Assessing Visual Noise Produced with Regular Screens, Random Screens, and Screenless Techniques

The new non-regular screens, especially FM screens, produce a problem which has been unknown with regular screen, i.e. the phenomenon of graininess or visual noise. Dependent on the screening algorithm noise can be stronger or weaker leading to the question as to which noise level is acceptable for prints. A comparison is made between prints produced with the following processes: FM screens (Velvet, Cristal, Diamond, Scitex), regular screens, random screens, screenless techniques, and Collotype. The visual noise is assessed by image analysis. It is shown that a distinction has to be made between blue noise and white noise, the latter being the far more objectionable form.