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Guest post: Nikon D4 and D800 audio levels

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While we are entering the slow summer months (Nikon seldom announces major products during that time), I have prepared several guest posts to keep us entertained. Today's article by Otto Peter is on the audio levels of the Nikon D4 and D800 DSLR cameras (check also Otto's previous guest post on how to modify the Yongnuo RF603N wireless remote flash trigger to fit non-Nikon flash trigger sources). If you have an interesting idea for a guest postyou can contact me here.

Nikon says nothing about audio parameters of the D800, so I measured some of them. I have my own D800, and I was permitted to record some test signals with a D4 at a local dealer. I did not care about the built in microphone, and used only the external audio input. I also did not concern myself with auto sensitivity. Signals were generated by an Audio Precision System One audio analyzer, recorded on a memory card, extracted from the video stream on a PC, and the digital audio data was either fed back into the System One, or viewed in time and frequency domain in Adobe Audition. While I took reasonable care to provide correct results, I am known to have erred at times – so I beg pardon, should I have got something wrong.

Worst news first – frequency response

There is no bass. The frequency response of the D4 is identical. The lower limit of the D800’s audio band is too high for proper reproduction of most male voices, let alone environmental sounds. This might make sense for the built in microphone, as it somewhat attenuates noise from holding and operating the camera, but even then, I would expect the roll-off to start at a lower frequency. Two cascaded first order high-pass filters, each with a cut-off frequency of 77Hz, fit this curve quite well. I was able to extend the lower 3dB band limit from the camera’s native 120Hz to 30Hz by applying the parametric equalizer of Adobe Audition 3.0.1 twice, bass shelve set to 27Hz, +10.7dB, first order (second order applied once would not work). I did not fiddle with the values too much, but the result is within 1dB of what I tried to achieve.

Input sensitivity and level meters

The maximum amplitude before clipping is 2.83Vpp (peak-to-peak) at sensitivity setting 1, which corresponds to a sine wave of 1VRMS (root-mean-square). This is true for all frequencies – the bass attenuation is done later in the signal chain, and the input amplifier cannot take higher amplitudes. At sensitivity 20, the maximum amplitude before clipping is 1.27mVpp, or 450µVRMS sine. Between sensitivity 1 and 7, the steps are 4.48dB on average, and between 7 and 18 they are 3.08dB. The last two steps are probably meant to be close to 3.08dB as well, but input amplifier noise results in clipping at slightly smaller sine amplitudes and consequently slightly larger steps than expected. Sensitivity settings 6 and 7 are somewhat exotic, as both clearly show signs of AGC (automatic gain control). I did not observe this at the other settings, but I did not spend too much time for that.
Level meters are quite precise, the first yellow bar is 12dB below the red bar, and when the red bar lights up, clipping just begins. Unfortunately, the meters are positioned after the high-pass filter (they are probably derived from the already digitized signal), so they will often not indicate clipping at low frequencies, especially at low sensitivity settings, when the input amplifier clips, but not the converter.

Noise

That’s another problem. Higher sensitivity settings are not useful due to excessive noise. My camera has an SNR (signal-to-noise-ratio) of 90dB at setting 1, but only 28.5dB at 20. That’s about 18µVRMS over the entire signal band (DC to 24kHz). A state-of-the-art audio pre-amplifier chip has something like 0.2µV, which would mean much more useful 67dB SNR. Interestingly, there is less noise at the same sensitivity if the internal microphone is used in a quiet room. While the D4 is better (38dB SNR at 20), it is still far from good.

Distortion

Input signal at 1kHz: 0.7dB below maximum.
Amplitudes of some harmonics relative to signal:
 2kHz 84.8dB
 3kHz 92.0dB
 4kHz 108.1dB
 5kHz 95.4dB
 6kHz 116.5dB
 7kHz 101.2dB
 8kHz 114.0dB
 9kHz 98.6dB
 10kHz 118.6dB
This results in a THD (without noise) of about 0.007%, which is neither fancy nor bad.

Anti-Aliasing Filter

This is much more important for audio than for video. Frequencies above half the sampling frequency, i.e. above 24kHz, should be completely eliminated, frequencies below that limit should be passed on without attenuation. This is not the case in the D800. The first time attenuation reaches 60dB is at about 26.5kHz, which aliases to 21.5kHz in the sampled signal. Up to 48kHz, attenuation varies between 60dB and 75dB. I did not test further. Not exactly impressive.

Input Impedance

2.2kOhm at 1kHz – this is ok for microphone inputs.

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  • Dean Allman

    This is good to know, and it just emphasizes the need to use the audio recorded by the camera as a reference track while editing. Serious audio should be recorded with decent mike(s) and a recorder.

    • Can’t Believe It

      If you’re going to record on a separate device, why not just rent or buy a dedicated video cam? The whole thing is very mysterious, why would the camera companies go to all the trouble of adding video capabilities and then cripple the whole thing with a mediocre audio section.

      • Dean Allman

        Several reasons. Some of it all depends on what you are recording. Audio from a concert is best captured from the stream coming out of the system board the sound guy at the concert is running. The camera audio is used in post as a reference track to sync the music with the vid, then it gets muted out. Cameras can also make a lot of noise during a shoot, or there can be ambient noise that the onboard mike picks up that a directional or lavalier mike will not. Videographers and filmmakers know that great audio is at least as important as great video, and it pays to have great quality equipment thoughtfully deployed.

      • outkasted

        cause it makes money. third party after market is a money maker

      • Nikon Shooter

        They are not “crippling” anything. A lot of times a decent audio rig is larger than a DSLR, so it physically can’t fit inside the camera. If you are serious about your video you use off camera sound. Period. Just like if you are serious about your photography you shoot RAW.

        • Otto

          Yes, they did cripple the cameras. Good frequency response, proper anti aliasing, and lower noise are not a question of physical volume. I cannot speculate about what Nikon thought when they did what they did, but it could easily have been done better. I don’t say that in-camera sound is likely to beat external equipment, though. (just for information: I am an electronics developer)

      • vFunct

        dSLR cameras have better optics than video cameras.

        I record audio separately anyways. Final Cut has automatic audio syncing, and non-Final Cut users should invest in a clapboard anyways.

        • Spy Black

          PluralEyes can sync all audio and video files in programs like Avid or Premiere.

  • kaj

    The recording quality of the internal mic is awesome. It indeed has bad snr. But the the recordings out of the d800 sound quite natural. Record some classical music with it when you have it around and can do it. Will like it.

    Also, distortion sometimes is a wanted thing in records.

    • Gareth O’Neill

      It looks as though the reviewer knew what they were talking about, which is good, because I certainly didn’t.

    • Paulo Feitosa

      If you want distortion, buy a guitar amp, or add it latter: most of us need a clear sound. Classical music doesn’t have much bass – unless you’re listening to a good organ recording – but it does have a lot of soft nuances, where a low signal to noise ratio will sure show.

      • Jo

        Paulo – I have to disagree that “classical music doesn’t have much bass” outside of an organ. As a recording engineer, that’s simply not true at all, unless you are recording a solo flute or clarinet or something. A symphony orchestra or even just a piano or cello etc. etc. will absolutely have plenty of bass.

        RE: the test – at the end of the day, if you are really doing high-end work, you almost certainly have external mics AND recorders/pre-amps. I’ve done several music recording projects of classical / jazz music with the D800 so far and it’s awesome. I always am recording with a stereo pair or more into separate equipment.

  • Paulo Feitosa

    Great test. Thank you!

  • Dominique

    For a valid test, I’d like to see the data of the source signal (or if you prefer, the input signal to the D800).

    • Otto

      Nothing surprising there – just a ruler straight frequency response,
      measured at the cable going into the camera. I used a multitone signal
      for the graph, which gave the cleanest result: 31 frequencies in third
      octave steps summed together, power spectrum estimation at those
      frequencies, graph interpolated between them, calculations done by
      proprietary algorithms in the System One analyzer. Of course I checked
      the source signal when I saw the D800′s dreaful frequency response. I
      also verified it with a stepped, purely analog sine sweep (THD below
      0.0005%). Distortion, noise, and anti aliasing properties were measured
      using that same analog sine generator, and/or by looking at the digital
      result in Adobe Audition 3, using Frequency Analysis, and Amplitude
      Statistics.

  • Aldo

    I don’t know about you guys… but I find the built in mic on the d800 outstanding for what it is. I have recorded live bands with it… and regulating the audio levels manually, I got amazing results.

    • Spy Black

      You’re recording live music with a mono mic on the camera?

      • Aldo

        You asking if I’m recording with the mic in the camera?

        • Spy Black

          Yes, you’re recording live music with a the mono mic in the camera?

          • Aldo

            The mono mic in the camera?

            • Spy Black

              Yes, the D800 has a single monophonic microphone.

            • Aldo

              are you talking about the microphone inside the camera, the one that comes integrated?

            • Spy Black

              OK, got it.

  • TheBusyGuy

    Otto,

    Despite the drawbacks, some of us would still like to be able to record interviews and field sound directly into the camera either because we are a one-person crew or because of time limitations.

    So what should we look for in a lavalier or shotgun that would work around the shortcomings in the audio chain. Is there a certain response curve that works better? Or have you found any particular microphone to sound better specifically with your D800?

    • Dean Allman

      Watch what RODE is up to: http://www.rodemic.com/ They are the best that I have found so far addressing issues in the DSLR vid market.

    • Otto

      Use a preamp to get an input level high enough for sensitivity close to setting 1, and boost low frequencies in post. Don’t turn on any low frequency attenuation of the microphone. Interviews will be perfectly ok, I am sure, and you’ll probably be able to use the result in many other cases.

      Cannot recommend any microphones, though.

    • Nicolas

      I am a “one man crew”, I shoot documentary, interviews, ambient sound…

      I use a rode videomic pro plugged into the D800 when my subject is close, and I plug it into a Zoom H1 when I’m more than 2 meters away from the person i’m recording.

      I’m NOT a sound engineer, I don’t know if the amp in the D800 is better or worse than the zoom. My empirical testing showed me the zoom might be a bit better, but plugging the mic straight into the camera allows me to monitor my sound as I shoot (something i can’t do if I leave the mic and Zoom on a stand) and saves me some hassle in post, so it is my prefered workflow, even though I might sacrifice some quality.

      Again, I’m not a trained sound engineer, I tried the D800′s mic, an audio technica mic, my zoom H1′s mic and this rode, and the rode gives me the results I like the most.

      Whenever the budget allows to hire a sound engineer, i do. Because they’ll record a better sound, but mostly because that’s one less thing to think about, and i can focus on my images ;)

  • Spy Black

    Sorry in advance for this long-wing response, but this made me curious about my own gear. I’m not familiar with your testing hardware, but I’ll assume you fed in an analog signal from your testing rig into the “mic” input on the cameras. I did a quick and dirty test on my own D600 and D5100 cameras to see what I’d get. The D600 didn’t seem to have the rolloff you got, and the D5100 actually had a bass BOOST that surprised me.

    I don’t have such test gear, but I simply generated a 16-bit/48k white noise signal in Cool Edit Pro (Audition’s predecessor), took the headphone output from a Behringer BCA2000 A/D-D/A interface and fed the white noise into the cameras. As a reference for the D/A output coming from the BCA2000, I also fed the signal into a Tascam DR-07 recorder. I know this isn’t the most scientific approach (the A/D in the DR-07 could have induced it’s own variation, although basically it did not), but it gave me a pretty decent view of things.

    I set the headphone output until I had a -12dB reading on the D600 meters. I didn’t change the output for the other units, and could only get -18dB on the DR-07, and less than that on the D5100 with it’s sensitivity input set to HIGH (there’s no level settings or meters on the D5100). I took the .mov files generated by the cameras into QuickTime Pro and exported the audio as .wav, and imported them into Cool Edit.

    So here are linear and log analysis views from Cool Edit. I scaled the analysis box so I could fit them all into a 1024×768 window (the most res I can have with my Photobucket account, click on the magnifier to go to 1:1 view):
    http://tinyurl.com/q5932xj
    http://tinyurl.com/oa38wul

    The D600 and DR-07 both sound fine (and the plots back the sound up), but the D5100 sounded like it’s treble was truncated even though it mostly isn’t, save for a small dip at ~8k. The low-end boost however is the main culprit there.

    Again, I know this isn’t exactly scientific, but it essentially confirmed what I heard. So I’m wondering why you got what you did from those cameras. Did they SOUND like they were missing bass? I have to assume that the D5100′s setting was adjusted and optimized for the internal mic and just applied the same treatment to the input jack, which is stupid (I didn’t make an internal mic test with the D5100 to confirm my suspicions). The D600 appears to have a neutral input at the jack, so I’m surprised the D800 and D4 would apply some type of attenuation to their input jacks.

    Of course, ultimately if you want the best audio you’ll need to use a quality audio recorder, and sync up with PluralEyes, or record a timecode sync signal into the camera if you have such gear. However it seems to me I can get decent enough audio feeding directly into my D600 at least.

    • Otto

      White noise is fine, but averaging over many results would significantly clean up the graph. I did not succeed in finding any programs helping with this, but maybe you are more skilled at searching the internet. CoolEdit can export the spectrum to the clipboard as text, but you’d still have to convert it back to linear amplitudes, and do that for many spectra before converting the sums back to dB.
      Use an FFT size as large as possible (and a clip that is at least as long), as this gives you the best frequency resolution. The lowest frequency you can observe just fits into the window (e.g. 0.732Hz = 48kHz / 65536 – you had 48kHz / 2048 = 23.44Hz), the second frquency is at twice the first, and so on. Blackman-Harris is ok. Use log view to interpret the result, as you cannot see what’s going on at low frequencies in linear view. The graphs from the D5100 proove it: in log view, it becomes obvious that there is not a bass boost, but serious 12db (or so) attenuation above 4kHz, which correlates with what you heared.

  • zoetmb

    Sorry, I disagree about the low frequency response (on my D800). That might be true with the built-in microphone (which is amazingly good considering its size – my biggest complaint is that it picks up camera noise), but I bought the Stereo Videomic Pro from Rode and I was absolutely amazed at the low frequency response. I recorded a short bit at a rock concert recently and the bass guitar comes through fantastically when played back on any sound system that includes a subwoofer. I was very impressed. (And for the record, I’m an ex-recording engineer.)

    The only problem with the Rode mic mounted on the camera is that the stereo image changes when you move the camera. So if I’m on a live violinist (no sound system) and I pan left to catch another musician or someone’s reaction, the sound of the violin moves to the right. Etc.

    Obviously, as others have posted, a separate sound system would be better. Multiple mics would be better. If you’re shooting people, hidden radio mics would be better. But when I’m going to shoot by myself or shooting family videos, I can’t work with ancillary equipment and the D800 with the Rode does extraordinarily well. It’s not the way you would shoot a pro movie. But it’s great for what it is.

    • Otto

      I did not measure the performance of a microphone-camera system, but only that of the camera alone. Mic jack in -> file out. I did try a borrowed Nikon ME-1, and compared the electrical signal at it’s output with the recorded data – same LF rolloff as with purely electrical test signals.

      • Otto

        I should add that this was, of course, a purely electrical test, too, as the acoustic properties of the mic did not matter. The pupose of that test was to make sure that there are no dirty tricks involved, like turning off the high pass filter when a genuine Nikon microphone is connected – which is not the case.

  • PhoneyConclusion

    So for non-Audiophiles, what is the “bottom line”??? I didn’t see a conclusion paragraph with recommendations. Bottom line it — should we use it, or what do you recommend to replace it?

    • Otto

      Check my response to TheBusyGuy: external mic + preamp to be able to use sensitivity setting 1, compensate bass rolloff after recording in a sound editor (not with an analog equalizer between preamp and camera – this will lead to clipping that the D800′s meters don’t show). That will be ok in many situations.

  • allenfacemire

    Recording audio with DSLR’s is only problematic if you panic. Worst thing you can do is panic.

    I shoot a TV show using XDCAM’s. Love the look. I do lots of pick ups using my D800. I’ve matched it to be pretty damn close to my F800.

    Audio?? Use the camera mic as a reference and record off board. If you are doing serious video work where audio is driving the story…you MUST record off board.

    Double system is not a mystery anymore. I good digital recorder like a Zoom or my favorite, the Roland, is just fine. They cost a few hundred bucks and you can plug grown up mics into it. When you start rolling audio and video, do a hand clap and don’t stop recording until you are done. Pluraleyes and the like, will easily sync the material.

    I love my Nikon D800 but a $3k camera can’t handle the band width it takes to do movie quality sound. It’s damn amazing they can get wonderful video at 25mbs in what is essentially a still camera, and for that I’m grateful. But I’m not going to depend on a still camera to record anything more than ambient reference audio.

    And neither should anybody reading this.

    Anybody has questions about my work flow…feel free to email me at 1stcamera@bellsouth.net.

    Allen Facemire
    Atlanta

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