I just tested the audio performance of the Korg MR-2, so figured I would run similar tests of the Canon 5D-MkIII to see if there’s any need to use an external recorder.
I sent clean (very low noise) audio from a Woo Audio WA-7 into the Canon via a shielded Monster cable. I swept the audio volume slowly at three mic level settings.
At the lowest possible setting, one click up from muted, the recorded audio exhibits slight noise when amplified by 30 dB.
With the mic set at the first marker, a quarter of the way up, there’s a little noise even with just 18 dB of amplification.
With the mic set at the second marker, half way up, there’s noise lots of hissing with 12 dB of amplification.
This shows that the onboard amp and ADC are fairly noisy.
I also ran a test in which I set the audio levels to the target green mark 2/3 of the way up the scale, at which point the indicator bars go from white to yellow. I found that’s -12 dB from clipping. And about 1/3 of the way up results in -24 dB recording.
The Canon’s recording circuitry is noisy, so it is best to use the +20 dB boost on your external mic if possible. Don’t be afraid to set the mic levels very low on the Canon, it performs best at the lowest possible setting. But also try to set it so the recording level is near the -12 dB green indicator, occasionally going into the yellow. On the Canon, if the recording does clip, it doesn’t sound harsh because there’s some kind of compression onboard. I guess that’s necessary when the noise floor is so close. Also, the next post will show that the frequency response begins to drop off below 150 Hz, so you will get poor bass performance. Use an external recorder along with your external mic, if possible.