Definitions for "LENS SPEED"
Keywords:  aperture, focal, widest, fast, slow
The widest possible aperture on a camera or lens. The wider it is, the faster a camera is said to be.
Refers the a lensâ€(tm)s ability to transmit light. Fast lenses transmit more light than slow lenses. Lens speed is calibrated in f-stops. Lower numbers (f/1.8, f/2.0) indicate faster lenses. Speed is a desirable quality because it allows the photographer to shoot in relatively low light
The largest lens opening, e.g. f2 not f16. A fast lens transmits more light and has a larger opening than a slow lens. (see f-stop & Slow lens)