With AM screening, the most widely used form of screening today, the position and angle of dots remains fixed, but the size of each dot is varied to reproduce the effect of continuous tone.
On the other hand, FM screening (or stochastic screening) uses dots of the same size, but places them randomly in varying amounts to reproduce continuous tone.
With the FM method, it is possible to produce very fine detailed print and eliminate the moiré and broken lines associated with AM screening.
With SPEKTA screening, you can have the best of both AM and FM screening methods. And you can have it on every page and every image that you print.
With SPEKTA, the quality that can be achieved with an ordinary setup of 175 lpi and 2,400 dpi will appear equal to that of 300 lpi printing. And it can achieve this without the stringent controls usually required for high lpi printing.
Higher quality print is achieved with the same printing equipment.
The placement of dots is always random with SPEKTA, as in FM screening, which means there are no screen angles to contend with. As a result, SPEKTA avoids the moiré resulting from interference patterns between screen angles and items such as lace cloth, stereo speaker mesh, and CRT screenshots.
It also eliminates the rosette moiré that can occur in dark gray or black areas.
SPEKTA does a better job of bringing out the vibrancy in the midtones for skin colours and other areas where true-to-life colour is required.
Photo images of fresh flowers and fruit, sumptuous meals and desserts it is easier than ever to reproduce the full appeal of these in print with SPEKTA.
SPEKTA demonstrates its superiority in reproducing fine details, such as those required in maps. It improves the rendition of lines that are created with halftones.
Because 175lpi AM screening tends to leave light-coloured fine lines jagged and broken, printers must often resort to using spot colours to reproduce them.
However, SPEKTA can reproduce these kinds of images sharply using only process colours.
Details such as fine hair and delicate lace are also rendered precisely, without jagged edges.
SPEKTA is supported by Screen's PlateRite series of thermal platesetters.
The extremely sharp dots achieved by PlateRite platesetters enable SPEKTA to produce hybrid screens of the maximum effectiveness.
RIPs that support SPEKTA are the HQ-510PC series RIPs, the digital workflow automation system, TaigaSPACE, and the intelligent RIP system for network production, Trueflow.
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.
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.
Great attention has been paid to the size of the smallest dot.
For a usual output device at 2,400 dpi, the smallest dot is about 10.5 microns (i.e. 1/2,400th of an inch).
Although dots of this size can be exposed to the plate, it is often impractical to print with them.
Precisely because they are very small, they tend to increase instability on press and pose the risk of problems occurring in highlight areas. SPEKTA eliminates this risk by making combinations of the smallest dots.
It combines two or three of these microdots (10.5microns) to build larger dots (either 21 or 32 microns) that are more suitable for printing.
This optimises the printability and stability in highlight 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