Over sampling

Sampling information at a higher resolution than is required for the output format. For example, an HD picture can be regarded as an over sampled version of SD. SD pictures created from down sized HD are generally clearer, cleaner (lower noise) and sharper than those made directly in SD. This is because the size reduction process tends to lower noise and the output pictures are derived from more information than is available in a direct SD scan. An increasing amount of SD material is originated this way. Similarly, 35 mm film provides an over sampled source for SD and HD.