iStock - Stock Video Training Manual

6.5 - Digital Video Requirements: Noise and Compression

Digital Noise & Color Distortion:

Picture noise is the variation of values in the detection process of your camera. Noise and color distortion (or digital noise) occurs most frequently in uniform color areas (i.e. skies and shadows), particularly in low light situations. Noise can be avoided by switching off the gain function of the camera, opening the iris, or adding light to the scene.

Compression noise is identified by pixilation of the image. It occurs when the video compression circuitry in the camera cannot keep up with the complexity of a moving image. Compression noise can be avoided by limiting the amount of rapidly moving pixels in the frame. A tree in a windstorm may be fine, but if it also involves a snowstorm, and you’re shooting handheld, there will almost certainly be compression noise.

Compression:

The PHOTO JPEG (or Motion JPEG-A or Motion JPEG-B if interlaced) file format uses a "lossy" compression method, meaning that in order to make the file smaller, information is thrown away, or lost. The "quality" setting that most clip editing programs and digital cameras have when saving Photo/Motion JPEG determines how much information is lost. At a certain point, with lower quality settings, the removal of information during the compression process can become visible in the form of compression artifacts (places in the clip where too much detail has been lost). Too much Motion JPEG compression can become visible either in the form of a general loss of detail, or grainy/patterned areas (especially in flat spaces, such as skies). Set your output/render queue to HIGH or BEST when outputting final video. Avoid re-saving or re-rendering Photo or Motion JPEG video as the clip will degrade quickly with each render.

Previous | Next

Not a member?Join
Cart (0)