Noise in digital photographs is the visual equivalent of static. Most digital cameras add some level of noise to images. In traditional photography the nearest equivalent is film grain. Digital noise is noticeable in high ISOs and is more visible in areas of uniform color, such as skies and shadows.
Digital sensor noise may also be increased during long exposures in low light. Noise or color film grain is more obvious in areas of underexposure, while black-and-white film exhibits more grain during overexposure.
You can minimize noise by using low ISO settings, faster shutter speeds, and making sure you have the proper exposure but if noise is still a problem, sometimes digital noise reduction software is the solution. There are lots of noise reduction products available for Mac OS and Windows computers, and I've tested many of them. Here's my (very) short list:
Neat Image (Stand-alone pplication or Photoshop plug-in) creates uses profiles to adapt noise reduction to your specific imaging device. A device noise profile is a reusable analysis of noise properties of a digital camera or film scanner; Neat Image automatically selects the best matching profile using the file's EXIF data. (Or, you can manually select the desired profile). Mac/Windows. Home version: $34.90; Pro version (supports 24- and 48-bit images and works with Photoshop Actions): $59.90.
Imagenomic's Noiseware removes high and low ISO noise and JPEG compression artifacts from digital image files as well as grain from scanned film. The interface is intuitive and you'll get superb results without reading the Help file. Noiseware's self-learning mechanism automatically calibrates a noise profile and chooses optimal noise removal settings without requiring camera-specific profiles. Mac/Windows. Photoshop-compatible plug-in or standalone program. ©2007 Joe Farace
Be sure to download a demo and try for yourself before buying!
Joe Farace is the author of a new book called “Getting Started in Digital Imaging” published by Focal Press (ISBN 024080838X.) It's available in all the best bookstores as well as Amazon.com.