Setting Audio Trim on Camera...

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How does one work out what the optimal 'Audio Trim' setting on the Camera Input (Menu Item) should be for any particular microphone.

Default is 0dB. Options are -18dB thru +18dB.

I am guessing its a bit trial and error so that the microphone is reading somewhere around '5/6' on the Audio Level Dials in normal recording situation.

Maybe its more scientific based on the mic specs?
 
thats what someone said was "right"(when i once inquired) ...if audio pot is set to halfway, meters should generally read between -20 and -12 for normal dialogue when trim is set correctly for a given mic.
 
The audio level controls should be set so the levels are peaking at the reference point....there is NO way that any gain should be regarded as 'standard'.
For example interviewing a quiet spoken lady in a library will be VASTLY different than a man doing a standup shoot at a football match.
Things that will affect the audio control level will be what sort of mic is used, who is speaking, are a loud or quiet speaking person, noise level at the location etc etc etc.

It would almost be like asking what iris setting should I use for a camera on a shoot?....... Well is it indoor, outdoor, day, night, lights or no lights, sun or shade?

Always monitor with headphones..... not doing it would be like shooting a video without a viewfinder.
 
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He's talking about the TRIM level. . .which is a more "set and forget" setting than the audio pot/dial/channel volume. Usually a menu driven thing. I know I have certain clients with cameras who have never touched that setting or altered it from where it is at from factory setting.
 
With any piece of gear in the manual it will give the instructions of setting the correct audio levels... Often they are different from make to make & model to model.

For example -12 is a 'Hot' signal meter where the reference level is -20..........And exactly right for a recorder with a reference level of -12 and if it has VU meters -12 is WAY to low......so as I mentioned it depends on the make / model of the recorder / camera.

Yes I also know of people who never change settings to suit a shoot, and the results show..... Technology is a learning curve for everybody some people grasp it and others dont. For example computers and mobile phones are a constant changing technology but most people grasp it.

If you have mastered the video side of shooting videos then the audio side of video production is much easier.....
 
I think we're misunderstanding each other. Trim is the input sensitivity, as i understand it, and will be set differently only for different input sources (usually a mic, could be feed from a mixer or pa, etc.). If you were always using the same mic, you probably could leave it alone. And no, leaving it the same does not result in poor audio necessarily--i have worked with much ex1 footage where trim is left alone regardless of mic and if the recording was done properly (setting levels, monitoring) it always turns out fine.
 
I think you are right Josh,

It varies from device to device, but some just have a "level" control, in that case it is going to move around a lot depending on what you are recording.

Some devices and almost all mixers have a "trim" and a "level" for channels as two separate settings. Trim is quite related to the mic and not so much content. You may well adjust it up or down a bit for each specific use but generally it is going to be about the same for the same mic. The level is what is going to be where you make your live adjustments.

To the OP, trim is very related to the mic output. So a dynamic mic will be set a LOT higher than a condenser usually. If you are always using the same mic you should be able to set the trim for it and not have to change it with few exceptions.

One way to set the trim is to have your channel fader at unity and adjust the trim till you get a good strong signal and overloading the mic is a bit below clipping. Where exactly depends on the recorder but if the mic overloads and you are at about-3dB you are about as high on the trim as you can go.

If that lets you get a decent signal for what you are recording you are good.

This is a bit of a weird way to set this and is not always practical. I do a lot of FX recordings so I'm often in situations where the sound might get MUCH louder than expected and where you only have one shot at getting the recording. So I like to make sure I'm safe in my clip points. If what you are doing is not going to have the unexpected explosion , metal crash etc. then you can generally go the more normal route of setting the fader at unity and adjusting the trim till you get a good solid signal. You do have to make sure what you are setting on is close to what will actually be the level when the recording is happening.
 
Josh Bass said:
He's talking about the TRIM level. . .which is a more "set and forget" setting than the audio pot/dial/channel volume. Usually a menu driven thing. I know I have certain clients with cameras who have never touched that setting or altered it from where it is at from factory setting.
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I'm one of them, but I'm beginning to see it's a mistake. Sometimes trim needs to be adjusted to the situation. Not doing that is why my camera audio pots are at 9 most of the time for normal dialog. That means more preamp noise. I need to bump the trim up so pot resides around 6 or 7, assuming no distortion occurs. Preamp noise usually happens above the 3/4 level on most devices, in my experience.
 
I will be doing a little test to establish settings fro my various mics. ( Tests are always a good idea anyway)

Will set up my 3 shot gun mics at same (normal) distance from a 'talking head".

One of the mics sony has recommended 0dB trim setting ( so thats a known).
Will trial and error the rest with the objective that the audio level knob is operating in the 4 to 7 range... for each one.
(I am expecting that the "hot' Senheisser will need -10dB and I wont use the pad cable)

Will mark each mic with a refernce sticker and do the same test with the 4x handheld condenser mics and then do tests with the radio mic system .

When I have a pro recordist in...they set things up the way they wish with their own gear. They dont usually reset it at the end of the shoot.
 
From Noiz - One way to set the trim is to have your channel fader at unity and adjust the trim till you get a good strong signal and overloading the mic is a bit below clipping. Where exactly depends on the recorder but if the mic overloads and you are at about-3dB you are about as high on the trim as you can go.

That's the way I to it for broadcast with talent that comes on/off several times during a show. Before the show, I have the talent talk as though they were on air. I have the fader at 0. I set the trim to where I want the level to be when they are talking. Once that is set, then I use the faders during the show. But sometimes talent decides to talk louder or quieter on the show and then I re-adjust trim.

This is useful when you have a show where the talent comes in and out of a show several times. When they are off air, the fader is down. When it is their turn to be on air, you can set the fader to 0 just a second before they start talking (they like to clear their throat and other ugly things just before talking) with some confidence that it is in a good position when they start talking. Without the trim, you would have to remember at what level each fader needs to be set when the talent comes back on.

[edit] This applies when each talent has their own microphone.
 
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Oh man. The debate of all debates UNITY GAIN MIXING!

While this approach has gained (pun intended) popularity in the last 10 years, it completely disregards proper gain staging thru the mixer. Channel output faders have nothing to do with setting proper channel trim. In fact, most quality mixers have a channel function just for that purpose. It's the PFL momentary switch. Apply input signal to the channel, activate pfl, and adjust trim to proper metering.

Why use this approach?

1. Signal is optimized for any following gain stages and taps, specifically aux and monitor sends and equalization. Each of these circuits are designed to operate a a desired signal level for best signal-to-noise and that all happens before the fader.

2. After trim for each channel is set, fader positions while mixing indicate relative acoustic energy levels of the sources, thereby providing a quick reference in identifying possible spill/bleed sources.

I know many professional sound mixers who use the unity gain, set faders to 0 approach and make it work for them and achieve great results and would struggle to use the approach described above. However, the circuits were designed to be used by establishing proper gain staging beginning with trim/attenuation, and ending with fader, not the other way around.

It's the same argument as recording signals at too low a level and then boosting them in post.

Paul F said:
From Noiz - One way to set the trim is to have your channel fader at unity and adjust the trim till you get a good strong signal and overloading the mic is a bit below clipping. Where exactly depends on the recorder but if the mic overloads and you are at about-3dB you are about as high on the trim as you can go.

That's the way I to it for broadcast with talent that comes on/off several times during a show. Before the show, I have the talent talk as though they were on air. I have the fader at 0. I set the trim to where I want the level to be when they are talking. Once that is set, then I use the faders during the show. But sometimes talent decides to talk louder or quieter on the show and then I re-adjust trim.

This is useful when you have a show where the talent comes in and out of a show several times. When they are off air, the fader is down. When it is their turn to be on air, you can set the fader to 0 just a second before they start talking (they like to clear their throat and other ugly things just before talking) with some confidence that it is in a good position when they start talking. Without the trim, you would have to remember at what level each fader needs to be set when the talent comes back on.

[edit] This applies when each talent has their own microphone.
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yes, but keep in mind we're talking about a menu-based camera setting here. how would you apply your method in that case?
 
While this approach has gained (pun intended) popularity in the last 10 years, it completely disregards proper gain staging thru the mixer. Channel output faders have nothing to do with setting proper channel trim. In fact, most quality mixers have a channel function just for that purpose. It's the PFL momentary switch. Apply input signal to the channel, activate pfl, and adjust trim to proper metering.
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Of course PFL stands for Pre Fader Level, in other words "unity" on the fader. It's the same thing, the whole idea is to take the channel fader level out of the equation. In theory if what is marked as unity actually is then both methods should get you to the same place. And I was trained in on this in the early 70's so a we bit longer than 10 years.

However as someone mentioned above PFL is not an option for the original poster.
 
no. anything over 0 is clipping, unless you're using Sound Devices gear properly. Then you're good to just below +20 on their gear.

And let's be clear that we're talking about PEAK meter readings, not RMS or VU.

Thanks!

Ty Ford
 
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As a side note a very useful way to check gain though an audio chain is to get a tone generator source that can be set to -50dbv and plug it onto the XLR where you would normally plug the mic.

The low cost Behringer CT100 cable tester can be a cost effective way to do this and you can then adjust levels all the way thru a mixer to camera so at least you have a common fixed reference source that is very close to an average mic gain at the front end of things!

As for levels each source may have different scaling but there are plenty of resources on-line to show what they all mean, for the UK it is generally -18dbfs = 0db (4) ppm = -4db VU.

As for peak levels I work in UK broadcast so follow that -10dbfs = +8db (6) ppm = +4db VU is generally my max level although in the USA and other areas -20dbfs is the line up level with -12dbfs being the peak for broadcast.
 
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Good call Gary.

The Sound Devices mixers all have reference level tones built in. I've been on shoots where the camera op has said, "Oh, I already have a tone generator in the camera. I don't need your tone."

I smile and explain that his camera tone won't help me calibrate my mixer to his camera's audio inputs.

That's what the whole thing is about; calibration of the two devices (mixer and camera) so I don't have to look at the camera levels to know what's going on.

Unfortunately, the fun doesn't stop there. There are arguably professional cameras out there that were designed using the -10 dB prosumer line level audio standard. You can certainly calibrate them at -20, but you'll run into clipping at about -10. It took a few YEARS to discover this very weird problem and come up wiht a fix.

My Sound Devices 442 mixer has a 3-way output switch; mic, -10, 0. I always try sending line level out to line level in to the camera because the hotter signal will prevail over rf and other transient noises. (NOT acoustical noises that mics pickup, electrical noises that can get into the cable) When the camera started to clip at -10, I first tried going mic level to mic level. That worked. Next time I ran into the problem I downshifted from line to -10. Problem Solved!

At the heart of the matter is that each of these levels is also described as a voltage. The "prosumer" cameras, even though they used professional XLR connectors, weren't designed to operate at professional level. How silly is that? But that's the deal. I recalibrated the mixer to the camera using the -10 output and had no problems.

Regards,

Ty Ford
 
tyreeford said:
no. anything over 0 is clipping, unless you're using Sound Devices gear properly. Then you're good to just below +20 on their gear.

And let's be clear that we're talking about PEAK meter readings, not RMS or VU.

Thanks!

Ty Ford
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I'm not sure what you are talking about here. Over 0 is not clipping unless you are referring to FS digital. And US metering is generally not peak reading. When folks are talking about dialog living in the -20 - -12 range they are talking about RMS (as almost all US meters read) levels.

Almost all professional gear is capable of going well over 0, but what that means depends on what your reference is. SD uses dBu, not exactly universal.

Some folks have been talking peak, some RMS, and I believe there have been some VU levels mentioned. So I think it's actually confusing for you to say that "we" are talking peak, because clearly some have not been.

However the OP question had to do with trim setting on a camera.
 
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