Camera Exposure

Exposure Triangle: Aperture, ISO & Shutter Speed

Each setting controls exposure differently:

Aperture: controls the area over which light can enter your camera
Shutter speed: controls the duration of the exposure
ISO speed: controls the sensitivity of your camera's sensor to a given amount of light

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.

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

ISO SPEED

       ISO speed is the measure of a digital imaging sensor’s sensitivity to light. The ISO speed setting can be changed in most Digital SLR cameras in order to increase or decrease its sensitivity to light. When photographing in low light conditions such as inside a church or an indoor sports stadium where flash photography may not be permitted, a photographer is faced with a situation where even at the largest aperture setting the shutter speed is too low to get sharp pictures of moving subjects. In order to obtain the correct exposure at a faster shutter speed the sensitivity (or ISO speed) of the camera’s sensor can be increased. Higher ISO speeds introduce noise (grain) in the picture and are therefore considered a last resort. Some photographers use grain as an artistic tool for incorporating emotions, introducing moods or for achieving specialty looks in their pictures. General rule of the thumb when setting ISO speed is to choose the lowest possible ISO speed at which proper exposure can be achieved at a shutter speed that is fast enough to take sharp pictures of your subject.