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Canon 5D MkIII - recording 2 audio channels?

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Grant Peacock
Canon 5D MkIII - recording 2 audio channels?
on Jun 27, 2016 at 7:27:53 pm
Last Edited By Grant Peacock on Jun 27, 2016 at 7:31:41 pm

Our shop would normally only tackle a documentary day with our C300's, but a (new) foreign client insisted we film an interview yesterday with two 5D MkIII's (doc in progress with this platform; we're just adding to the show).

I got my bum kicked as a result of going ahead with this camera (conscientious people do suffer).

We had 2 issues with these cameras (identical models) -

a. both of them locked up at about the same time (I'm researching multiple possible causes of that - both had been running for about an hour at the time - overheating, undocumented incompatibility with certain CF cards, other unknown issues - even some chatter about motherboards being changed out by Canon in some of the earlier units).

b. We could NOT figure out how to get a 2nd mic signal into the camera. I would have liked to send boom and lav to both cameras, knowing that audio into these cameras is a tricky prospect to begin with (we quietly recorded our own WAV files, just in case we get some feedback from the client about audio into the cameras). Again, client's insistence that this is the way they would continue to work on this doc (ech).

Even prior to the day, during setup of both cameras, I could not find an answer to this audio input issue online nor in docs. The consensus from audio pros seem to be that the preamps are still not great quality in the gen 3 of this camera, but I was also seeing enough feedback that feeding a line-level signal into the camera was not advisable (presumed aim being to run those preamps as minimally as possible). We ended up passing our 2 channels through our Zoom F8 at mic level, with post-fade levels set so that the 5D's were doing well at about -12dB showing on their metering. We've checked the results in our own system and they are fine.

What we cannot figure out is why that 2nd channel just won't register inside the camera. The 1st channel showed up where it was expected, confined to one side, and all was good with that. Swapping out stereo mini-cables, etc made no difference (we also verified the SUB OUT from the Zoom F8 to make sure that we had 2 discrete channels on the output jack there).

Any thoughts? We turned out to be okay with a single overhead boom, but we could have easily been in a 2-mic situation, without any way to get them both onto the CF cards. Nothing in the 5D's menus seems to be relevant to this issue.

Cheers, recovering here, and hoping not to be come a '5D doc specialist'. Yesterday probably helped originate a few new gray hairs.

Grant.

Grant Peacock
Washington DC
GPI TV LLC

http://www.gpi.tv


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Al Bergstein
Re: Canon 5D MkIII - recording 2 audio channels?
on Jun 28, 2016 at 3:08:15 pm

Grant, if I needed to do what you were looking to do, I'd use my Sound Devices Mixpre-D. I don't know of any problem in bringing in a stereo signal to the MKiii, as you can buy a stereo mic from Rode, for example, and it works fine.

To be clear, normally I see the audio meter on the bottom of the screen showing two channels of audio coming in. (the meter has an upper and lower register to it). With a stereo mic, the meter should be showing the upper and lower split, just like your C300 does when you run two mics into it, or use an external feed and the camera mic.

I just thought I would check so I set up my Mixpre-D (with it's special cable which has a dual tip (two blacks) on it. I plugged in one shotgun mic through it and the Canon definitely shows one channel of sound coming in.

If you were using standard Rode like mics that attach to the top of the unit, there is a stereo pair adapter I got from B&H. I can't remember the manufacturer, but the unit has a B on it. On the front is two knobs for L & R, the back has three small inputs for standard camera mounted mics, and one output. With it I can dial in volume from each mic.

Either setup allows me to do two mics and the Canon shows stereo channel input. Once in my editor, I can split the two channels out into dual mono or use only one with the best feed.

Does that help?

Al


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Al Bergstein
Re: Canon 5D MkIII - recording 2 audio channels?
on Jun 28, 2016 at 3:12:58 pm

By the way, the pre-amps in the Mkiii are not great but they are fine. I've done a lot of interviews with them, and they are vastly better than the previous one. I actually challenged the audio gurus on Cow (I spend time listening to them, as they have great ideas and a lot of experience) and they admitted that the pre-amps in my interview were fine.

This is one that was shot on the 5Dmkiii with a single lav mic. I thought it was fine, and doubt my C100 would do any better, or just recording it to a separate recorder.



All the best.

Al


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Grant Peacock
Re: Canon 5D MkIII - recording 2 audio channels?
on Jun 28, 2016 at 9:01:54 pm

Thanks Al. The feedback you've given confirms that the camera should not have a problem recording 2 channels of audio, but so far I have not learned anything to figure out why these 2 units would not respond in the same as yours does.

You've affirmed that when you properly feed 2 channels, by what I also assume is a 3.5 mm stereo mini-plug, you are able to see and record L and R audio channels. We continue to see only one audio channel going to each camera.

In any case, the project is delivered, and if we hear nothing further, this might be one of those issues that just can't be solved without shipping the cameras across the country. We don't see ourselves relying on the 5D's for 'principal photography' again any time soon.

I don't normally move unbalanced signals around between pieces of gear, and so I have this nagging feeling I'm missing something here (XLR cabling is the defacto for us).

Thanks again Al.

Grant.

Grant Peacock
Washington DC
GPI TV LLC

http://www.gpi.tv


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Al Bergstein
Re: Canon 5D MkIII - recording 2 audio channels?
on Jun 28, 2016 at 11:29:11 pm

Yes, I feel I'm missing some key element in your setup that I probably could understand if I was standing in front of it. Mixpre-D does specify a special cable that B&H sells for the unit. And yes, just like on a C100/300 I could see two differing audio levels in my camera.

In reading your post, I'm making some assumptions, one of which is that you are using the right kind of 3.5 cables coming in, which you seem to say you did use. (the stereo 3.5s and not mono). I have a Zoom H5 so I don't know if you made an error setting up the Zoom.

I've loved the Mixpre-D as it does allow XLR mics to be piped into a 3.5" jack with no issues for me.

As to the lock ups, yes, an hour in summer heat could do that to them. They are not setup with fans like the C300s. Not designed to be run as video cameras for that length of time. I've never had it lock up but I know of others that have. I feel that they were designed for short clips.

Glad it all worked out.

All the best.

Al


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Al Bergstein
Re: Canon 5D MkIII - recording 2 audio channels?
on Jun 29, 2016 at 6:07:57 pm

I love a puzzle and think I solved this one. I could not understand why your Canon was seeing two channels linked together when it was a mono input. So here's what I think was the problem, for use next time.

When I hooked up a shotgun xlr mic to my mixpre-d, the output to the Canon was mono, one channel only, and it switched from left to right as I moved the mic from l to right inputs on the Mixpre. I was using the specific cable that is sold for the Mixpre-D to 3.5" jack.

I then hooked up my Zoom H5 plugged in the same xlr mic, using the standard 3.5" cable I always use, (also has two black rings on it as does the cable from the Mixpre), at first, I was getting both channels out together as a mono pair, as you described. However, when I went to the "recording" menu on the Zoom, and made sure that the setting was Stereo and not Multifile, the recorder treated the single channel as a single channel on both the Zoom and the line out to the Canon.

So make sure your Zoom is recording Stereo, you should be able to hear the mic in the appropriate channel and the levels will show the appropriate channel on the Zoom, and on your Canon. It seems that the Zoom line out is driving quite hot, as I had to pad my output or lower the recording volume to a very low level on the Zoom not to overdrive the Mkiii. Not so on the output from the Mixpre-d.

Hope this helps your next job.

Al


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