Full color system

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In the field of printing technology, a full color system is a printing system based mostly on a laser printer , which generates mixed colors by real color mixing on the printing medium.

technology

Simple color printers, which can only display one color per pixel, expand the print raster so that a grid of usually 8 × 8 print points is available for each pixel to be displayed. These 64 dots are printed with the appropriate printing inks to achieve the desired image color. The resolution is reduced by a factor of 8 with this method, for example an actual resolution of 300 dpi is achieved with a physical resolution of 2400 dpi . This procedure is necessary because each print point can only be printed with a 100 percent color application. All inkjet and conventional laser printers use this raster process.

Full color systems differ in two ways:

  • The color application of a printing point can vary.
  • The four basic colors can be printed on top of each other.

While in normal laser printers the image drum is electrically charged and completely discharged by exposing corresponding pixels on the drum at these points, i.e. a pixel is defined by charging or not charging at the corresponding point on the drum, full-color systems also use partial charges where a lower charge is used Amount of toner remains. The partial charges are achieved by gradually reducing a full charge. Gradual degradation is achieved either by changing the dwell time of the laser or by repeatedly sweeping over the area to be discharged. More modern systems are able to change the brightness of the light elements in a very short time and can therefore cover multiple times or dispense with different dwell times.

In addition, the individual layers of color are printed on top of one another and mix to form a full-tone color when they are fixed. While classic raster printing systems produce color at the expense of resolution, the usable resolution does not change with full-color systems.

In the meantime, some manufacturers also offer conventional laser printers that can influence and graduate the charges within certain limits.

The characteristics of the toner in a full-color system differ from those of a laser printer, since the latter does not have to print several layers on top of one another. Two systems are currently in use: wax and metal oxide toners. In the case of the latter, the final fixation is usually carried out using a fixing oil .

Simple full-color systems work with an image drum and print the medium in four passes. More complex systems work with four drums - one for each of the printing inks - and thus achieve speeds of up to 100 pages per minute.

Advantages and disadvantages

The advantages of full color systems are the very large color spaces , rich colors with a high depth effect and the very good printability of tints with saturation below 20%, which with a normal printer are either already outside the reproducible color space or can be recognized by strong grizzling (e . in bright clouds). Since the systems work without a classic printing screen, they are not familiar with the problem of moiré effects.

The disadvantages are the very high purchase price, the size of the devices and the relatively high maintenance costs. Furthermore, due to the principle, there is a three-dimensional application of paint and a glossy effect on the printed areas, which is not always desirable. The systems are usually not suitable for mass print products.

application

Full color systems reward the user with excellent results, but place very high demands on the data to be printed. The large color space, the high contrast sharpness not only enhance the image impression, but also disturbances such. B. by JPEG fragments and stairs at the edges, if the resolution of the original is too low. At this point, halftone printing processes are “more grateful”. Due to the rasterization of conventional printers, which often acts like a soft focus on pixel images, this effect is completely eliminated in full-color systems. The image sharpness and the color reproduction are higher than that of a monitor, so that some disturbances are only visible on the print.

Areas of application

Full-color systems are considerably more complex to manufacture than conventional laser printing systems and are used, among other things, in print shops and for art prints. These systems are most commonly found in advertising agencies. Since the color space is far above that of conventional printing machines, the devices are used for the proof , since almost all printing machines can be simulated with them. The market shows a clear focus on professional / commercial use, mainly due to the high purchase price (from 10,000 euros for simple DIN A4 devices in the basic configuration) - devices for private use are currently not on the market. Professional duplex A3 devices with integrated RIP start with the usual attachments at around 30,000 euros and quickly reach the 250,000 euros mark for four-drum systems with high throughput.