Digital Noise

Digital Noise - What Is It? What Causes It? And How Can I Get Rid Of It?
By Ziv Haparnas

Digital noise in photos taken with digital cameras is random pixels scattered all over the photo. It is a similar effect as “grain” in film photography and it degrades the photo quality.

Digital noise usually occurs when you take low light photos (such as night photos or indoor dark scenes) or you use very slow shutter speeds or very high sensitivity modes.

When taking pictures with a digital camera an electronic sensor (also known as a CCD) built from many tiny pixels is used to measure the light for each pixel. The result is a matrix of pixels that represent the photo.

As with any other electronic sensor the CCD is not perfect and includes some noise (also know as white noise to hint on its randomness attribute). In most lighting the light is significantly stronger than the noise. However in extreme scenes where the light is very low or when a high amplification is needed noise levels can become significant and result in pixels in the photos that include more noise data than real photo light data. Those pixels usually appear as random dots or stains on the photo (for example white dots scattered randomly on the photo).

Understanding digital noise in various scenes:

low light (night photos or dark scenes): when the scene is dark the amount of light measured by each pixel of the CCD is low. When the light intensity is very low it can become too close to the level of noise naturally found in the CCD. In such cases some pixels can appear as noise because the noise level measured for them is significantly close or higher than the actual light intensity.