Chromagraph DC 300
The Chromagraph DC 300 is a drum scanner that was developed by Rudolf Hell and came onto the market in 1965. It was one of the most successful and well-known professional scanners of its time and has been installed around 2,500 times worldwide. At the end of the 1990s, this scanner technology was replaced by more economical flatbed scanners and digital cameras .
technology
The Chromagraph DC 300 is an electronic daylight scanner that can be used to produce corrected color separations for several printing processes. Suitable templates for scanning are flexible colored reflective images and slides . The enlargement or reduction ratio is between 1685% and 33% and the maximum output format is 40 × 50 cm. The screen ruling can be selected between 34 and 80 screens and the screen angle is 0 ° for yellow, 45 ° for black, −18.4 ° for cyan and + 18.4 ° for magenta. However, the screen angle can be freely selected for all colors.
The reproduction template is fixed on the scanning roller, an acrylic glass tube , with adhesive tape. The scanning unit consists of a halogen light source and four photo multipliers , which are located in the optical head together with the recording optics and the associated electronics. The optical head moves slowly along the rotating cylinder, the photo multipliers receive the light reflected from the original image and pass it on as electrical signals. Three of these signals reflect the proportion of blue, red and green light, the fourth is used for masking the surroundings. The electrical signals are processed in a four-channel computer, which can be specifically programmed for the desired color and tonal value corrections.
The writing signal of the color computer is directed to the halftone or raster recording head via the scale computer. A special device enables the color separations to be rasterized. The raster points are written on the film to be exposed with the help of laser beams . They consist of six digitally modulated sub-points that reach the film via a fiber optic cable. The digital structure of the halftone dots means that they are more sharply defined and therefore less sensitive to fluctuations in the development of the film, for example due to temperature and development time. Nevertheless, the electronically generated raster point can be changed manually afterwards using Farmer's attenuators .
history
In 1958 Hell developed the first drum scanner. The Colorgraph was a monster with 500 tubes in the arithmetic unit. The electronics took an hour to warm up before they could work. Nevertheless, 24 of these systems were sold worldwide. In 1965, Hell introduced the first Chromagraph , a scanner for color-corrected halftone color separations. The Chromagraph was so successful that Hell had sold 100 devices a year later. In the next few years this series was continuously improved. The Combi-Chromagraph 288 was able for the first time to combine images and texts from three scanning cylinders onto a recording roller. In 1969 the Vario-Chromagraph was presented, which could enlarge and rasterize the color separations for the first time using a contact grid.
The Chromagraph DC 300 daylight scanner, developed in 1971, was able to zoom in and out by temporarily storing the scan data and then outputting it either accelerated or delayed depending on the format. In 1973 more than 100 scanners of this type were sold worldwide. In order to eliminate the shortcomings of the contact grid, the electronic grid for the Chromagraph DC 300 ER was developed in the same year . Without the interposition of a contact grid, laser beams hit the film and generated modulated grid points. In 1977 the five hundredth and in 1979 the thousandth Chromagraph DC 300 was installed. In 1981 the Chromagraph DC 350 came onto the market with completely newly developed electronics.
Individual evidence
- ↑ a b c Chromagraph DC 300 , accessed August 28, 2016
- ↑ Rudolf Hell 1960-1973 ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed October 14, 2010
- ↑ Rudolf Hell 1974-1984 ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed October 14, 2015
literature
- Helmut Kipphan (Hrsg.): Handbuch der Printmedien. Springer-Verlag, November 2000. ISBN 3-540-66941-8
- Michael Limburg: The digital Gutenberg. Springer-Verlag, November 1996. ISBN 3-540-61204-1