Why DSLR Audio Recording Sucks and What To Do About It
There is no question that video recording with a DSLR such as a Canon EOS 7D or 5D Mk II can create absolutely stunning visual effects. The fact that we are seeing cameras like this used to shoot feature films, TV series, commercials, and reality shows proves that they truly are broadcast quality devices. However…if you have tried to shoot any video with these cameras, one of the first things you will notice is the horrible audio quality they have. In this article we are going to dive into why this problem exists and some solutions to help solve the problem so that you can create excellent videos complete with excellent sound.
Isn’t “Suck” a little harsh?
Actually, to say that the audio recording sucks is an understatement. My two-year old $600 Vixia palm sized camcorder does better audio than my 7D. So no, the poor audio recording is a major failure on the camera manufacturers part and can actually be fixed via firmware if they chose to. One thing that may surprise many people is that they get better sound from the on-board microphone than they get with a high-end studio microphone. No way, the cheap, tiny, built-in mic works better…how is that possible? The answer is the one thing that makes the on-board mic work “so so” and higher end microphones almost unusable is Automatic Gain Control (AGC). What AGC does is to monitor the audio stream and then boosts the audio signal to make sure it is picking up the audio. The reason this sort-of works on the built-in microphone is because of the ambient noise in most situations. With any ambient noise, the AGC will “hear” some noise and the AGC won’t kick in. With a really good microphone, you can get such a clean audio signal that there is no ambient sound which will send the AGC into overdrive, thus filling the audio stream with tons of noise as it tries to boost the signal.
All the camera manufacturers have to do is to allow the ability to disable AGC in the firmware or preferably have a setting option such as High, Medium, Low, Off. This would allow for selectable gain control depending on the situation and the microphone used. That’s it, a simple firmware change and there would be no need for this post. However…none of the DSLR manufacturers have seen fit to include this obvious setting.
Creating Non-Sucky Audio
There are several ways to get really clean audio and we will look at some of these options so you can decide if one of them is more suited for how you want to work.
Secondary Recording Device
From the dawn of time (or at least since video recording started) high-end video production has consisted of using separate devices for video and audio recording. Have you ever seen a clap board and wondered what it was for? A clap board is used by the editor to sync the audio and video since they are recorded on different devices. For cinema production, this is a tried and true process so moving to DSLRs does not affect their workflow at all. For budget filmmakers who have used camcorders, moving to separate audio and video tracks can be frustrating and difficult to sync up properly. Add to this that even a slight variance between the two devices and a long film clip can actually drift out of sync. One of the most common secondary audio devices is the Zoom H4N. I actually have the older Zoom H4 which isn’t available anymore.
Pros: Excellent Audio
Cons: More work in post, additional expense
AGC Disabling Mixer
For post production speed it is definitely better to have the audio and video already mixed together. This prevents and audio drifting and issues with syncing (until you start using multiple cameras anyway). One solution I have found is the JuicedLink DS214 Amp which features AGC disabling. The way the AGC disabling works is that the DS214 feeds a generated tone through one of the stereo channels while sending the microphone audio through the other channel. This tone sound essentially shuts down the AGC because it becomes overwhelmed with noise thus lowering the gain to the minimum and letting the camera record very clean audio. With the DS214 costing $144, this isn’t a cheap solution but it does do the trick and as soon as the firmware allows for true disabling of the AGC control, then you can disable this feature.
Pros: Allows variety of microphone gear to work well, less work in post
Cons: Only allows for single channel audio recording, additional expense
Magic Lantern Firmware Hack
While we wait for Canon and Nikon to come to their senses, the folks over at Magic Lantern have created a firmware add-on for some Canon cameras that adds a nice set of features including audio meters and the ability to disable the AGC function. The downside here is that the Magic Lantern firmware is not available for the Canon 7D yet or for Nikon cameras.
Pros: FREE!, True AGC disabling, Auto Meters
Cons: No 7D support, No Nikon support
If you are getting started with DSLR video, it is only a matter of time before you get frustrated with trying to get good, clean audio. Hopefully you will find one of these options to suite your needs and budget to help you get exactly what you are trying to get.