Comparing Sampling Schemes for Photographic Images

image

resolution

40

50

60

70

80

sampling method

ordered

random

distortion

0.01

0.1

0.25

0.5

1

show mesh

show sample points

Hover over the image to see the original.

For printing or otherwise rendering a continuous-tone photograph, the number of tones needs to be reduced. This limited number of discrete tone levels is obtained by using a sampling scheme.

For any sampling scheme, there is a conflict between ordering (to get complete coverage) and randomness (to avoid aliasing or moiré patterns).

This Demonstration compares two types of random variation on an orderly scheme:

1. a perfectly ordered scheme with added random distortion

2. a sampling of random points nearest to an ordered raster