One of the first steps most people take to improve their camera’s audio is buying an external microphone. However, not all external camera mics make significant improvements in audio quality. Few improvements exist to increase a microphone’s ability to capture sound from a distance. An article from Shure said this,
“The reality is that microphones do not reach out and grab the sound from a distance. They merely measure pressure variations right at the diaphragm itself. The microphone doesn’t “know” anything about what is happening at any distance from itself. For this reason, if you try to characterize a microphone’s “reach”, it’s almost completely dependent on the ambient acoustic conditions around the microphone.”
Some microphones employ directionality to decrease the amount of sound entering from the sides and rear of the microphone. These typically have the advantage of decreasing the amount of undesired sound entering the microphone, by facing the null-point(s) of the microphone away from undesired sound sources. This said, the best microphones for capturing sound from a distance can be large and unwieldy, so camera-mounted mics strike a balance between audio quality and practicality.
While the right mic can improve audio quality for external camera-mounted microphones, there’s no substitute for getting closer to the sound source. For best results with any microphone, keep the subject within 3’ (1m) of the microphone and isolate the mic from loud, unwanted sound. If the subject requires a lot of distance, either get the mic off-camera and closer to the subject, or place a lavaliere mic on the subject or sound source. Microphones have physical limitations of acoustics and hardware, so if you’re getting poor audio results, try getting closer.
A Primer on Microphone Polar Patterns (skip this if you’re in a hurry)
Built-in Camera Microphones
Most modern DSLR, mirrorless, and smartphones cameras come equipped with a pair of microphones for stereo audio recording. These mics are almost always either omnidirectional or cardioid. These work surprisingly well for capturing sound in close proximity to the camera and for generally capturing the sound of the environment. Try speaking into your camera’s microphone while standing within 3’ (1m) in relatively quiet, indoor environment. The audio should sound very clear from all directions for omnidirectional microphones, and for cardioid microphones, it should sound clear directly in front of the lens.
Using an iPhone 11 or Samsung Galaxy Note 10? These smartphones come equipped with “Audio Zoom” that artificially isolates the sound in the camera’s field-of-view from sounds off-camera when shooting video. These devices (especially iPhone 11) and newer can work better than external microphones in some cases.
Most entry-level external camera microphones have a cardioid polar pattern that captures sound from the front of the microphone, and attenuates sound from the rear. These unidirectional microphones capture the widest pattern from the front, and provide a deep null from the rear.
The problem with camera-mounted cardioid microphones is that the lack of the narrowed directionality to capture sound from directly in front of the camera. They’re very sensitive to the ambient noise of the environment, including acoustical reflections from surrounding walls. Cardioid mics typically sound best well within 3 feet (1m) of the microphone, making them impractical for camera work. This can work for vlog-style video work when holding a camera at an arms-length, but rarely offers much improvement over the camera’s or smartphone’s built-in microphones. Unfortunately, external camera-mounted cardioid mics provide very little value. We recommend avoiding them altogether, unless of course, you plan on using them off-camera, close to the subject.
- Natural sound in quiet rooms with good acoustics
- Excellent off-axis rejection from the microphone rear
- Requires close proximity to the mic
- Offers little advantage over the camera’s built-in microphones
- Poorly suited for on-camera video use
Cardioid Microphone Variations – Supercardioid & Hypercardioid
Supercardioid and hypercardioid are modified cardioid mics that reject more sound from the sides at the cost of sacrificing some off-axis attenuation from the rear. These two polar patterns differ from a technical standpoint in that supercardioids provide roughly equal attenuation from the sides and rear of the mic, whereas hypercardioids provide more attenuation from the sides at the cost of less attenuation from the rear.
For use as camera-mounted mics, these are typically preferable to cardioid mics as the added attenuation from the sides of the mic helps to better isolate sound from directly in front of the camera from the sides. In practical terms, it’s difficult to distinguish between the two, although hypercardioid offers a slight advantage for on-camera use with its superior rejection of sound from the sides of the mic.
With the improved pickup from the rear of hypercardioid mics, they might seem like better options for vlogging where the person behind the camera occasionally speaks. However, the frequency-response of hypercardioid mics typically decreases from the rear of the mic, resulting in a slightly muffled sound. Sound behind the mic will be slightly more audible than with a cardioid mic, but won’t offer a true bidirectional response.
- Some are inexpensive
- Typically small and lightweight
- Good balance between attenuation from the sides and rear of the mic
- Slight improvement over most built-in camera mics
- Can be more expensive than cardioid mics
- More sensitive to sound from the rear than cardioid
Shotgun, or rifle microphones are commonly used in video production and filmmaking for their ability to reject some sound from the sides of the mic. As mentioned previously, shotgun mics have no better “reach” than mics with other patterns, but can offer better results in some situations. As an article from Sound On Sound points out, all shotgun mics use a common directional capsule with an “interference tube” that intercepts incoming off-axis, high-frequency sound. In essence, these mics offer some slight directionality over supercardioid and hypercardioid mics, but off-axis attenuation decreases substantially at lower frequencies. This means shotgun mics only block high-frequency sound from the sides of the mic when compared to supercardioid and hypercardioid mics, although the length of the microphone barrel makes a difference how it well blocks off-axis sound, and at which frequencies.
Longer microphone barrels offer better off-axis “interference”, whereas short barrel shotgun mics offer little to no advantage over supercardioid and hypercardioid designs. In fact, the microphone element in short barrel shotgun mics can have more noise, since more sound pressure is required to reach the microphone element through the tube.
Shotgun microphones are generally superior to built-in camera mics and standard cardioid camera-mounted mics, but aren’t worth the premium price over supercardioid or hypercardioid designs. This said, feel free to use a shotgun microphone if you have access to one. Many on the market come with handy accessories, such as shock mount to reduce vibration noise, or a windscreen kit for use outdoors. The benefit of the accessories from shotgun mics, commonly marketed for video use, can make it more practical than a mic with slightly better specifications.
- Fairly lightweight
- Good off-axis rejection, esp. at high frequencies
- Preferable to built-in camera mics
- May come with useful accessories like a shock mounts and windscreen
- Can be expensive
- Can be long and unwieldy
- Short shotgun mics offer little benefit over supercardioid and hypercardioid mics
- Off-axis frequency response can be inconsistent
Windy environments necessitate the use of a windscreen, or material to shield the microphone from low-frequency wind noise. These are almost always necessary outdoors, and occasionally indoors near fans and HVAC systems. Greater amounts of wind require more material for shielding, sometimes requiring the use of more dense materials, like a “dead cat” windscreen to block incoming wind noise. External microphones offer the advantage over built-in camera mics by allowing for the use of a windscreen to block wind turbulence against the microphone.
More dense windscreen material attenuates high-frequency content, and may result in a slight “muffled” quality to the resulting sound. Moreover, a bulky windscreen may interfere with camera operation, potentially obscuring the camera lens. Most manufacturers of external on-camera mics offer windscreens designed to fit over the microphone easily with minimal sound coloration. If planning to use outdoors, opt for a microphone that comes equipped with several densities of windscreens that won’t interfere with camera operation.
Externally mounted camera mics can offer some benefit over built-in camera microphones, but still have limitations due to their size and inability to capture sound from a distance. When opting for an on-camera microphone, it’s best to choose a supercardioid or hypercardioid design, as these provide the best combination of size and directionality. Short shotgun mics offer little improvement over cardioid designs, and longer shotgun designs can be unwieldy and impractical to use as a camera-mounted mic.
External camera mics offer the advantage of using windscreens, making them more suitable for outdoor use than built-in camera mics. Windscreens block incoming low-frequency wind noise from entering the microphones at the cost of slight high-frequency attenuation. Choose a microphone with a windscreen that won’t be so large as to interfere with camera operation.
We hope this helps you narrow down your selection for choosing an external camera-mounted microphone. Keep in mind that getting closer to the sound source is one of the easiest ways to improve audio quality. If you can’t use a lavaliere or get the microphone off-camera, the right microphone can offer some improvements to your audio for video.
If you found this helpful or would like to share your thoughts, let us know in the comments below.