Tutorial: Getting good in-camera audio on Canon DSLRs

Tutorial: Getting good in-camera audio on Canon DSLRs

Getting great images on a DSLR is easy, but capturing good audio in-camera is a whole different story. Here's a few tips to help you get better audio.

The past: Automatic Gain Control

In the first generation of Canon HDSLRs there was no way of controlling the levels of the in-camera audio (Canon 5D Mark II, Canon 7D, Canon 550D). Instead, audio levels were controlled by the built-in Automatic Gain Control (AGC). What this feature did, was raise the volume in the silent parts (leading to huge amounts of hiss and amplification of any background noise) and lower the volume in the louder parts. While being a very handy feature for the casual shooter (no need to worry about setting the correct levels, or changing the levels depending on the situation), it was very hard to get usable audio in an interview situation, forcing serious HDSLR users to record the audio seperately on devices like the Zoom H4n, and synching the audio in post.

Much has changed since those early days of HDSLR video: later models like the T3i, T4i and 5D Mark III were equipped with manual audio control, and Magic Lantern brought manual audio control to the 550D/T3i and 5D Mark II. Canon recently even released a firmware update for the 7D, allowing you to manually set the audio levels on that model. So, now every Canon HDSLR has (or can have) manual audio control, we can finally record audio directly in camera, right?

Well, there’s another issue… The quality of the internal audio circuit on Canon DSLRs just isn’t all that good. When you set the manual audio levels somewhere halfway, you can clearly hear a lot of noise/hiss, and it’s a kind of hiss that is hard to remove in post-production. Luckily there’s a way to get past this limitation, and record usable audio in-camera.

Step 1: get a microphone with a built-in preamp

To get good audio we need to feed the camera a loud signal from a microphone that has good internal preamps. Examples of such microphones are the Røde Videomic Pro (which is small and has a built-in +20dB switch) or the Sennheiser Wireless Mics (which have a built-in adjustable preamp). For Microphones that don’t have a built-in preamp like the Røde NTG-2 and many other mics you could use an external preamp like the JuicedLink DT454.

The Sennheiser wireless receiver has a built in preamp

Step 2: lowering the in-camera volume

Once we’re feeding the camera a clean and loud signal, we can lower the internal preamps of the camera (reducing the hiss that is caused by these preamps). Usually I set it to just one notch from zero.

Setting the audio level to just 1 notch from zero

What we’ve actually done is moving the task of amplifying the signal to the external preamp, so the noisy internal preamps of the camera don’t have to work so hard. This lead to a much cleaner signal, because we’ve replaced the noisy preamps with the clean preamps of the microphone.

Is it usable?

I’ve used this method for many interviews, some of which got broadcasted on national television, and the audio quality is very good, especially with the Sennheiser Mics. It keeps my rig small, reduces the risk of things going wrong (like forgetting to press the record button on the H4n) and saves me a lot of time in post-production. Try for yourself, and let me know what you think in the comments below.


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