Camera noise, or digital noise, is the result of the functions of a digital camera and can be caused by several factors. In low light and with high ISO settings, the digital noise will increase because of the increase in sensitivity of the digital sensor. Other factors include poor lens quality and thermal noise caused by heat from the sensor. In any case, noise can take an otherwise lovely image and make it a grainy mess. Reducing camera noise becomes a priority for any photographer who is working in a low-light situation, such as a wedding or event.
Update your camera's firmware. Most camera manufacturers have implemented some type of noise reduction software into their firmware package; having the latest version ensures the most up-to-date use of the camera's technology to combat digital camera noise. Updating the firmware varies, depending on the manufacturer.
Use a lower ISO setting. This may be done by decreasing the shutter speed or increasing the f-stop settings, allowing the photographer to use a lower ISO. A lower ISO means decreased sensitivity of the image sensor, and so smaller electrical currents--the cause of ISO related noise--are not recorded.
Use a high-quality lens, if possible, that allows for a wider aperture. This will allow more light to fall on the sensor and allow a decrease in ISO sensitivity, as above.
Use an on- or off-camera flash. Adjusting the lighting will allow the photographer to use a lower ISO. Better lighting equates to a better-quality image where digital photography is concerned.
Use photo-editing software to further smooth and refine the image. Once the image is taken, noise reduction is in the hands of the processing software. Adobe Photoshop has built-in noise reduction found under "Filters" and then "Noise" on the top toolbar. Additional, downloadable software such as Noise Ninja and Neat Image are also noise-reduction packages.