Randomly-spaced speckles, called noise, can appear in digital images. Noise is similar to grain that appears in photos taken with traditional cameras using high ISO films.
Noise increases in photos taken with a digital camera using a high ISO number, usually over ISO 100. The higher the number, the more noise.
When noise is present, image detail and clarity are reduced, sometimes significantly. Noise is most noticeable in even areas of color such as shadows and in a sky.
Noise is especially visible when viewing a photo at 100% on a computer monitor. But when the image is reduced in size, noise may be barely visible. In fact, it may not be noticeable at all in small sized prints. The exception is when a very high ISO setting is used.
The good news is that there are steps to minimize, if not prevent, noise. There are also special software programs that do an effective job at noise reduction.
If you keep your digital camera set to ISO 100 or below, you’ll rarely have problems with noise. The most notable exception is when there are dark, murky areas in a scene.
If you take a lot of low light photos, consider getting a digital single lens reflex camera. DSLRs have large sensors and produce very little noise compared to the vast majority of compacts, which have small sensors and limited light sensitivity. However, some newer compact digital cameras have better high ISO performance such as the Canon s90.
Shooting in low light
Using a flash can help prevent image noise if you stay within the recommended flash range for a camera. If you prefer not to use the flash, increase room lighting. Let outside light into the room through doors and windows. Turn on more room lights but also select an appropriate white balance setting.
If possible, use a tripod or other support such as a table top, to keep the camera steady rather than raise the ISO.
In-camera noise reduction
Some digital cameras include a Noise Reduction setting. When the setting is enabled, noise reduction takes place whenever shots are taken at very slow shutter speeds. While noise reduction works, some digital cameras do a better job of it than others. When a large amount of noise appears in an image, detail will be smeared.
It should be pointed out to DSLR users that in-camera noise reduction my interfere with some camera functions, such as significantly slowing burst mode.
Shooting at very high ISO numbers
Some consumer digital cameras have a high sensitivity mode, or the capability of shooting at ISO 800, 1600 and higher. The quality of images produced using high ISO can be significantly degraded unless you have a camera capable of handling it well.
Test your digital camera to see the highest ISO number and the amount of noise it produces that you can tolerate.