Image Capture Noise

Unwanted patterns can result from several sources, with one of the most common being the noise added during digital image capture. Images can be captured digitally by using either a scanner or a digital camera. This digitizing process not only captures the image data but also adds non-image data to the captured image.

Light-sensitive semiconductor capturing chips, either a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), that are used in scanners and digital cameras are responsible for adding most of this kind of noise. Lower-quality chips have lower signal-tonoise ratios—that is, they add more noise to images than higher-quality chips do. In addition, forcing a digital camera to capture an image faster or at a higher speed, known as pushing (raising) the ISO or capture speed, will also add more noise to an image. The higher the ISO used by a capture device, the greater the amount of noise added. One additional characteristic of noise is that it often tends to occur on certain channels more than others. This knowledge provides us with the opportunity to concentrate noise reduction efforts on the noisier channels.