Magic Triangle of Photography: Aperture, ISO and Shutter Speed

by Enche Tjin on June 18, 2009

They key to correctly exposure photos depends on three magic triangle of photography are aperture, shutter speed and ISO. The combination of these factors make up for the optimal exposure for any situations.

Aperture is is the opening in your camera lens through which you let in light. So if you are in an area with strong light, you can let in less light through the lens. If it’s dark, you can have a high aperture to let in more light. The numbers goes the other way here! A high number means you are letting in less light, and a low number is to let in more light.

Aperture is also used to control depth of field. Big aperture create shallow depth of field and vice versa.

Aperture usually ranges from small opening with the number 22 and all the way down to a big opening with the number 1. Each lens has different maximum and minum aperture.

Shutter speed is the length of time your camera lets in light. This measures in seconds, or parts of a second, usually from 1/4000 of a second all the way up to 30 seconds. Shutter speed range depends on camera body instead of the lens.

Shutter speed affects the image in two ways. High shutter speed freezes the motion, slow shutter speed captures streaming motion.

ISO is a measurement which applies to film and represents the films sensitivity to light. It can go as low as 50, and keeps doubling up (next is 100, then 200, continuing to 400 etc) and reaches very high numbers. Low ISO is less sensitive to light. High ISO is more sensitive to light.

High ISO will degrade image quality. The image will appear noisy or grainy and details might be loss. But in low light situation, many times high ISO is needed.

By playing around with these three basic settings in your camera, you will be able to make bright areas look dark and dark areas look bright and everything in between.

For better understanding, I recommend to read Understanding Exposure by Bryan Peterson

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