Photography - Exposure

SHUTTER SPEED

A camera's shutter determines when the camera sensor will be open or closed to incoming light from the camera lens. The shutter speed specifically refers to how long this light is permitted to enter the camera. "Shutter speed" and "exposure time" refer to the same concept, where a faster shutter speed means a shorter exposure time. Controls the duration of exposure.

Shutter Speed	Typical Examples
1 - 30+ seconds	Specialty night and low-light photos on a tripod
2 - 1/2 second	To add a silky look to flowing water Landscape photos on a tripod for enhanced depth of field
1/2 to 1/30 second	To add motion blur to the background of a moving subject Carefully taken hand-held photos with stabilization
1/50 - 1/100 second	Typical hand-held photos without substantial zoom
1/250 - 1/500 second	To freeze everyday sports/action subject movement Hand-held photos with substantial zoom (telephoto lens)
1/1000 - 1/4000 second	To freeze extremely fast, up-close subject motion

APERTURE SETTING

A camera's aperture setting controls the area over which light can pass through your camera lens It is specified in terms of an f-stop value, which can at times be counter intuitive, because the area of the opening increases as the f-stop decreases. In photographer slang, when someone says they are "stopping down" or "opening up" their lens, they are referring to increasing and decreasing the f-stop value, respectively.

By the Numbers. Every time the f-stop value halves, the light-collecting area quadruples. There's a formula for this, but most photographers just memorize the f-stop numbers that correspond to each doubling/halving of light:

Aperture Setting	Relative Light	Example Shutter Speed
f/22	1X	16 seconds
f/16	2X	8 seconds
f/11	4X	4 seconds
f/8.0	8X	2 seconds
f/5.6	16X	1 second
f/4.0	32X	1/2 second
f/2.8	64X	1/4 second
f/2.0	128X	1/8 second
f/1.4	256X	1/15 second

ISO SPEED

The ISO speed determines how sensitive the camera is to incoming light. Similar to shutter speed, it also correlates 1:1 with how much the exposure increases or decreases. Common ISO speeds include 100, 200, 400 and 800, although many cameras also permit lower or higher values. With compact cameras, an ISO speed in the range of 50-200 generally produces acceptably low image noise, whereas with digital SLR cameras, a range of 50-800 (or higher) is often acceptable.