Tuesday, June 02, 2009

Capturing Sound For Video

This post is inspired by the Pentax K-7, the first Pentax camera to shoot proper motion video, in HD no less. A lot of still photographers have little experience with video; while I am not a video expert I do know something about sound. So I hope this will be a useful introduction.

This article will outline seven approaches to capturing sound for video, in order of increasing complexity, cost and quality. I will mention some specific products along the way. These are illustrative; other products may do just as well. But these have been recommended by many.

1. Use the built-in microphone

This is the simplest solution as there is no additional cost and everything you need comes with your camera. The sound quality will be abysmal, however. This approach is best only for silent video or where you will add all audio in post-production.

2. Mount an external microphone on camera

This requires that the camera has a microphone input, which the K-7 does. Such a mic mounts directly on the accessory shoe of a video camera, or the hotshoe of a still camera. For $150 the RØDE VideoMic provides many advantages over Method 1. First, the mic is on a shock mount, to reduce handling noise. Second, it has a foam windscreen to prevent wind noise. However it is certainly advised to get a proper "dead cat" wind sock to cover the mic completely. This is true in all cases, but especially when using a directional microphone.

And that is the third advantage: this mic has a super-cardioid pickup pattern, meaning it is more directional. Sounds from directly in front of the mic will be favoured, while those from the sides or rear will be attenuated. Point the mic where you point the camera and pick up the sounds from that direction.

Fourth, this mic will give you massively improved audio quality in terms of lower noise floor, greater ability to record loud sounds, less distortion, smoother frequency response, etc.

Fifth, the mic has a built-in high-pass filter. Engage this to roll off low frequencies and kill rumble before it ever gets recorded.

And finally, this microphone is flexible enough to be used in the Method 3. scenario.

There simply is no reason to use Method 1. when for a reasonable cost you can leapfrog to all the advantages of Method 2.

3. Get the microphone off the camera

In order to get closer to the sound source, or to pick up directional sounds that do not happen to be exactly where the camera is pointing, we must get the microphone off the camera entirely. The RØDE VideoMic can convert to use on a boom pole, a tripod, or a hand-held grip. Each of these have advantages depending on the use scenario. A tripod is fine for studio use; a boom is perfect for targeting dialogue; a hand grip might be best for roving sound gathering or times when you need to be a bit less conspicuous. Of course it can be difficult holding both a mic and a camera, though there are tried and true methods for operating a boom in this way. Check YouTube and elsewhere for video demonstrations.

The RØDE PG1 Pistol Grip ($30) is designed specially for this microphone.

4. Buy a better microphone

If you wish to operate off-camera and want better sound quality, there are several battery-operated microphones you should consider. RØDE's own NTG-2 has improved frequency response and noise characteristics. The Audio Technica AT897 ($260) is in the same range. For the flexibility of modular microphone capsules, the Sennheiser K6 System should be considered. The ME 66 "short gun" and ME 67 "long gun" are both good choices depending on how directional you need to be. The K6 + ME66 combo is around $500.

What is the best way to mount a microphone? Most prefer a "blimp" housing for the best suspension and protection from wind and handling noise. These setups once cost a fortune, but the RØDE Blimp is a more reasonable $300, especially when you consider it includes the suspension, casing, trigger handle, "Dead Wombat" windshield and a cable. Cheaper yet are certain products from India available on eBay, but these are not as complete or as well made.

For a boom consider the RØDE Boompole which is cheaper than many ($150) but still made of aluminum. You don't want your valuable microphone on the end of a plastic stick!

5. Record to a field recorder
Your camera is not a great audio recorder. Dedicated digital recorders have been released by the droves in the last few years. Some have built-in microphones, some are pocket-sized, some have professional features -- the Tascam DR-1, Edirol R-09, Marantz PMD620, Zoom H2... the list goes on.

I should mention here that all of the microphones we are considering are of the condenser type. These require power to operate. There are three main sources of microphone power. The first is from batteries inside the microphone housing itself, the second is a low voltage source known as Plug In Power (PIP) and the third is a higher voltage (48V) source known as phantom power. I will ignore PIP since it is not terribly suited to professional recording (there are exceptions).

In this section I will assume we are still using battery-powered microphones, so our recorder need not have the facility to provide phantom power. This means it can be significantly smaller. Buy something like the Olympus LS-10 which is tiny but of high quality. At this point you will need a dedicated sound person to record your audio. You will also need a way of synchronising the video and sound recordings. A simple time-tested method is to use a clap-board or similar "slate". The visual of the board and the sound of the impact can readily be lined up in a digital video editor. It's old fashioned but it works.

6. Use phantom power
In order to use a (generally) higher class of professional microphone, one needs to supply it with phantom power, either from a recorder or a separate device dedicated to the purpose. The most full-featured and reasonably priced recorder is the Fostex FR-2LE ($650). Unlike the minute Olympus LS-10, which one can use hand-held, the FR-2LE is designed for over-the-shoulder use. With this recorder, one can use RØDE's top-of-the-line shotgun, the NTG-3 ($700) or the industry-standard Sennheiser MKH-416 ($1100).

7. Use time code
Professional sound for video requires time code for accurate synchronisation. That's why recorders like the Sound Devices 702T ($2500) are used in combination with video striped for time code. Since the Pentax K-7 is not in that class of recorder, we can safely forget this option!

Here is a final list of the suggested configurations and their approximate total cost. I omitted the timecode option.

1. $0
2. RØDE VideoMic = $150
3. RØDE VideoMic + RØDE PG1 = $180
4a. AT897 + Blimp + Boompole = $610
4b. K6 + ME66 + Blimp + Boompole = $950
5. K6 + ME66 + Blimp + Boompole + Olympus LS-10 = $1250
6a. RØDE NTG-3 + Blimp + Boompole + Fostex FR-2LE = $1800
6b. Sennheiser MKH-416 + Blimp + Boompole + Fostex FR-2LE = $2200

This may look like a large investment, and it is. But if you want to make professional or semi-pro videos you have no choice but to pay close attention to the sound. It makes no sense to spend one or two grand on the visuals and nothing on the audio. Your finished product will show the lack.

But by no means am I suggesting you need to spend $2200. I have merely outlined possible options. At least consider being somewhere between Methods 3 and 4.

For more information on microphones for video, I refer you to Ken Stone's excellent articles As I Hear It - Choosing the Right Microphone and Low Cost Shotgun Microphone Comparison. There is also a wealth of information out there on the various video forums.

But I do hope this article has at least pointed you in the right direction(s).



robin said...

Ned Bunnell, the President of Pentax USA, has an article with pictures of the K-7 with the RØDE stereo mic mounted.

robin said...

There's also an informative thread on Pentax Forums you should read.

robin said...

For more detail you may wish to read my trilogy or articles:
* Summary of Portable Digital Audio Recorders
* Which Portable Digital Audio Recorder?
* Choosing An Audio Recorder For Ultimate Sound Quality

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