up that camera first and ensure you'll get what you think you're going to out of it, and for as long as you need it to be outputting. I don't think you'll have much luck getting your T3i to output video for the length of an entire service, at least not reliably.
DSLR's fall into something of a weird
category involving European Union tax code that allow them only to record up to ~30min. Beyond that, they would be considered video cameras which are taxed at a higher rate than still cameras. Long-story short, they are not designed nor intended to be long-duration video sources. I know with my Canon 60D, even if I'm just using the output for
preview and not recording, eventually the sensor will heat up too much and stop outputting video until it cools down. If I'm recording, I might make it to the tail end of my first 20 or 25-min clip just fine, but 15min into the 2nd clip it might
drop out on me. That's just not what these cameras are designed for.
I would also avoid using the built-in mic. You really want to pull direct audio off of a
mixer or a mic and use an
HDMI audio embedder to insert it into the camera feed. The camera's mic will
pick up a lot more coughing, rustling of hymnals, opening of cough drops, so and general room noise. It may also require so much
gain that your hear a significant amount of digital noise whenever you turn it up loud enough that you can actually hear the worship leader's voice.
Also consider that the T3i doesn't have any AGC (Auto
Gain Compensation). It will not automatically adjust to raise the audio
gain during quieter parts or lower the
level of louder moments. It's not a "set-it-and-forget-it" type of device.
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Overall, I'd question how much you really need video in the nursery. It will largely depend on the types of services you have, the expectations of your parishioners, and your budget. It's probably much more cost-effective and frustration-free to
drop a handful of 70V ceiling speakers in that space with a volume control on the wall,
fed by a 70V
power amplifier driven from an extra output of your audio
console or
DSP. Unless you have more of a contemporary style of service, hearing what someone is saying is more important than seeing them say it.
Video in houses of worship is a lot like climate change. A growing insurgency of people can agree that it will become increasingly important, but nobody can agree on if or why they need to do something about it or how much they're willing to spend on resolving it. Nobody has
clear expectations on what can reasonably be done about it, and the people who've "figured it out" are spending an obscenely higher amount of money on it than anyone would reasonably expect.
If you decide you do really need video in there, I would go through these questions and do a little soul-searching:
1) What is your budget?
2) Will this only ever be for the nursery?
3) Are you okay with it looking a little like a security camera?
4) Are you ever going to need to add different camera angles and multiple cameras?
5) Are you ever going to record your services?
6) Do you want your recordings to look as good as the other houses of worship in the area?
7) Are you able to reliably have a camera operator every single service or do you need it to completely turn-key -- just on/off from a couple
power buttons and that's it?
8) How much labor is involved it you need to open up some ceilings and string some extra cables out between where your camera and
mixer live and where your nursery and any other overflow-type spaces are?
9) Are there people in the nursery for long segments of the service for whom it would be a fundamentally different experience hearing the service as opposed to seeing it?