Wednesday, September 19, 2012

Understanding F-Stop and Lens Speed


f-stop
The photographer adjusts the opening of the aperture by setting the f-stop. An f-stop is a ratio of the focal length of the lens to the diameter of the opening of the aperture. For example, a 50 mm lens with an aperture opened up to a diameter of 12.5 mm results in an f-stop of f4 (50 ÷ 12.5 = 4).
Therefore, the larger the numerical value of the f-stop, the smaller the opening of the aperture. The speed of a lens is determined by its largest f-stop value (smallest number). Thus, the larger the aperture, the faster the lens.



Understanding Lens Speed
A lens’s speed is determined by the maximum amount of light the lens is capable of transmitting—the largest f-stop value. When a lens is capable of transmitting more light than other lenses of the same focal length, that lens is referred to as fast. Fast lenses allow photographers to shoot at higher shutter speeds in low-light conditions. For example, lenses with maximum f-stop values between 1.0 and 2.8 are considered fast.

1 comment:

Sammy Jennings said...

A macro dslr camera lens will work great for product photography to capture tiny details with excellent focus. A wide-angle lens works well for landscapes because it can take it all in.