DSLR Audio

[magillagorilla]

OK folks, here is a problem I can't seems to figure out without buying a $200 beachtech mic amp/mixer.

I have a Nikon D7000 I often shoot video with. When I'm shooting something special I generally use my Zoom H2 as an external audio source. I later synch the audio and video in VMS. This technique works very well.

However, I would like some options with recording the audio directly to the camera. The problem is, as you may or may not know, most DSLRs have no audio meter. My Zoom H2 has an audio meter, I can use the H2 as a passthrough, but thet tells me nothing about what the camera's audio levels are. There is no headphone jack on the camera for me to monitor the sound. And the camera has 4 gain settings; high, medium, low and auto.

So when I plug the H2 in to the camera's mic jack I have to use the H2's headphone out as my output. This means I have the mic gain to set (on the H2) but then I also have to get the "volume" on the headphone output correct as to not overload the mic on the camera. All this, blind, because I have no real idea how the sound is on the camera.

My tests have been a disaster. Setting the camera to auto gain seems to work a little better, but does not sound as good as using the H2 as a standalone.

I also have an old Sony ECM-717 stero mic I would like to try. I know it's not a good mic but it's way better than teh mono mic on teh camera, plus I can clip it to my shirt, away from the camera (thus getting stereo and eliminating the AF noise).

How are you all dealing with audio on your DSLR video?

[budwzr]

The H2 has a "line out".

[magillagorilla]

My H2, if I recall, has a "headphone/line out". It's not a true line level out because it's amplified by the headphone amp. I thought about measuring the voltage on the output, try to see where the 2-3v level is on the "volume setting".

What settings do you use when you plug your H2 directly in to your camera?

[budwzr]

My H2, if I recall, has a "headphone/line out". It's not a true line level out because it's amplified by the headphone amp. I thought about measuring the voltage on the output, try to see where the 2-3v level is on the "volume setting".

What settings do you use when you plug your H2 directly in to your camera?

Oh yeah, I see what you mean.

I have a hotshoe to tripod adapter and I mount the H2 to the camera. I don't hook it up to the mic in on the camera because that's mono. Only good for dialog. For dialog, I use a wired lav mic.

Maybe you can put a Y splitter on the H2 and then you will hear what's actually going into the camera.

[magillagorilla]

"I don't hook it up to the mic in on the camera because that's mono."

The mic in on my Nikon is stereo. I bet yours is too. Also, listening to the sound out of the H2 tells me nothing about how the camera's mic amp is recording the sound. Besides I can tell how the H2 is doing because it has a meter.

I wish Nikon would put a sound level meter in the firmware, sure would make things a lot easier.

The camera has one of those 1/8in A/V outputs. I pluged headphones in to it to see if I could monitor. I got a horrible hum instead of hearing the MIC. I suspect the headphones jack rings were contacting the video contacts instead of the audio ones inside the jack. I have some of those 4 contact 1/8in A/V cables. I may plug one in and see if teh camera is passing audio through the audio leads. That would eb a breakthrough.

[Cornucopia]

Putting an Audio Meter BEFORE the point where you set your gain it pointless. You have no clue about the subsequent gain structure..

It would be like buying a Pre-baked Pizza where you specified EXACTLY how much it should have been pre-baked, and then finished baking it with no instructions as to how much longer it should be baked.

It should be the LAST link in the chain.

However, since you can't really do that with your present equipment (and I looked at your H2 manual to verify this), you'll have to get additional gadget(s) to help you while you "fly blind".

Get a Audio Tone Generator (Horita, Goldmine, Whirlwind, etc) that outputs ~0VU @ std Balanced Mic Level.

Put the Tone generator into the mic inputs, set the level using the meters to 0dB. Set your Monitoring/Output Volume to the HIGHEST level. Plug in to your D7000; set your D7000 to High gain setting.

Record around 1 minute.

Take the resulting file and play it through your reference listening device (PC, stereo, the H2, whatever you use where you know the average levels), and also look at the waveform in an audio editing app on the PC. Get a reading of the peak level recorded.

Is there clipping/distortion? Then back off the D7000 setting to Med, and then to Low. Repeat.

DO NOT USE AUTO.

If this is still too high, drop down 1 level setting on your volume output of the H2 (and bring back the D7000 gain) and repeat all over again...

Do this until you know where the clipping point is for a Sine wave. Then keep backing off until you have an "average operating level".

Then bring it back to your clipping point and adjust your H2 input sensitivity to where the sine tone matches the "average operating level".

For most pro audio engineers this is ~ -24 to -18dB from full-scale digital. For many video people, it tends to be -15 to -12 dB.

That's where you set your 2 levels (the H2 monitor/output volume & the D7000 gain), and you KEEP them there every time. Then you can at least have a little faith in those meters.

Ultimately, you would probably want to do a complete grid of all possible combinations of levels, so that you see where the least amount of noise buildup occurs with the optimum output level prior to clipping, but that takes a lot of analysis, and it's easier just to use a double system or get a better workflow going with better (read: more appropriate pro) equipment.

Scott

[magillagorilla]

Cornucopia thanks for that "sound" advise.

I know monitoring the direct output of the H2 would in no way help me know what the camera is recording.

"DO NOT USE AUTO" you are correct there. Auto levels are evil. I've been recording sound for a long time and avoid any Auto crap. My experience is in live concert recording, both audiance and soundboard. On blind recording, I always lean towards undersaturated. You can always boost quiet sound, but you can't fix brickwalls. Though too quiet can be just as bad.

I guess it does come down to trial and error. I will get more fancy and dump my audio test tracks to Sound Forge so I can look at them. I would like to center my target on the LOW gain setting on the D7000. That way I am not relying on the mic amp on the camera, which may add yet another level of color/distortion to the sound.

It's tough because I'm working with 3 gain adgustments and I can't monitor. I'm willing to try to work it out because I can't afford any hardware right now and I have a couple of big shoots coming up.

The one advantage of using the H2 as a "plug in" mic is that I can simultaneously record on the H2. So if my sound is bad on the camera file, I can fall back on the H2 recording. This will be good insurance. If I get the levels correct on the camera, I won't have to mess with synchronizing the files post production.

Meanwhile, I have my eye on a few mic pre amps and mics. This outfit makes some really cool stuff http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?category=0 I have no affiliation.

[Cornucopia]

One thing I forgot to mention, and should:

Your manual doesn't specify whether features such as LowPass Filter, Limiter, etc are applied to PASS-THROUGH elements, or whether they're only applied to Recorded elements, so you'll have to also do some experiments with those to see if there's any change.

If there is, my suggestion is to keep them TURNED OFF. They will make your carefully constructed house of Metering cards fall apart.

Scott

[budwzr]

So the BL is basically just test it at different settings, right?

[Cornucopia]

Yeah, I think so.

...BL???

Scott

[budwzr]

"Bottom Line".

Also, the H2 records such great audio that I think it's going to get downgraded by the camera's analog input. Like if you try to record from a sound card headphone jack. That signal is analog.

[magillagorilla]

budwzr you are correct. I too doubt the sound from the H2 "line out" is going to sound as good as the files recorded directly to the H2's card. I guess I have 2 goals; the ability to do quick and easy shoots with minimum post production hastle and to have a redundant audio (Camera and H2), as a insurance.

Why not take advantage of the DSLR's stereo mic input if I'm using the H2 anyway? There is no reason to allow the camera to use it's crappy internal mono mic if all I need to do is run a patch cord.

On special shoots, I can have redundant audio. But for junk like, my kids at the park, where I just want to get some casual footage, it would be nice to not hastle with loading and synching 2 sources in my NLE.

The bottom like is that the camera's mono mic is unacceptable.

[budwzr]

Yeah, that mono mic sux. I have a cheapee Lumix FZ35, and it records stereo, and sounds pretty good too, but the mics are cheap and the dynamic range is subpar.

The H2 has incredible clarity too. I recorded this "waterfall" : Waterfall - Copy.wav

[Cornucopia]

Hey!

That "waterfall" made my wife have to get up and run to the restroom.

Scott

[budwzr]

I have some better ones called "logs falling in lake", and "frogs croaking in a BIG sewer pipe"

[magillagorilla]

I'm glad you omited the video portion of that sample.