Gear Talk > EOS Bodies - For Video

Grinding sound with the T3i

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--- Quote from: paul13walnut5 on September 07, 2012, 10:09:46 AM --- It reads as if you are saying that even if the camera is set to manual audio levels there is still automatic gain?

--- End quote ---

Yes, the automatic gain is still there.
Record a video with the T3i and listen- you'll hear plenty of noise, even if you set the recording level to manual. sums it up:
"Abbreviated as AGC, automatic gain control is a circuit found on some electronic devices that automatically controls the gain of a signal. Using AGC means that weaker signals receive more gain and stronger signals receive less gain or none at all."
Which results in noise caused by the AGC overcompensating.

This forum provides more insight on the subject:

This may not be the problem the user was experiencing, but putting this information out there may help others.

pete vella:
is image stabilizer on is so try turning it off.

I've been meaning to post this for a while but haven't because I don't go on this site very often.
I posted earlier that attaching a microphone to the camera (T3i) will remove the AGC. This is not correct (ML -for T3i-cannot either change the AGC yet).
But I did find this. I tried it and it works very well.

(copied from the second post in the thread, from user jordy2324)

"If you're using an external recorder (such as a Rode Videomic Pro) make sure to send a hot signal (that will be something like a +db swith or a +20db switch) to your camera. Then, adjust the audio levels on your Canon DSLR almost all the way to the left, meaning turning them a few notches from being off.
By sending a hot (high) signal from your external mic to a low gain level on your DSLR, you're avoiding the aforementioned [junky] camera preamps as much as possible. In my experience with the 60D and Rode VideoMic Pro, you can actually get FANTASTIC sound this way. On par with the Zoom H4N."

Don Haines:

--- Quote from: lifilmmaker on September 02, 2012, 08:23:30 PM ---Has anyone ever experienced a grinding sound when shooting video with the T3i?

--- End quote ---
I have shot video with the 60D and the 5DII. On both cameras you can hear the IS. My solution is to turn off IS if using the internal mic, or the better solution, get an external mic. Just about any external mike will beat the in-camera mic. The key thing to look for is some form of isolation from the mic stand, or if hotshoe mounted, from the camera body. The lower picture shows details of a hotshoe mount... the green line points to the hotshoe mount, the red lines point to the elastics used to isolate the microphone from the mount, and the blue lines point to hair shed by Fluffy the cat. (cat hair is optional).


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