Convergence in Broadcast and Communications Media

4Sampling

 

 

4.1 Introduction

Sampling is a process of periodic measurement which can take place in space or time and in several dimensions at once. Figure 4.1(a) shows that in temporal sampling the frequency of the signal to be sampled and the sampling rate Fs are measured in Hertz (Hz), the standard unit of temporal frequency. In still images such as photographs there is no temporal change and Figure 4.1(b) shows that the sampling is spatial. The sampling rate is now a spatial frequency. The absolute unit of spatial frequency is cycles-per-metre, although for imaging purposes cycles-permillimetre is more practical.

If the human viewer is considered, none of these units is useful because they don’t take into account the viewing distance. The ...