Buffer Depth
The number of consecutive frames a camera can shoot at full speed before its internal memory fills and the rate collapses.
Measured in
frames
In depth
The buffer absorbs images faster than the card can write them, so depth depends on file size, card speed and compression setting. Once full, the camera slows to the card's sustained write rate, which can be a quarter of the burst speed. For sports this matters more than the headline frame rate, since a full buffer at the wrong moment means missing the goal.
Examples in practice
A body rated at 200 raw frames of buffer covers a ten-second burst at 20 fps; one rated at 25 stalls after a second and a half.