Recording Sound with DSLR Cameras

Chances are you don't have an audio background, so making sure you understand your equipment and taking a little extra time to learn or review some basic rules for capturing good audio is recommended. 

Each DSLR camera is similar but not identical in their audio specifications.

Let's start by taking a look at how to set up the basics to run audio from a camera. All cameras will have similar audio setups, so we will use the Canon 5D Mark II as our example model.

First just look at what the specifications are on your camera. This will help you get acquainted with some of the basic terms and things that can be done with your camera in terms of audio. The following is from the 5D Mark II audio recording specifications:

Sound recording is possible with the camera's built-­in monaural microphone or a commercially available external stereo microphone connected to the camera via its 3.5 mm diameter stereo mini plug jack. With either the built-in microphone or an external mic, the sampling rate is 44.1 KHz and the bit count is 16 bits for both Land R channels. Audio levels and wind filter settings are controlled automatically. Sound recording can be turned off or on in the camera's Live View menu.

Commercially available electret condenser type external microphones are recommended for best results. However, dynamic type or condenser type external microphones that require phantom power cannot be used.

The 5D's built-in microphone is an electret condenser microphone. These microphones used to have the stereotype of low-quality microphones, but now the best models are regularly accepted as professional-grade microphones. The major challenge with audio on DSLR cameras is the audio input and sampling rate.

The Canon 5D Mark II records 16-bit 44.1 kHz linear PCM audio in the camera. With a recent firmware upgrade, you have the ability to control the sound recording as Auto, Manual, and Disabled.

The Auto setting is a form of automatic gain control (AGC). This auto gain control will amplify many ambient noises or sounds, such as wind, car engines, and so on. This amplification of peripheral noise will distract from the dialogue you are trying to get recorded cleanly.

In a movie, it is most important for the dialogue to take auditory precedence because most of the other sound can be added or tweaked in the mix. For filmmaking or narrative pieces, any use of an auto gain audio device will certainly render your project as low budget and not professional. It works great as a reference audio track to be used during post but should not be used for actual audio capture to be used in a final mix. If you are ever in an emergency situation and must use the on-camera audio, turn off the automatic gain control and manually control as much as possible.

Auto, Manual, and Disable audio options

The manual settings are a more recently added function of the camera; they allow the operator to manually control the audio levels. When you select Manual in the sound recording menu, you get a Rec. Level adjustment bar to manually control your audio levels.

As with any audio recording, you want to set your audio levels to "peak" right between -12 db and 0 db. If your audio levels exceed 0 db, then your audio will be clipped, or distorted.

Other DSLR cameras will operate similarly with slightly different menus. For example, the Nikon D3S has a built-in monaural microphone, and a stereo microphone can be attached via the hot-shoe mount. You have the ability to set your microphone settings to High sensitivity, Medium sensitivity, Low sensitivity, Microphone off, and Auto sensitivity through the camera menu.

With any DSLR camera, it is important to read the technical specifications for the type of microphone, input of the camera, and the recording specifications. In general, however, no DSLR camera has audio quality that is good enough to be used as the primary audio recording method for a high-quality project.

Using an External Recording Device

In reality, if you are going to make a movie or other dramatic project, you must use an external recording device and record in a "double system." Recording a "double system" means capturing audio with the camera as well as an external recording device. Think of your project just like a film shoot: record the image in the camera, get your high-quality sound from a separate device, and sync it in post.

Practically speaking, it is best to capture audio externally. It is easier and more effi­cient to get better audio using a dual recording system where the camera records image and audio for matching purposes and a separate audio system is used to record audio. These devices allow for a direct digital recording from a microphone and provide a much higher ­quality recording.

It can seem intimidating to have a separate system for recording audio, but even if you are doing audio yourself, it is actually easier to have a dedicated audio setup that functions separately from your camera. If you keep them separate, you have the option of getting several more channels for audio, the ability to record performers with multiple microphones, greater ease with post-production mixing because of multiple channels, easier voice-over or dubbing capabilities, freedom from having extra microphones or cords being attached to your camera, and the ability to hand over the role of audio to another person (ideally a professional or at worse an ambitious assistant).

Audio for DSLR projects is usually captured externally by using one of a variety of digital audio recorders. These devices have many different features, but the key components that you need to look for are a device that can record high-quality audio with multiple inputs, multiple-channel ability, storage capacity, and ease of use including the ability to label takes.

When capturing audio externally, you may also need to add an audio mixer to the gear list if you have multiple tracks that need to be recorded concurrently or live.

You have a variety of options for external audio recorders. One of the most popular recorders available is the Zoom H4n (right, $299). It can record up to four tracks simultaneously via two onboard microphones and two external inputs via XLR or v.t inputs. It can record in multiple formats, but you will want to record using WAY audio files (somewhere between 44.1 kHz 16-bit to 96 kHz 24-bit). A good target rate to do your recording at is 48 kHz 24-bit.

The Zoom H4n records on standard SDHC cards. You can get cards up to 32GB, which at the target rate of 48 kHz 24-bit would give you about 15V2 hours of recording time.

If you want to go with a more pro-style audio recording setup, a Sound Device 744T 4 track digital audio recorder is a good option. The 744T is a powerful four-track file-based digital audio recorder. It records and plays back audio to and from its internal hard drive, Compact Flash cards, or external FireWire drives. It writes and reads uncompressed PCM audio at 16 or 24 bits with sample rates between 32 kHz and 192 kHz.

If you are not an experienced field audio professional, this system has a low learning curve, and you can set it up and be running in no time. If you add a Sound Device 422 out­ board field mixer, you are a truly portable audio station. The removable, rechargeable bat­tery is a standardSony-compatible Li-ion camcorder cell.

The 744T (left) interconnects with Windows and Mac OS computers for convenient data transfer and backup. Its recording media (hard drive, Compact Flash, and external FireWire drives) are reliable, industry-standard, and easily obtainable storage.

If you have time during the day, you can download your audio for backup, or if your schedule doesn't allow, there is more than enough storage to wait until the end of the day to dump your audio files and back them up.

Capturing Reference Audio

Even if you are recording to an external audio system, it is helpful to use the audio captured with the camera for reference during post. None of the onboard audio will be used in the final project, but reference audio can save time and answer any syncing questions in post. Even if you are just capturing reference audio, it makes sense to try to capture good reference audio, and a little extra work and effort will save you time on the backend.

The first step to getting better in-camera audio is to upgrade the onboard microphone wherever possible. If you are in a quiet, small location or in a location where a large microphone might draw too much attention, then you may be able to get away with the camera's built-in microphone. With that said, you are risking headaches and extra work in post relying on the built-in microphone even for reference. Adding an accessory shotgun mic for getting the best possible reference audio into the camera will be useful for capturing reference audio.

You can buy a variety of hot shoe-mounted shotgun microphones that you can plug directly into your camera and get a decent reference audio track to use in post. This is essentially boosting what you would get with the built-in camera microphone and making sure the signal strength is good and you don't have things like the noise from an IS lens overpower your reference audio track.

Using these sorts of microphones is a way to create a better audio reference track in the camera that you will use to help sync your audio in post. The audio will still be controlled either by the camera's AGe or by the manual control if your particular camera model allows manual audio adjustments.

If you choose to use an onboard microphone for ambient audio recording outdoors, use an additional windscreen. Any wind will ruin the audio, so a cheap windscreen can save you a ton of headaches in post. Both Rycote and Red Head offer windscreens that will cut out any unwanted wind noise. The H4n also has phantom power if you need to power microphones without batteries or another external power supply. It also has a headphone jack for monitoring, which is a clear advantage because you cannot do this with most DSLR cameras.

Deciding how you are going to record audio is just the beginning of the process. After determining your primary audio recording system and reference audio setup, you will need to plan the audio setup for the shoot. Here is where an audio professional will prove most helpful in deciding what additional gear is required and how to set up a coherent system to record quality audio throughout the shoot. However, often moviemakers are responsible for planning audio, and in any event, it is necessary to be able to understand audio gear in order to communicate with the actors and audio technicians. The next step to recording audio on set is planning the microphones, or ears, of the shoot.

Using an XLR Audio Adapter

Two major drawbacks in recording audio on your DSLR camera are the inability to see your audio levels and the fact there is no audio-monitoring jack so you can listen and adjust your audio while you are recording. An XLR audio adapter can fix one or both of these problems. Any XLR adapter will have a headphone jack that allows you to plug in headphones and monitor the audio live. This allows for quick, small adjustments to the audio during the scene to make sure the audio levels are strong and consistent throughout the scene.

We don't normally recommend XLR adapters because external audio recording is superior. However, if you must record audio directly into your camera, an XLR adapter will be very helpful.

Some XLR audio adapters also have audio meters on the front that visually show you the audio signal strength. This is just another way you can quickly look and make sure your audio signal is strong without being too strong to clip the audio signal.

Another reason to use XLR audio adapters is the ability to use an XLR audio cable as opposed to a smaller, mini audio plug. The XLR cable is a professional audio cable designed to carry a much stronger and better audio signal than what is possible to transmit through a standard mini plug. With that said, we don't consider the benefit of the XLR cables to be a valid choice.

There are a few XLR adapters on the market, but the most prominent is the BeachTek DXA-PRO (www.beachtek.com).

These adapters have XLR inputs, phantom power, and gain control. That is great, but you still must come out of the adapter and plug directly into the camera's 3.5 mm input, thus leaving you with the same 16-bit 44.1 kHz audio you started with. Unless there is some special need for your project, it would be better to just use an external device and not have the extra expense and extra piece of equipment attached to the camera.

Wearing Headphones

Always make sure to use headphones to monitor the sound of the microphone before and during the shoot. The pickup pattern is very directional, and monitoring the microphone will ensure that you are getting the sound you want. Not monitoring can mean that when you get back to the edit suite, you discover that the entire day of shooting is worthless because your actors sound like they are speaking to you from a cave .. .in the Antarctic.

Get the full ear cup style. They provide for a great seal for maximum isolation. Cutting down on outside noise really helps you hear what you are getting.

Do not use the in-ear bud style for monitoring or recording audio. One bad feedback squeal, and you can permanently damage your hearing.