Noise - What is Noise in a Digital Camera?

Noise in a digital camera is that often annoying grainy look that makes your photos seem like they were shot in a dust storm or printed on an old dot matrix printer. Many a fabulous shot has been ruined by excessive noise in the picture.

What is Noise?
Noise in a digital camera is the equivalent of what we called grain in film cameras. This is similar to color noise although the visual result is somewhat different.

What Causes Noise?
Noise is caused by the digital sensor attempting to record tiny amounts of light. Basically the camera is trying to record what is too dark to record and as a result any stray electrical signals wind up on the finished picture as flecks, or noise. The faster ISO you set on your digital camera, the more noise increases as it picks up smaller and smaller electrical signals.

Why Does One Camera Have More Noise Than Another?
Digital cameras convert light into electricity and then that electricity is converted into pixels. Each camera manufacturer uses different sensor chips and software to handle these conversions. As such, some cameras are better at reducing noise than others. In addition to software, the size of the sensor itself and the number of pixels on that sensor can affect the amount of noise and how big the flecks are when noise does occur.

How Can I Reduce Noise?
You can reduce noise, or at least the appearance of noise in your digital photographs. The most common way is to shoot at a lower ISO, generally 800 or lower. If you must shoot with a higher ISO, overexpose the image if possible (even if it means moving up one more ISO setting). Because noise often shows up as bright flecks, you can reduce the effective appearance of them by slightly overexposing your picture and correcting in post processing. If you underexpose you will brighten the noise as you brighten the picture in post processing.