Understanding Noise

Have you ever noticed countless tiny colored dots in your photographs? If you have, it’s probably because you have (consciously or not) forced your camera into becoming more sensitive to light. That feature or decision is managed via the ISO settings, because aperture is responsible for the amount of light hitting the sensor, and shutter speed determines how long light actually hits the sensor. ISO is the main reason for noise in our photographs, and today we’ll talk about how to reduce it. There are ways to achieve this in-camera and in post-processing. But first, let’s define the difference between noise and grain, and how noise actually increases in our photographs.

Grain ≠ Noise

Unlike grain in film, noise is an undesired artifact created when we increase our camera’s sensitivity to light by increasing the ISO (100, 200, 400, 800, 1600, 3200, 6400, and beyond). Film is manufactured by incorporating light-sensitive silver bromide crystals in very thin layers of gelatin. These light- sensitive crystals have pretty much the same “amount of sensitivity” but are embedded in different sizes. Finer crystals are used for less-sensitive films, and rougher ones for high-speed films. When light hits these crystals, they get dark and an image is captured. That’s where graininess comes from, but it has a certain appeal. It is even desired by some film photographers. It imparts a gritty, rough look that is very appropriate to certain situations, like war or boxing.