It is difficult to take good pictures without having a solid understanding of ISO, Shutter Speed and Aperture – the Three Kings of Photography, also known as the “Exposure Triangle”. While most new DSLRs have “Auto” modes that automatically pick the right shutter speed, aperture and even ISO for your exposure, using an Auto mode puts limits on what you can achieve with your camera. In many cases, the camera has to guess what the right exposure should be by evaluating the amount of light that passes through the lens. Thoroughly understanding how ISO, shutter speed and aperture work together allows photographers to fully take charge of the situation by manually controlling the camera. Knowing how to adjust the settings of the camera when needed, helps to get the best out of your camera and push it to its limits to take great photographs.
It is challenging to take good pictures without a good understanding of how ISO works and what it does. Camera ISO is one of the three pillars of photography (the other two being Aperture and Shutter Speed) and every photographer should thoroughly understand it, to get the most out of their equipment. Since this article is for beginners in photography, I will try to explain ISO as simple as I can.
Before we go any further, you should first understand how DSLR cameras work.
1) What is ISO?
In very basic terms, ISO is the level of sensitivity of your camera to available light. The lower the ISO number, the less sensitive it is to the light, while a higher ISO number increases the sensitivity of your camera. The component within your camera that can change sensitivity is called “image sensor” or simply “sensor”. It is the most important (and most expensive) part of a camera and it is responsible for gathering light and transforming it into an image. With increased sensitivity, your camera sensor can capture images in low-light environments without having to use a flash. But higher sensitivity comes at an expense – it adds grain or “noise” to the pictures.
Take a look at the following picture (click to open a larger version):