How bad is AGC?

J

Jean Dantes

Well-known member
Just wondering how bad AGC will be for those of us that wish to attach a microphone to the 7D, but cannot afford the likes of a H4N (plus that thing that sends a silent audio signal to the cam that "kills" the AGC)?

Are there any microphones with headphone inputs? Or is the H4N the only one on the market so far?

Thanks in advance to any replies :)
 
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Microphones don't have headphone jacks. That's nonsensical. A microphone's sole job is to collect sound waves and convert them into electrical signals. So a microphone, in and of itself, doesn't even record sound. I suppose that you could get a splitter for a microphone so that you can attach one branch to a recorder and another branch to headphones, but that's a nasty idea, because the splitter will cut the volume in half.

The H4n is merely a portable sound recorder. It's a well-designed, feature-packed one at a great price, which is why it's popular. Other portable sound recorders provide the same core functionality (built-in microphone, recording to digital files, headphone and LCD monitoring). You can easily find a decent portable sound recorder for $100-150 USD. I have the Tascam DR-07, for example.
 
you could also try the cheaper zoom, the H2... it's about 2/3rds of the price. looks smaller too, but I'm not sure how much... i've got the H4N but was very interested in the H2 except it doesn't have xlr inputs... the H4N is very chunky, wish it was smaller
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  • Recording Format: [Stereo mode]
  • WAV(Quantization:16/24bit,
  • Sampling frequency: 44.1kHz), [4ch mode] WAV(Quantization:16/24bit,
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  • WAV(Quantization: 16/24bit,
  • Sampling frequency: 44.1/48/96kHz), MP3(Bitrate:32/40/48/56/64/80/96/112/128/160/192/224/256/320kbps/VB Sampling frequency:44.1/48kHz), [4ch mode] WAV(Quantization:16/24bit, Sampling frequency:44.1/48kHz) Display:128x64 pixel,back-lit LCD
  • Inputs: [LINE IN] 1/8" stereo phone jack(Input impedance:10kΩ, Input level:-10dBm), [EXT MIC IN] 1/8" stereo phone jack(Plug-in powered:2.5V, Input impedance:20kΩ, Input level:-20/-30/-40dBm), [Built-in stereo mic] W-XY stereo microphone(MIC GAIN:+1.5/+17/+27dB)
  • Output: [PHONES/LINE OUT] 1/8" stereo phone jack([LINE] Output load impedance:10kΩ or more, Rated output level:-10dBm / [PHONES] 15mW+15mW, into 32Ω load)
  • USB Interface: Mini-B type(USB2.0 Full-Speed compatible), Mass Storage Class operation / Audio Interface operation(16bit, 44.1/48kHz)
  • Power Requirements: AA size(LR6) battery x2, or Supplied AC adaptor AD-0006(DC9V/300mA/center minus type) ? Battery Life(with alkaline batteries):4 hours recording, 4.5 hours playback Dimensions:63.5(W)x110(D)x32(H)mm ?Weight(without batteries):110g Supplied Accessories:SD memory card(512MB), Desktop stand, Mic clip adaptor, Wind screen, Earbuds, USB cable, Stereo Y cable, AC adaptor(AD-0006)
 
Mics like the rode video mic have 'headphone jacks' meaning to plug into the camera - you cant plug headphones into the mic (or camera) to monitor sound

I would say sound quality is 'adequate'

AGC is basically a gamble

If you have a silent environment it will up the levels incuding hiss and meaning your first noise is too loud

Given some constant ambient it is OK

I tested and found that with the 50mm doing a head interview it is OK whereas with the 28 on a full head (5d lenses) ie 30 and 16 on the 7d, it becomes too attacky

Its usable, but not that cool

S
 
Thanks everyone for the feedback!! Very informative!!! :)

So, let's say that I were to use a H4N, it would still be affected by AGC, right?
 
Nope, you would record audio separately on the H4n and not use the camera's audio at all, except for a syncing reference.
 
Ahhh I see.

So the H4N doesn't override the 7D's audio recording system? And am I correct that the H4N can be attached via the 7D's hotshoe?

Thank you all again!
 
It exists, and it ruins audio tracks by constantly increasing or decreasing the volume. It's the same problem as auto-iris, auto-ISO, and auto-shutter. The biggest problem with it is that you can't turn it off.

It can be a useful feature when you need it, but the inability to disable it relegates any audio recorded with AGC to the amateur pile.
 
Jean Dantes said:
Ahhh I see.

So the H4N doesn't override the 7D's audio recording system? And am I correct that the H4N can be attached via the 7D's hotshoe?

Thank you all again!
Click to expand...
You could wedge it in there, but you don't have to. It's totally separate. It has nothing to do with the 7D. It's a standalone recorder.
 
So this is where a clapper board would come in handy, right? :)

One thing though, and this may sound rather stupid, but if I were to record a video on a 7D at 60FPS, and record the audio via the H4N, would the audio files of the H4N still match up with the audio of the 7D's quicktime file? Is audio always 1:1, regardless of what frame rate you are shooting at?

(Again, sorry if this sounds stupid, hope I made sense lol!)
 
Yes, audio doesn't have a frame rate, it doesn't know or care what frame rate you shot your video at, real time is real time.

BUT -- audio has a sampling rate, and you can get yourself into a little trouble if you use the wrong sampling rate.

Most video editing is done nowadays on a 23.976, 25.000, or 59.94 timeline, at 48000 Hz. If you record your audio at 48000Hz, you should be able to drag it onto your NLE's timeline and use it directly.

Where you can get into trouble is if you're shooting at a different frame rate (such as, for example, the Canon 7D shooting at 30.000 fps). Because your editing timeline will probably be 29.97, but the actual frame rate was 30.000, that means your video will not play back at the true rate it was meant to, and because of that, you'd have to adjust your audio too.

But with a 7D that won't be an issue, since it shoots at video-appropriate frame rates.
 
That's up to you; more bits = better accuracy of recorded audio, definitely. But does your NLE support 24-bit sound sources? If not, you might just be making trouble and taking up 50% more space.

CD audio is 44.1KHz 16-bit, and DAT is 48KHz 16-bit. 16-bit is the size of pretty much all of the professional video formats I can think of, so most NLEs support 16-bit. I haven't even bothered to look if my NLEs support 24-bit because I don't have any 24-bit recorders. Maybe it's already universal?

In any case, you will get better quality, although the amount of improvement really probably depends on what you're recording. Dialogue? I doubt you'll hear much of a difference. A symphony? Definitely go 24-bit if you can.
 
k, tks. I just dropped it back to 16bit. I imagine CS4.1 supports 24bit but all I ever record is dialogue and you're right...makes no sense to double the file size needlessly.
 
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