ISO, Shutter Speed & Aperture Definitions

ISO

ISO is the level of sensitivity of your camera to light. The lower that the ISO is the less sensitive your camera is to light, whereas the higher the ISO the more sensitive it will be to light. A lower ISO (100 – 400) works best in high key lighting situations while higher ISO settings (3200 – 6400) work better in situations where there is low key lighting.  The ISO also has no effect on the amount of blur that will be caused when moving it, so it is good to use a higher ISO instead of a lower shutter speed when in dark areas if you don’t have a tripod or anything to put the camera on to keep it steady.

Shutter Speed

High ISO can cause noise and a grainer image quality, so in some cases it would be better to use a lower shutter speed given that you have a tripod or something to support the camera, since lower shutter speed can cause more blur if moved even slightly. For handheld you should never use a shutter speed lower than 1 / 60th. Lower shutter speed also has no effect on image quality, only lighting, so there well be no noise or graininess on the photograph. Also, a higher shutter speed lets less light in, while a lower one lets more light in. A very high shutter speed like 1 / 1000th is also used to freeze action.

Aperture

Aperture is a hole within the lens which lets light travel through into the camera body – the size of this hole controls the amount of light let through and the depth of field.  Depth of field is what controls what is in focus and what is blurred. A small aperture (f22 – f11) means that the depth of field will be large and a large (f2.8 – f5.6) aperture means the depth of field will be small. A larger aperture also lets more light in, while a smaller aperture lets less light in. A small aperture is useful in high light situations in which you want only the image in the foreground to be in focus. Using a large aperture in high key lighting situations means the image can be under exposed, but the entire image will be in focus. If you want to use a larger aperture in high key lighting situations you should lower the ISO, or lower the shutter speed if you have a tripod.