Monday, 20 August 2012

What is a Fast Lens?

A fast lens is one which has a low f-stop rating. In other terms the larger the aperture, the faster the lens. The amount of light that reaches the camera sensor is controlled by the aperture of the lens. And a lens with a smaller f-stop value / larger maximum aperture lets in more light to the camera sensor and as a result the camera could achieve faster shutter speeds for the given lighting conditions and hence called a fast lens.

Canon 50mm f/1.2 L IS USM
Canon 50mm f/1.2 L IS USM

Simply put a fast lens is one which has a larger aperture rating and not one that focuses fast.

Generally when we say fast lenses we mention to lenses that have their f-stops in the range of f/1.2, f/1.4 and f/1.8. but depending upon the type of the lens any lens which has an aperture rating of f/2.8 or below could be called a fast lens.