It is an advantage of open publishing systems that it is possible for the user to put together parts of different suppliers to a complete
system. Standardized interfaces provide the links between the different parts of a system.
One of the key technologies for output is PostScript, the well-known page description language, developed by Adobe systems.
It has become a de-facto standard for computer publishing applications.
The main advantage of PostScript is its device independence: Any document can be printed on any PostScript output device in
any available resolution.
The idea of device independence, however, leads to some problems: If there are problems concerning output quality, it is very
difficult to detect the source of these problems. Without additional help it is often impossible to find out which part of the system
(scanner, software, output engine, the developing process) causes the problem.
Until now, Computer Publishing systems lacked control systems like those used for offset printing.
The objectives of the VFG-GLV-PostScript-targets were to develop test targets, which enable any user to evaluate and maintain
the quality of any output device (printer or imagesetter). These test targets should be supplier independent.
1.3 Developing the test targets
Developing the test targets started early in 1990 at the institute for Graphic arts in Vienna (Graphische Lehr- und Versuchsanstalt,
GLV). The first protoypes were used at CeBIT 1990 for an imagesetter comparison. In 199 1 the concept was refined, giving two
test targets: The VFG-PTF and the VFG-PQF. After field testing in 199 1 they are available around the world since September1991.
The test targets were developed using direct PostScript programming. Main parameters of the output device are interrogated and
are used to build test targets suited for a specific device resolution on the fly. Some test targets are device dependent and show
output quality for a specific device at a specific resolution. This is the advantage of a test target, created by a program. It allows
to deal with specific devices.
The test targets ar therefore suited to test imagesetters at high resolutions as well as low-res laserprinters.
1.4 VFG-PTF: Quality evaluation
The VFG-PTF test target helps evaluate the quality of a PostScript printer or imagesetter. Its size of 20x20 cm allows for a large
quantity oftest targets. The test target checks resolution, screen angles, density, and the quality of mechanical and optical system.
The evalutation of the test targets will be done visually or using a densitometer.
1.5 VFG-PQF: Quality maintenance
The VFG-PQF test target is used for job quality control. It is pasted into a PageMaker-, Ventura Publisher- or XPress-job and will
be sent to the printer with the job. This allows quality control for every page processed