By Adrian Toon, director of a2n.
What is a noisy picture? It’s nothing to do with what you are taking a picture of or its composition; it is a measure of ‘graininess’ in the final image. All cameras capture ‘noise’ in the images they take, so what is it and how do we reduce it?
There are broadly two types of noise: ‘shot’ noise and ‘digital’ noise. Shot, or photon, noise we can do little about as it is the randomness of the photons in any scene we are trying to capture. Digital noise on the other hand, is generated by the camera’s sensor and the internal electronics in the camera. Both produce similar noise in our pictures.
We can reduce digital noise by purchasing a good quality camera, but at very high sensor speeds (ie, very low light), noise will still become an issue. So, what can we do to minimise noise?
Most or you will have heard of ‘signal to noise ratio’ on various equipment, and this is what we must improve for our images. As noise is present in every image, the more signal we can get over the noise will improve our picture. Signal in our case is increased with capturing more luminance or light in our image.
We achieve this in a camera by choosing a well-lit subject or, if that is not possible, by trying to get as much light on the sensor as possible by using a larger aperture (lens opening) or longer exposure (longer time and use of tripod).
For those of you are using DSLRs, quality compacts or opting to use your phone cameras now in manual mode, possibly capturing RAW images can hopefully reduce the appearance of ‘noise’ and further improve your photography.