There are two basic pickup patterns for microphones - nondirectional (omnidirectional) and directional. Omnidirectional microphones pick up sound from all directions and are best for most applications, if there are no environmental problems (noise, feedback from speakers,etc.) Omnidirectional microphones offer widest, smoothest response for a given price, and lower sensitivity to breath, wind, and handling noises.
Omnidirectional microphones pick up sound, from all directions and are least sensitive to breath, wind, and handling noise. "Shaped-response" omnidirectional microphones have a slight rise in the high-frequency response which provides increased voice intelligibility and a contoured low frequency rolloff to reduce handling and wind noise. This is useful for general-purpose ENG work where it is important to capture ambient sound in the background and with clear voice reproduction up front. This can be desirable for vocal use by entertainers. The disadvantage is a need to maintain a fixed working distance for consistent sound quality.
Directional microphones pick up sounds primarily from one direction or area and should be used where there are environmental noise problems, where maximum gain-before-feedback is required, or where there are great distances from microphone to sound source.
The three basic types of directional microphone patterns are cardioid, super-cardioid and hyper-cardioid which offer increasingly directional pickup.
Cardioid microphones are unidirectional in the sense that they are most sensitive to sound from the front of the microphone, and attenuate
sound to the sides and rear relative to the front. Traditional cardioid microphones are designed with one rear port opening at the back of the diaphragm. At close working distances the bass frequency response is boosted greatly. This is known as proximity effect.
Supercardioid microphones have slightly tighter patterns, and are useful in multiple microphone situations where pickup of adjacent sound sources is a problem.
Hypercardioid mikes have an extremely focused pick up pattern. This is where the name "shotgun" derives from. Good for long reach and selective miking.
Other Types of Directional Microphones include:
bidirectional (figure eight)
X and Y stereo (discreet left and right pickups)
M-S stereo (mid and side), (mid - side) are matrixed to create Left and Right channels.
Stereo spread can be controlled in post, but matrixing requires special decoders and may cause complications.