Audio Performance of Canon 5D Mark II Camera
Canon's 5D Mark II will likely go down in history as the camera which forever changed the definition of a still camera, and of a video camera. The full-frame sensor "5DII" demonstrates that one device can successfully be used as both a superb still camera and as a creative motion picture camera. The 5D II is showing up in applications where 16 mm film and traditional 2/3-inch sensor high-definition video cameras are used, such as talking head interviews, exteriors, landscapes, and the like. Like most video cameras, the 5DII was designed as an imaging device first...and an audio device last. Sound Devices receives numerous inquiries about the audio performance of the 5DII, both in use when recording to its on-board audio circuit and also when used "film-style" with a separate audio recorder. We grabbed our 5DII, updated it to the latest 2.0.4 firmware, and performed tests. This note includes both measured and subjective observations.
The camera has a built-in microphone with its electret element below the camera chassis. Three vent holes allow for sound passage to the element. The built-in mic performs similarly to those on typical consumer point-and-shoot cameras and much better than the slate microphones on Sound Devices' field mixers and recorders. Similar to those slate microphones, its placement on the camera body makes it subject to picking up handling noise. Here are a few observations about the built-in microphone:
- While not measured, its polar pattern is best described as omni, though the camera body does provide attenuation from sounds behind the camera. The combination of steep low frequency roll-off and its omni pattern helps reduce its susceptibility to wind noise.
- When IS (image stabilized) lenses are mounted and IS is running, the built-in microphone accurately picks up IS gyro noise. Gyro noise is less apparent on more current model IS lenses.
- In low light shots with slower lenses with auto-focus enabled, auto-focus motor noise is picked up.
- If the camera is locked down, with fixed focus, no IS, and the subject is a few feet from the camera body in a controlled environment, the built-in microphone is serviceable for production.
- Firmware revision 2.0.4 introduced manual level control for the built-in microphone to bypass the aggressive AGC.
- There is a lot of digital gain available to the built-in microphone.
External Mic Input
The 5DII has a 3.5 mm, tip-ring-sleeve jack accepting mic-level signals from external sources. A physical connection to the external mic jack overrides the built-in microphone. The manual level control adjusts gain levels for both the external mic input and the built-in microphone. Sound Devices measured a few key specifications to determine the best way to interface with the camera's TRS 3.5 mm microphone input jack. Here are a few important observations:
- For best signal transfer from an external audio source, set the gain to manual control. Adjust it one click above full-off (from the far left). At that position the input clip level is -16 dBu, noise level (unweighted) is -80 dBFS, dynamic range is 80 dB, and the THD at -12 dBFS is 0.048% (unweighted).
- At mid-gain, ~26 dB from off, input clip level is -42 dBu, noise level (unweighted) is -60 dBFS, dynamic range is 60 dB, and the THD at -12 dBFS is 0.45% (unweighted, noise dominated).
- When gain is maxed out on the camera, noise becomes a serious issue. At full gain, input clip level is -70 dBu, noise level (unweighted) is -38 dBFS, dynamic range is 38 dB, and the THD at -12 dBFS is 6.8% (unweighted, noise dominated).
- The 5DII's on-board audio recorder has no trouble recording SMTPE time code when fed to the External Mic Input.
To sum up our advice for interconnection to the Mic Input on the 5DII, run the gain control on the 5DII in manual mode as low as it can go (one click from off). The camera's meters appear to accurately represent signal level in dBFS, so set output limiters on the field mixer, such as Sound Devices 302 or 552, just below 0 dBFS. Like the built-in mic, the External Mic Input connection appears to have a built-in high-pass filter. Frequency response measured at the Mic In connection is:
- 120 Hz - 20 kHz, referenced to 1 kHz, - 3 dB @ 120 Hz, -0.5 dB @ 20 kHz
In practice, the external input on the 5DII is serviceable, and good results can be obtained if care is taken to feed it a signal approaching full scale. Pro video cameras generally have more dynamic range and more full-bandwidth frequency response. The absence of any return audio or real-time headphone output can make recording to camera a bit risky for highly critical applications. While level meters are available, there is no confidence monitoring if a cable is going bad or if a wireless hop is getting an RF hit or drop-out.
The audio performance of a dedicated external audio recorder, like Sound Devices 7-Series Recorders, will certainly outperform the on-board audio of the camera. For applications requiring full bandwidth audio, low distortion, and maximum dynamic range, dual-system is required with the 5DII. That said, it is still a good idea to take advantage of any camera's on-board audio recording capability. Even when running dual-system sound with a separate audio recorder, there are advantages to having audio recorded in two places. If the external recording is compromised or somehow not available, having an on-camera track is better than no track at all. Additionally, with the on-camera audio locked to picture, syncing can be easier in editing, especially if a slate is made out of frame or when using syncing software, such as PluralEyes. The 5DII's original firmware release recorded audio at a sampling rate of 44.1 kHz and recorded picture at a straight 30 frames per second. The new 2.0.4 firmware made significant changes to audio sampling rates and video frame rates. Camera audio sampling rate is now at a more video-friendly 48 kHz and picture frame rates are selectable between 23.98 (shown in the menu as 24 frame), 29.97 (shown as 30, beware!), and 25 frames (when set to PAL). These changes to frame rate make a difference in a time code workflow. These new frame rates now have the camera behaving just like an NTSC/PAL switchable hi-def video cameras without time code. Syncing sound and picture at these new frame rates is straight forward. Editing systems won't introduce any pull-up/down, so wild-syncing sound and picture elements is identical to syncing with traditional non-time code video cameras. In our tests, the 5DII was stable enough to hold lip sync against a 7-Series recorder for 10+ minutes. As mentioned above, using the camera's on-board audio to record SMTPE is another way to sync for dual-system sound.
The introduction of DSLR's into production was initially looked at as the rare exception for professional production. In the future, the form factor of the camera will continue to evolve. Fortunately for the sound mixer, without quality audio, there is no quality picture.