Stock Photography Resources
Noise in Digital Images
Sometimes images are described as being "noisy" or having too much noise. Usually noise is undetected in digital images as we view them on our computers. It is not until they are viewed at 100% in a photo processing program or printed in a large format that the noise will be observed.
It appears as random speckles, usually in the darker areas of the image, but it can appear in any part of an image depending on a variety of shooting conditions and camera settings.
Digital noise is often compared to film "grain" in the days of shooting with rolls of film. The higher the ISO of the film, (ISO 100, 200, 400, 800) the grainer the printed image. The same is true of the digital cameras of today. The higher the ISO setting on the camera, the more noise the image will have. Even the higher-end DSLR cameras produce noise at the 800-1600 ISO settings.
If noise is like grain in film photography, then why is it so undesirable in digital photography. Unlike grain, noise degrades the quality of the image, making smooth surfaces appear speckled and blotchy. Grain gives an artsy or old-fashioned appearance across the entire image. Noise adds colored speckles that detract from the image, often more noticeable in certain areas, not the entire image.
It is best to avoid the conditions that create the noise when you are composing the image. Avoid using high ISO settings, and trying to get the exposure correct will help quite a bit. One thing that most photographers don't think about is the heat that the sensor creates when the camera is on. This heat also creates digital noise. This is unavoidable in the summer months and when taking a long exposure that keeps the sensor working longer.
Since some of these conditions are beyond the photographer's control, several companies have created software that removes the digital noise from photos. This sounds like the perfect answer to this digital noise problem, and it can be once you get the hang of using the software.
The biggest drawback of these noise removal tools is that the image quality will suffer and the photo will develop a softer edge. If the process is used too heavily, image detail is lost and the objects take on a plastic, unnatural appearance.
I have posted the links to a couple of sites that explain what noise is and how to deal with it. Take a look at the before and after images on these sites to familiarize yourself with how to recognize noise in your images.
Some of the microstock sites are very strict on noise and will not tolerate it. Viewing your images at 100% in your photo processing software will help you recognize the noise and artifacts that can plague your images.
Tutorials by Cambridge in Color has a two part tutorial dedicated to digital noise. There are also many other tutorials on this site that have some great information.What Is... Noise? discusses sensors and how their size relates to digital noise.
Digital Imaging Noise a short article describing the cause and effect of digital noise.