Digital Camera World - UK (2019-12)

54 DIGITAL CAMERA^ DECEMBER 2019 http://www.digitalcameraworld.com

Camera

College

What is noise all about?

You can improve the quality of your pictures by reducing the amount of image

noise. But what causes it, and how exactly do you keep the noise down?

Noise is a generic term

used to describe a

disturbance to an electrical

signal. Often irregular and

always unwanted, it is

generated by all electronic

devices and takes on a variety

of forms – from the ‘hiss’

of audio equipment to a

pixellating television display.

While discussions about

sources of noise can get very

deep and technical, its effects

are obvious when it comes to

digital photography. Broadly

speaking, noise is similar to film

grain in that it can obscure fine

details and it gets progressively

worse as the ISO is increased.

But where grain can add to the

mood of a picture, noise can

simply leave you in an ugly

mood, such is its rather artificial

look. It manifests itself in a

number of ways, including a

curtain of dots across an image,

clusters of coloured speckles,

and horizontal and vertical

coloured banding. Your mileage

may vary over how much it

bothers you: noise may be

acceptable in an action-packed

sports shot taken at night, for

instance, but a complete

turn-off when it comes to

a detailed macro image.

The key factor when it comes to

noise is the signal-to-noise ratio

(SNR). When the ‘signal’ – the

intensity of light captured by the

camera’s sensor in our case – is

greater than the background

noise generated by the

electronic circuitry, the image

will show little interference.

When the SNR is weaker,

however, it is harder to

differentiate the noise and

the image information.

There are several factors

that can raise the level of noise

to the point where it has a

detrimental effect on the

Brightening up shadow details in software can exacerbate noise, although this can be remedied with noise reduction.

Marcus

Hawkins

Photographer and

writer Marcus is a

former editor of

Digital Camera

The complete guide to modern photography

WITH NOISE REDUCTION

UNPROCESSED IMAGE