Wednesday, December 1, 2010

HDSLR Audio Round Up

HDSLR Audio Round UpPDFPrintE-mail
Written by Jem Schofield   
Friday, 11 September 2009 16:16
One thing is for sure, if you're shooting with the new crop of HDSLR cameras—Canon 5D Mark II,Canon 7D or the Panasonic Lumix GH1—you’ll need to put some serious thought into your audio workflow. While each of these cameras is capable of producing remarkable images with their large sensors and interchangeable lens systems, they are all pretty awful in the audio department.
Well, each camera does have built in audio capabilities, including a built in mic and a jack to plug in external microphones, but none of them give the user any real manual control over what’s being recorded. There are no meters, no trim knobs and no XLR inputs to use professional shotgun and lavalier microphones. Most importantly, all of the cameras use Automatic Gain Control (AGC) when recording, and it can’t be disabled. This is the real monkey in the wrench.
AGC works on the equality system. If Joe is talking to camera and suddenly an itty-bitty cricket makes a loud sound in the background, the AGC will kick in. It will increase the mic’s gain and try to make the cricket as loud as Joe. As you can imagine, the results can be disastrous. The audio levels will be all over the place, and unwanted noise can be introduced into the recording. It’s the equivalent of an audio roller coaster ride. Not good.
So, in order to combat these inherent HDSLR audio issues there are a number of current solutions that can be used to ensure that you’re getting the best audio on your HDSLR projects.

Double-System Sound
Zoom H4nThe first thing to come to grips with is that if you are going to shoot a real project with an HDSLR, and it’s not MOS, then you’re probably going to have to go old-school and record dual system. I will discuss options where you can record directly to camera a little later, but for the cleanest possible audio for your project, double-system sound is the only game in town. [NOTE: Watch Jem's video on recording sync sound with the Canon 5D here.]
The most popular, cost effective, recording solution being used for HDSLR double-system sound is the Samson Zoom H4n. It’s a portable flash-based recording device that has a built-in stereo microphone and also has two XLR inputs. It’s easy to use, costs less than $350 and the audio it records is very clean. It includes a low-cut filter (also called a high-pass filter, because it lets the high frequencies through but can cut lower undesirable frequencies out), and it can be coupled with the Redhead Windscreen when filming outdoors.
The H4n runs off of two AA batteries or the included AC adapter and is truly the Swiss Army knife of HDSLR recording. It can even be used to record reference audio directly to camera (using its mini jack line out).

Reference Audio & Direct to Camera Recording
When recording dual-system, it’s important that the audio your camera records is as clean and audible as possible. Whether using software to sync your double-system sound (more on that later), or doing it manually using audio waveforms, if you don’t have good levels and clean audio it’s pretty much a game over.
To help you capture better reference audio to any of the HDSLRs mentioned in this round up, there are a few small microphones that can be used. Remember, these mics don’t disable the AGC in the camera, but they will have better pick-up and audio than the built-in mic.
Sennheiser MKE 400 MicThe first is the Sennheiser MKE 400 Compact Shotgun Mic. It’s tiny, mounts to a hotshoe and runs off of a single AAA battery. It has low and high gain settings and also includes a low-cut filter switch. It comes with a foam windscreen, and there is the MZW 400 Hairy Windscreen that can be added for outdoor, windy conditions.
RODE SVMThe second mic is the RODE Stereo VideoMic. It’s considerably larger than the Sennheiser, but it has a true stereo X/Y microphone, a built in shock mount, a high pass filter and a -10dB pad switch when the mic is too hot for the device it is being used to record to. It runs off of a single 9V battery, has great pick-up and even includes a Dead Kitten windscreen for outdoor recording. RODE also makes a mono, very directional, shotgun mic called the RODE VideoMic. It’s another option when you want to record clean audio to your HDSLR.
Sennheiser wireless mic system ENG G2The stealth approach when recording to your HDSLR is to use a wireless mic system like the Sennheiser EW 100 ENG G2 Series. This system includes two transmitters (one for 3.5mm devices and one for XLR devices), one receiver and one lavalier mic. When you want to be on the down low and still look like you’re just shooting stills, this is an excellent option. You can even use the included XLR based transmitter (only one transmitter can be used at a time), when you want to use a boom mic in a wireless configuration.

Under ideal conditions, indoors with next to no ambient noise, you can record pretty clean audio directly to your HDSLR using an external mic. If you want to use other professional mics (like the Sennheiser wireless system mentioned above or a XLR based shotgun microphone), adding a mixer to the configuration can give you even more control.
JuicedLink makes a number of cost effective mixers that have 2 or 4 balanced inputs that output to a standard 3.5mm stereo jack that runs to your HDSLR. Their products include the CX211CX231,CX411CX431 and the CX471. The 11 series doesn’t have Phantom power (the 31 series does), but all versions of their mixers have three gain settings (low-noise preamps), and separate trim knobs for each input. All of the JuicedLink mixers run off a single 9V battery and the CX471 also includes audio level meters.
If you’re not using the CX471, you’ll have to do some test recordings to the camera’s flash card, transfer them to your computer and tweak the levels as needed. As there is no headphone jack on any of the HDSLR cameras, this is something you probably want to do anyway (regardless of the device that you are using to record direct to camera). It would be a best practice workflow each time you record in a new location.
Juiced Link 231 Juiced Link 431 Juiced Link 471

Disabling AGC
The last device I want to mention is unique to the bunch. It’s the BeachTek DXA-5D Dual XLR Adapter. While it was originally designed to work with the Canon 5D Mark II (and has pins that line up with the bottom of the 5DMKII for mounting), it will also work with the Panasonic Lumix GH1 and the Canon 7D.
BeachTek dxa-5dWhat makes this device unique?
Well, the DXA-5D is the only commercial device on the market that was designed not only to allow direct to HDSLRcamera recording, but also to disable the Automatic Gain Control Disable in your HDSLR camera. Pretty cool, huh?
What the device does is send an approximately 20Khz tone to the camera (we can’t really hear that frequency), which tricks the AGC feature in the HDSLR. This allows you to record audio and not worry about giving equal billing to that cricket I mentioned earlier.
The DXA-5D runs off of a single 9V battery and can provide 12V or 48V Phantom power to external mics. It can record in Mono or Stereo and has two ground settings (G1 and G2), which are used to reduce noise. It also has audio meters and a headphone jack to monitor audio.
Under ideal conditions, you can get away with using the DXA-5D to record useable audio. As it disables the AGC in the camera, it can be a great device to use for both direct to camera recording, for certain projects, and to improve the quality of the reference audio that is recorded to the camera. The quality of the audio won’t be as good as recording to a separate audio device like the H4n, but for certain applications it may just do the job. It’s small, inexpensive and probably a good addition to an HDSLR shooter’s kit.

Connecting to the Lumix GH1
While any of the above solutions will work with the Panasonic GH1, when recording audio directly to the GH1 remember that you will need a 3.5mm to 2.5mm adapter. That’s the mic input size on that camera. Other than that, nothing is different.

Syncing In Post
Once you have recorded double-system sound... and you should be, what do you do in post? If you’re using Final Cut Studio for post-production, you’re in luck! Singular Software makes a product calledPluralEyes that was designed for Final Cut Pro and it really works. Once installed, you set up your FCP sequence to match your project’s assets and name it PluralEyes. You then drag your good audio, recorded to an external device such as the Zoom H4n, and the picture and reference audio from the HDSLR camera into the sequence. Fire up PluralEyes, press Sync and it lines it all up in one click – it even creates a new sequence with the synced version. It’s worth every one hundred and forty nine dollars that it costs as it can save you hours of syncing. The company is working on versions for other NLEs, but Final Cut Pro is the only supported application at the time this article was written. [NOTE: Jem's video demonstrates syncing audio with FCP and Plural Eyes. Watch it here.]
If you are using another NLE for post-production, slating each take during acquistion is really important. The current gang of HDSLRs don’t record timecode, so the audio waveforms that are recorded to both camera and your external recording device are your best friends. Slating will give you a definite visual and auditory reference to make syncing in post much, much easier.

When recording audio on a job, each location and job will require that you make tweaks to each of your device’s settings. It’s the nature of the beast.
I find that when recording directly to the H4n, using the Sennheiser ME66/KP6 shotgun mic, that I set the H4n’s recording level to between 55 and 65. This, of course, has to do with the location, type of mic and the placement of the mic. You can also use the H4n’s Phantom Power, but be warned that while it will give you 48V of Phantom power for potentially better dynamic range, it will also eat the AA batteries for breakfast. You’re better off using the adapter if you want to use the device’s Phantom power.
The only real disadvantage I have run into with the H4n is that you can only set one recording level for both of the XLR mic inputs, which are recorded as stereo to two discreet channels. If you’re really serious about your audio (and you should be), you may want to consider adding a mixer such as the Sound Devices 302. This will allow you to control the individual levels for up to three mics and then run those as two outputs into the H4n.
When using the JuicedLink mixer I found that using the medium gain setting produced the best results. This is based on one set up, and while I can’t see using low for any practical applications (I was very close to the mic during the test), I could see using the high gain setting when the mic was further away.
When using the Beachtek DXA-5D with a single mic setup (Sennheiser shotgun again), it seemed that plugging the mic into the right channel, setting the ground switch to G1, activating the AGC disable feature and recording in stereo gave the best results. This effectively gave me a clean audio track in the right channel, the 20Khz tone sent to the camera in the left channel (which can be disabled in post), and the least amount of noise. Again, this was based on one set up but this seemed to be the right combination. I also left the trim knobs all the way clockwise on the DXA-5D as any counter-clockwise adjustments would attenuate (lower or reduce) the input levels. While the DXA-5D is definitely noisier than recording to the H4n directly, it has its place. In good conditions it can produce very useable audio directly to camera, which can eliminate a step in post – syncing audio from an external device.
In the end, though, it’s still best to record double-system sound. While it’s a little extra work, it’s all worth it in the end.

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