Various sophisticated software packages are available to remove or reduce noise produced by sensors in images. Noise generated by CCDs has two parts, luminance noise and chroma noise. Luminance (brightness) noise makes an image look grainy on screen, but may not be visible when an image is printed. Chroma noise is visible, at least when images are closely examined at pixel level, as random red and blue pixels. It is normally less obvious than luminance noise both on screen and when printed.

Removing luminance noise inevitably reduces the sharpness of an image to some extent. Removing chroma noise damages the colour content of an image to a small degree. Noise reduction is therefore a compromise between increasing image softness and the extent of acceptable color damage against the degree of noise removal achieved.

A number of excellent noise reduction programs are available - some as Adobe Photoshop plug-ins and some as stand-alone software. Among the better tools are:

• Neat Image;
• Noise Ninja; and
• Noiseware.