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AM/FM Hybrid Screening

SPEKTA screening
SPEKTA uses AM-like dots or FM-like dots depending on the colour-density qualities of each image. By doing this it overcomes the weaknesses and delivers the strengths of both screening methods.

In the 1-10% highlights and the 90-99% shadows, SPEKTA uses FM screening's fixed dot size and reproduces tone by varying the density of these uniform dots. In the 10-90% midtones, it varies the size of the dots just as AM screening does. However, the placement of dots is always random as in FM screening, so there are never any screen angles to contend with.

Highlight and shadow areas
SPEKTA uses FM-like dots for highlight and shadow areas. Dots are distributed randomly and their size is also varied to produce tonal gradations. The distribution of the dots is optimised to ensure that they don't overlap or leave large gaps. In this way, graininess is kept completely under control.

Midtone areas
For midtone areas, although SPEKTA distributes the dots randomly as in FM screening, the tonal reproduction is more like conventional AM screening. That is, while maintaining a fixed number of dots, tone is reproduced by varying the size of the dots. These dots have an optimised roundness that makes them very easy to print. Measures are also introduced that prevent dots toward the highlight range from overlapping. This solves the problem of graininess, which can occur when the gaps between dots vary.