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Old June 30th, 2007, 10:05 PM   #1
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Proper Camera Level

I use a Sound Devices 302 mixer. I leave the 302 limiters on.

With the 302's "Level" function active, is it proper to set the levels on a camera to -20dB or -12dB?

With the 302 limiters on, is 12 db of headroom typically sufficient?

If it matters, I typically use an XL H1 but have used many other cameras on various shoots.
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Old July 1st, 2007, 03:25 AM   #2
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You should do a Full Scale Tone calibration to the recording device (camera) and then lock off the gain control on it (the camera). Then, the only way for the recording device to clip is if the 302 clips. It's then safe to ignore metering on the recording device and use your mixer to set the correct level for the scene.

Check page 21 of the 302 manual.

HTH.
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Old July 1st, 2007, 06:54 AM   #3
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Dear Mike,

Thank you. Your reference to Page 21 was very helpful.
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Old July 1st, 2007, 12:28 PM   #4
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I understand Mike's and Sound Devices' recommendation to use “Full Scale Tone Calibration” and ensure that the 302 limiters are on. In this process the camera levels are set to just below clipping. I see advantages to this practice as it optimizes the levels on the camera.

However, I would like input from others, as I am under the impression that many turn on the 302's tone and then set the camera levels to -20dB or -12db giving more headroom on the camera or recording device, but lowers the overall levels.

Considering that Mike's recommendation appears to optimize the recording levels in the camera, why do others set the levels to -20dB or -12dB?

What is considered "Best Practice"?
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Old July 1st, 2007, 12:46 PM   #5
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Hi Dan:

If you compare a sine wave with the complex waveforms of real program material, the peaks of the complex waveform can hit 12 to 16 dB or more higher. So if you set a 0VU sinewave tone to hit -18 to -20dBFS on the camera or recorder's peak reading meters, the peaks on "normal" program material will usually be hitting somewhere up around -8 to -4 dBFS, but meters don't respond fast enough for you to see it. An actors yelling could push it up close to 0dBFS. So the idea is to set 0dBVU tone to -20dBFS and engage the mixer's limiters to kick in somewhere around +18dBVU. Adjust the mixer's input faders so that average program material hovers around 0VU on the mixer's meters and you'll be recording with maximum headroom with a few dB safety margin to insure against clipping, with the limiters kicking in if any peaks threaten to throw you over the line.
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Last edited by Steve House; July 1st, 2007 at 02:16 PM.
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Old July 1st, 2007, 05:57 PM   #6
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Dear Steve,

Happy Birthday! (Sorry but I do not know the exact date).

Thanks for the explanation.

I use the "Peak Level (PPM) + Average Levels (VU)" metering option on the 302.

I had assumed that the "Peak Level (PPM)" metering was accuate and the true peaks, regardless of the signal waveform.

I have been setting the camera's levels to -12dB.

It does seem that the industry standard is -20dB.

I was a little surprised that Sound Devices recommends close to the clipping level, which I interpret to be close to 0 dB.

Steve, I appreciate your advice and hope you have a wonderful birthday.
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Old July 1st, 2007, 07:21 PM   #7
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This may seem like a simple thing, but in fact there is no single industry standard. Each sound engineer is charged with getting a good recording, no overload distortion, reasonable gain above noise floor. Since it is possible to set -20, -18, -12 or even 0db = 0db, different engineers have different preferences as to how they work.

Setting to an industry standard does not guarantee good recording level, therefore, such a standard is not very helpful.

I'll set to somewhere between -6 and -18db, depending on the nature of the performance. Eg, many acoustic music performances won't get louder than a certain level, so, I'm comfortable with less headroom in favor of more gain above noise. A scene where someone might or might not yell; -18db, and so on.
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Old July 2nd, 2007, 12:53 AM   #8
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SD302 full scale test tone is what the name implies, the mixer can not send out any higher levels. Thus setting the camera levels anything lower than just shy of clipping with this test signal is not going to give any more headroom or safety, just waste 12 or 20 dB of perfectly usable space and raise noise leves correspondingly.

Use peak & average reading setting and limiters in SD302, set camera level with SD302 full scale test signal to just shy of clipping the camera and set all audio levels with SD302 after that.
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Old July 2nd, 2007, 02:49 AM   #9
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Quote:
Originally Posted by Dan Keaton View Post
Dear Steve,

Happy Birthday! (Sorry but I do not know the exact date).

Thanks for the explanation.

I use the "Peak Level (PPM) + Average Levels (VU)" metering option on the 302.

I had assumed that the "Peak Level (PPM)" metering was accuate and the true peaks, regardless of the signal waveform.

I have been setting the camera's levels to -12dB.

It does seem that the industry standard is -20dB.

I was a little surprised that Sound Devices recommends close to the clipping level, which I interpret to be close to 0 dB.

Steve, I appreciate your advice and hope you have a wonderful birthday.
They are accurate but don't respond to peaks that are only one or a few cycles in length.

Maximum output of the mixer is around +20 to +22 dBU and I believe that's the level at which it sends tone when you use the full-scale test tone option. So using the full scale tone test to set the recorder's meters to their clipping point, ie full-scale or 0dBFS, should result in a normal 0dBU tone that reads 0VU on the mixer hitting -20dBFS on the recorder.

Thanks for the birthday wishes - my wife and I share the festivities just 4 days apart and this year we have made it a joint celebration with family in Germany for the last 10 days. Currently in beautiful Bad Nauheim.
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Old July 2nd, 2007, 08:58 AM   #10
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This question seems to be about whether -12 or -20 is the best reference level. On professional cameras, I believe -20 is standard, but they also have better preamps. On prosumer cameras -12 seems to be common because you need a pretty hot signal to get decent sound. We use -12 as the reference and set the limiter at 8. That leaves 4 dB of overshoot which is essential with the 302 in my opinion. Set like that though, you really need someone actively mixing because it's just not enough headroom. I'm actually thinking about switching to a -20 reference level (limiter set at 16) for that reason. Wouldn't mind seeing a show of hands on what other people are doing.
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Old July 2nd, 2007, 10:36 AM   #11
 
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ATSC spec is -20dBFS.
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Old July 2nd, 2007, 10:55 AM   #12
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Quote:
Originally Posted by Marco Leavitt View Post
This question seems to be about whether -12 or -20 is the best reference level. On professional cameras, I believe -20 is standard, but they also have better preamps. On prosumer cameras -12 seems to be common because you need a pretty hot signal to get decent sound. We use -12 as the reference and set the limiter at 8. That leaves 4 dB of overshoot which is essential with the 302 in my opinion. Set like that though, you really need someone actively mixing because it's just not enough headroom. I'm actually thinking about switching to a -20 reference level (limiter set at 16) for that reason. Wouldn't mind seeing a show of hands on what other people are doing.
Marco,

That's exactly what I'm using with the SD 442. I tried setting the limiter threshold higher, but the leading edge of quick sounds like claps and some laughs are too fast for the limiter. They sneak through.

Three-ring binders clacking open and closed still get through even with the limiter threshold set at +16. Not that a flat-topped click here or there is a deal killer. I'd rather have one then back the level off and be down in the noise.

Regards,

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Old July 2nd, 2007, 10:56 AM   #13
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Quote:
Originally Posted by Marco Leavitt View Post
This question seems to be about whether -12 or -20 is the best reference level. On professional cameras, I believe -20 is standard, but they also have better preamps. On prosumer cameras -12 seems to be common because you need a pretty hot signal to get decent sound. We use -12 as the reference and set the limiter at 8. That leaves 4 dB of overshoot which is essential with the 302 in my opinion. Set like that though, you really need someone actively mixing because it's just not enough headroom. I'm actually thinking about switching to a -20 reference level (limiter set at 16) for that reason. Wouldn't mind seeing a show of hands on what other people are doing.
Marco,

-20 for tone. That's exactly what I'm using with the SD 442. I tried setting the limiter threshold higher, but the leading edge of quick sounds like claps and some laughs are too fast for the limiter. They sneak through.

The SD limiter is pretty nice sounding; not like the old Shures.

Three-ring binders clacking open and closed still get through even with the limiter threshold set at +16. Not that a flat-topped click here or there is a deal killer. I'd rather have one then back the level off and be down in the noise.

Regards,

Ty Ford
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Old July 2nd, 2007, 11:11 AM   #14
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Quote:
Originally Posted by Dan Keaton View Post
I use a Sound Devices 302 mixer. I leave the 302 limiters on.

With the 302's "Level" function active, is it proper to set the levels on a camera to -20dB or -12dB?

With the 302 limiters on, is 12 db of headroom typically sufficient?...
I prefer -12 as a reference for most digital recordings w/ the limiters engaged. For me, the only exception would be when capturing a abnormally wide dynamic range scenario.

In a non limiter situation, the lower recording reference level is a safer way to go.

-12 is a good place to start when you want the ability to lower the recording in your mix or add a mild compression.
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