Exposure (pressure)

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When exposure is called a process in the pre-press, to produce a tangible image structure from the control data after rasterization.

Imagesetter

There are different imagesetters:

1. Film imagesetter (computer to film)
   1. Internal drum imagesetter
   2. External drum imagesetter
   3. Slide lights
   4. Capstan
2. Digital platesetter (computer to plate)
   1. Internal drum imagesetter
   2. External drum imagesetter
   3. Flatbed imagesetter (instead of capstan)

Working principle

The raster data (pixel matrix) from the raster image process (RIP) are applied line by line and point by point to the film / plate with a laser beam. The individual raster points are composed of several laser spots.

This requires very precise positioning of the laser pulses.

An alternative to laser exposure is the exposure of UV light-sensitive plates with UV light. The light matrix is ​​an important part of this. It consists of LCD elements that can be individually switched to allow light to pass through or to block light. The same technology is also used in TFT displays.

In terms of lighting technology , the exposure H _V ( unit : lux seconds or watt seconds per square meter) is the illuminance E _V that acts on a receiver over a period t:

${\displaystyle H_{V}=E_{V}\cdot t\quad [lxs]{\mbox{ bzw. }}\left[{Ws \over {m^{2}}}\right]}$