ISO

ISO governs the amplification of the signal (light) during digitization of light incident on the sensors.

Amount of light incident on a pixel will determine signal. Amplitude of that signal will determine its grayscale tonal value or (perceived) brightness or luminosity.

Higher ISO settings will not only amplify the signal but also noise.

Use higher ISO under the following conditions:

• Shooting in Av & need faster shutter speed

• Shooting in Tv & need larger DoF

• Not enough incident light, and need brighter image (at cost of more noise)

When shooting under difficult/low lighting conditions, choose largest aperture that will allow a fast shutter speed. Take a test shot. If the shutter speed is not fast enough to avoid any blur or shake, bump up ISO, to stop-down (or further increase) shutter speed.