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A black magic camera with... meters!


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If in doubt ; set tone at max level on your mixer, back off a few dB on camera. That way you know the sound on camera is not much worse than the sound on your mixer.

If your chain contains a wireless system, make sure you have correctly gained those as well. Same procedure; tone at max, back off until the device doesn't clip anymore.

And then save your back by saying "well at least now I know it's not gonna distort and the levels should be okay, this camera is designed with sound in mind so please bear with me"

Then imitate a bear real quick and go shoot the movie

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When I send -12 tone to the BM and line it up to -12 on the meters everything is fine, but then when I turn my tone knob to -6 it does not correspond to -6 on the camera's meter. Instead it is somewhere more like -10. The point being, when I align everything up, the reference tone when changed does not follow the same kind of change on cam meter. It is like we are dealing with two metrics of dBFS. My mixer's meters and the cam meters seem to measure increments of decibels completely differently. 

This is so frustrating because I tried so many times and I don't know what to do next. Thanks in advance. 

 

Thanks everyone for the help and advice so far.

 

This conversation has seemed to evolve into the topic of "general gain staging", which is helpful, but my original question was related to very strange behavior from the black magic production cam meters.

 

The quoted text above explains my problem and if anyone can shed any light onto why these meters behave like this, I would appreciate it!

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I was working with the BM Cinema Camera last year for several weeks for a feature Film. The firmware did not allow for metering at all.

We did try different ways of bringing the audio to the Camera, but gave up in the end. We only used it for reference when syncing in post.

Even with the meters I don't recomment using the cameras audio in for any serious production.

YMMV

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Thanks everyone for the help and advice so far.

This conversation has seemed to evolve into the topic of "general gain staging", which is helpful, but my original question was related to very strange behavior from the black magic production cam meters.

The quoted text above explains my problem and if anyone can shed any light onto why these meters behave like this, I would appreciate it!

The point others were making, I think, is that it doesn't matter. Read JonG's post again, and others and you'll know what to do. The meters on this kind of camera may not be precise at all, the marked reference point may not even be at -12, but maybe somewhere around there. If the Blackmagic guys don't know (or care) how should we? It's always best to not record production audio on the camera. Instead treat it as a scratch track, and suddenly it all becomes less relevant
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  • 2 weeks later...

I was sing the BMPCC with the Rode Stereo MicX and was quite impressed by the sound quality. This on camera mic is prone to humidity humm / buzz (worst than Schoeps) but has overall a nice sound (sorry not very professional comment). But fine tuning the metering is critical if you think the camera mic is also important.

 

I've set the mic preamp to +20 and the input mic at 35% on the camera. This setting with that mic is usefull for most situations. But it looks like that between -12 and 0 the response in camera is not the same as in other meters. Like if it would have some kind of limitor.

 

 

Pat

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I am reporting back to show some photos of my experiences dealing with the gain staging of the black magic. I know that some of you have said that this issue isn't something I should pay much concern to, however, I am a stickler for detail oriented learning, and I would very much like to get to the bottom of why I am experiencing these problems.

The BMPC does not seem to receive my dBs of calibration tone at a 1:1 ratio. 1dB of gain in the Black Magic world seems to have a different numerical value than dBs in the rest of the world.

 

 

 

- I send -12dB tone to camera.

- I then line it up to the -12 marker on the cam's meters by adjusting the cam's preamp.  

 

post-10463-0-85025600-1427857993_thumb.j

 

 

 

 

Perfect. No problems yet.

 

post-10463-0-13334600-1427858004_thumb.j

 

 

 

 

 

- As an experiment, I turn my output tone in the Nomad down to -18dB. 

- Looking back at the cam's meters, they do not match up to the -18dB marker. My signal is too hot by about 2dB.

 

post-10463-0-07973100-1427858014_thumb.j

 

 

 

 

- I continue the same experiment by turning my output tone in the Nomad further down to -24dB. Same problem. My signal is too hot by about 4dB. 

 

post-10463-0-20780100-1427858024_thumb.j

 

 

 

 

- And then I turn my output tone in the Nomad all the way up to 0dB to see if it will match 0dB on camera meters. Same problem, but this time signal is too cold by about 7dB.
 

post-10463-0-46095400-1427858035_thumb.j

 

 

 

 

- And finally, I decide to turn my output tone in the Nomad back down to its original calibration position of -12dB to prove that it will go back to a matching metric. And what do you know, it perfectly matches on the meter of the camera once again at -12dB. 

 

post-10463-0-13334600-1427858004_thumb.j

 

 

 

 

Am I doing something incredibly obviously wrong here? Thanks for reading. 

 

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I am reporting back to show some photos of my experiences dealing with the gain staging of the black magic. I know that some of you have said that this issue isn't something I should pay much concern to, however, I am a stickler for detail oriented learning, and I would very much like to get to the bottom of why I am experiencing these problems.

The BMPC does not seem to receive my dBs of calibration tone at a 1:1 ratio. 1dB of gain in the Black Magic world seems to have a different numerical value than dBs in the rest of the world.

 

- I send -12dB tone to camera.

- I then line it up to the -12 marker on the cam's meters. Perfect. No problems yet. 

- As an experiment, I change my output tone to -18dB. 

- Looking back at the cam's meters, they do not match up to the -18dB marker. 

- I try the same experiment with -24dB. Same problem. 

- I try the same experiment with 0dB. Same problem. 

 

Am I doing something incredibly obviously wrong here? Thanks for reading. 

attachicon.gif1.jpg

attachicon.gif2.jpg

attachicon.gif3.jpg

attachicon.gif4.jpg

attachicon.gif5.jpg

 

First, I would start by switching the camera's audio input type from mic to line. The outputs coming out of your Nomad or Maxx are line level outputs, and as such are a hotter signal than the mic level inputs on the camera. So start by matching the impedance as best as possible between your outputs and inputs.

 

Then, depending on how you have your Tone routed in the Nomad / Maxx, check to see what the compressions settings are on your output bus (and on card tracks if you are routing card tracks to output buses), for this could a reason for the reduced dynamic range going into the inputs.

 

Lastly, since the BMPCC has a single 3.5mm stereo jack, I wouldn't recommend expecting to be able to get usable (printable) audio out of it. The fact of the matter is that this camera is a budget camera, and as such, I wouldn't expect BlackMagic to have invested a lot of money or effort into putting high quality components for its audio inputs. I would consider it reference / scratch track at best.

 

Hope that helps.

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First, I would start by switching the camera's audio input type from mic to line. The outputs coming out of your Nomad or Maxx are line level outputs, and as such are a hotter signal than the mic level inputs on the camera. So start by matching the impedance as best as possible between your outputs and inputs.

 

Then, depending on how you have your Tone routed in the Nomad / Maxx, check to see what the compressions settings are on your output bus (and on card tracks if you are routing card tracks to output buses), for this could a reason for the reduced dynamic range going into the inputs.

 

Lastly, since the BMPCC has a single 3.5mm stereo jack, I wouldn't recommend expecting to be able to get usable (printable) audio out of it. The fact of the matter is that this camera is a budget camera, and as such, I wouldn't expect BlackMagic to have invested a lot of money or effort into putting high quality components for its audio inputs. I would consider it reference / scratch track at best.

 

Hope that helps.

 

 

Thanks for your thoughts.

 

I knew someone was going to mention MIC/LINE level. I am using a Sennheiser G3 system to send audio to camera.  I have never had success on any camera using LINE input settings with this hop. Even my computer audio interface at home requires that I set it to MIC in order to get any signal at all. This is the same for every camera I have used it with including the Red Epic, Sony fs55, Red Dragon, and Canon C300. Any thoughts about why it wont seem to output to LINE level? I generally set the tx to about -27 and I set the rx to +12. But, maybe I should be asking this question about the G3 on a different thread.

 

To address your comment about the output compressors possibly being the problem, I highly doubt it. I use some light compression on the outputs and the cards, but nowhere near enough to have such an effect. Besides, it wouldn't explain why I never have the same problem calibrating to any other device (cams mentioned above & my computer's audio interface). The value of a decibel stays as a 1:1 dB ratio (matched accordingly to changes made on Nomad's output tone level) on all other devices I have ever connected to.   

 

Also, I'm using a locking connector to 3.5mm for the G3, in order to get audio into the cam. I know that this isn't the highest quality method of connecting audio to camera, but I'm afraid our editor is a little demanding about requesting a quality track printed to video (probably too lazy to sync in pluraleyes).

I'm out of ideas. Anyone else have any?  

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Oh absolutely. Your using a Sennheiser G3 in your signal chain between the output of your recorder and the input of the camera. I'm pretty sure that's your issue. It all has to do with gain staging and impedance matching. My original comment was under the assumption that you were hard lined to the camera, since you never made mention of any wireless in the signal chain between your recorder and the camera.

The input on your G3 transmitter is a mic level input, whereas the outputs on your recorder are line level. By connecting a line level output to a mic level input, you are essentially reducing the dynamic range of your audio program. On top of that, the G3s are notorious for further reducing SNR and dynamic range due to compander noise and to the output not producing a true line level signal as it should.

So your metering will never match. Only using an actual camera hop / link between recorder and camera will give you matched metering. The transmitter will be able to take in line level, and the receiver will be able to output line level.

Using a G3 between recorder and camera should be strictly for guide / reference / scratch track only, which seems like what you are doing anyway since the editor is using plural eyes to sync. Plural Eyes need not both the video audio and the audio file to have the exact dynamic range, they just need the exact or almost exact program content, as it does syncing via waveform matching.

Hope that helps.

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So your metering will never match. Only using an actual camera hop / link between recorder and camera will give you matched metering. The transmitter will be able to take in line level, and the receiver will be able to output line level.

 

Thanks for your responses, but I am afraid I am going to have to disagree with you. I have tested this G3 setup with other cameras and with my computer's audio interface, and the metering when calibrated, keeps a 1:1 ratio on all meters. When the output tone in the nomad is turned up or down, the other devices always match perfectly.  The BMPC is the only device which behaves with this unique problem. 

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Thanks for your responses, but I am afraid I am going to have to disagree with you. I have tested this G3 setup with other cameras and with my computer's audio interface, and the metering when calibrated, keeps a 1:1 ratio on all meters. When the output tone in the nomad is turned up or down, the other devices always match perfectly. The BMPC is the only device which behaves with this unique problem.

That's not really how that works, but no problem.

I would say to truly test the difference, try plugging in directly from your recorder to the camera and see if it yields other results. Outside of the reduction of dynamic range that the G3 produces, it may just be an issue with the camera itself.

Anyway, good luck!

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I am going back to set tomorrow and I will test with hardwired connection and report back. 

 

My brother owns a BMPCC, so I was able to test it out myself. Conclusion: it's definitely the camera.

 

I went straight from both my Nomad and my Maxx into the audio input of the BMPCC. I set the tone to 0dBFS, set-up the camera to line level input, and adjusted both the output level on my Nomad and the input levels on the camera until it matched 0dBFS. I then went ahead and reduced the level of tone on my recorders to each of the first couple of markings in the camera (-6dB, -12dB, -18dB, -24dB). The first -6dB seems to match (highly doubt it's exact though), the rest are most definitely off.

 

See the pics below:

post-8621-0-06608700-1427904907_thumb.jp

post-8621-0-28432500-1427904947_thumb.jp

post-8621-0-71883400-1427904952_thumb.jp

post-8621-0-44734900-1427905007_thumb.jp

post-8621-0-28477100-1427905010_thumb.jp

 

For the sake of testing, I also tried switching the input on the camera to mic level, after having to readjust the outputs levels and input levels to avoid clipping and get back to 0dB, I obtained the exact same results that I did above.

 

As I stated in my initial reply post, I wouldn't trust this camera to have appropriate high quality audio components, capable of accepting +4dBu line level inputs or the appropriate dynamic range to match the outputs of your recorder. For plural eyes, what you've been doing is more than fine. I wouldn't stress it.

 

Cheers,

José

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As I stated in my initial reply post, I wouldn't trust this camera to have appropriate high quality audio components, capable of accepting +4dBu line level inputs or the appropriate dynamic range to match the outputs of your recorder. For plural eyes, what you've been doing is more than fine. I wouldn't stress it.

 

Cheers,

José

 

 

Hey dude, 

 

Thanks for taking the time to get your gear out and replicate the problem. At least now I know I am not crazy (or incompetent  8) )

I am going to get back to Black Magic and link them to this forum as they claimed they have never heard of this issue before. I am also going to inform my editing dept. that they will have to treat the scratch track for what it's worth. 

I guess someone forgot to carry the 2 when coding the meters on this camera. 

 

Thanks for the help confirming this issue again. 

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  • 2 weeks later...

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