In digital television, analog original pictures are converted to digits: a continuous range of luminance and chrominance values is translated into a range of finite numbers. While some analog values will correspond exactly to numbers, inevitably others will fall in between. Given that there will always be some degree of noise in the original analog signal the numbers may dither by one Least Significant Bit (LSB) between the two nearest values. This has the advantage of providing a means by which the digital system can describe analog values between LSBs to give a very accurate digital rendition of the analog world.

If an image is produced by a computer, or is the result of digital processing, it may have virtually no noise and so the digital dither may not exist – which can lead to contouring effects. One approach to cure this is to use greater bit depth, eg 10 bits instead of 8, this will reduce the size of the problem but may not solve it. Another approach is offered with Dynamic Rounding. Invented by Quantel, this can intelligently add dither to pictures to give more accurate, better looking results.