Key summary issues
The choice of image input device is determined by the type of print product, characteristics of the used graphic originals and printing technology.
There are scanning systems that use mechanical movement on both or one of the coordinates, as well as electronic, without such movements.
The resolution of scanning the original is directly related to the scale and the screen ruling of the print.
Reduction of the scan spot in relation to the image sampling step is fraught with noise in the received signal, while excessive overlapping of this step by the spot leads to the image defocusing.
The volume of the signal to be processed grows quadratically with the increase in the print dimensions and its screen ruling.
By the type of spectral sensitivity of color channels scanners and digital cameras are mostly densitometers, not colorimeters.
Obtaining intermediate and final copies is characterized by many features that are differently combined in a wide variety of technologies used.
Electro-mechanical engraving is effective in the cylinders preparation for gravure printing.
For the manufacturing of various types of copies, the broad number of impacts on different substrates is used.
Digital printing has a number of fundamental advantages, but at the same time, it does not cover all the possibilities of traditional one.
Parameters of films and plates recorders are largely determined by the scheme of their scanning system.
Halftone transparency - one of the intermediate representations of the required ink coverage, and therefore its properties should provide a non-ambiguous transition of this value on the plate.
The threshold copying density (Dthr) is limited due to the threat of small dots loss due to lateral light scattering in the plate sensitive layer.
Summing up the exposure distributions of adjacent lines in recording on sensitive surface leads to some increase of the dot size and gaps decrease.
Tests
5.1 The dichroic mirror performs the following function:
a) selectively absorbs the incident light, reflecting the rest of it;
b) divides the incident light spectra into two parts;
c) passes the entire unabsorbed part of the incident light.
5.2 The color separation function is not performed by an optical element such as:
a) dichroic mirror;
b) beam-splitting mirror;
c) prism;
d) diffraction grating;
e) coloured glass.
5.3 The light source of the reproduction system is not characterized by such a parameter as:
a) light output;
b) spectral characteristic;
c) dark current;
d) monochromaticity;
e) coherence.
5.4 Among the requirements for the photoelectric transducer (PET) there is no requirement of:
a) spectral sensitivity;
b) integral sensitivity;
c) noise level;
d) light output;
e) power consumption.
5.5 The light sources for image capturing with the color separation do not apply:
a) laser;
b) LED;
c) CRT;
d) incandescent lamp;
d) gas-discharge tube.
5.6 The photoelectric transducer (PET) of the scanning device is not:
a) CCD array;
b) photodiode;
c) PMT;
d) LED array.
5.7The widest range of the light sensitivity has:
a) PMT;
b) CCD;
c) photoresistor;
d) digital camera.
5.8 The technical characteristic of the scanner is not:
a) resolution;
b) screen ruling;
c) ADC bit depth;
d) the number of optical channels.
5.9 The choice of scan spot size for the image input is based on the:
a) resolution of the output device;
b) screen ruling of the print;
c) available scanner resolution;
d) scanner ADC bit depth.
5.10 Taking into account the screen ruling (L) and reproduction scale (M), the scan lines density of the image input is set as:
a) LM;
b) L/M;
c) 2LM;
d) 2/(LM);
e) 1/(2LM).
5.11 Non-uniform sensitivity of the CCD array elements in the flatbed scanner is compensated by:
a) inverted signal of "white";
b) adjustment of the copy illumination;
c) filter of variable density.
5.12 The sampling area greater of theoretical is used for:
a) tone rendition improvement;
b) object moiré suppression;
c) increase of definition;
d) image sharpening.
5.13 The use of the image sampling area much less of theoretical leads to:
a) smooth tone rendering;
b) noise;
c) distortion of contour geometry;
d) increase of contrast.
5.14 The signal value at the photo sensor output is closer to the following parameter of a scanned original:
a) optical density;
b) saturation;
c) reflection;
d) lightness.
5.15 The principal advantage of the computer-to-print technology compared to the traditional is the ability to:
a) quality improvements;
b) personalization;
c) speed increase;
d) reducing the prints cost.
5.16 The smallest dimensional matching of the color separations is provided by the output devices of the type:
a) capstan;
b) in-drum;
c) on-drum.
5.17 The least convenient in terms of automation the exposed material installation and removal are output devices of the type:
a) capstan;
b) in-drum;
c) on-drum.
5.18 Multibeam (parallel) lines recording is used in the on-drum scanners:
a) enhancing the resolution;
b) reducing the drum rotation speed;
c) increasing the accuracy of the lines laying.
5.19 The exposure value in the copying on a litho plate is set according to:
a) recommended optical density (patch number) of the reference grayscale;
b) dot density of the copied transparency;
c) fog+base density of the transparency;
d) achieving the maximum resolution on the plate;
e) density of solid on the transparency.
5.20 The stability of the dot area transfer onto the plate is most accurately characterized by one of the following properties of transparency:
a) density gradient at the copying level;
b) difference between the densities of dot and blank area;
c) dot fringe width.
1 In the visually perceived world this range is 9 to 10 orders of magnitude. Accordingly, due to the mechanism of brightness adaptation, the vision sensitivity changes millions of times.
2 .Its correction in the subsequent stages of the mechanicals, plates and prints manufacture indicates only the lack of rigorous normalization or irrational organization of the whole process.
3 Based on the consumer’s habit to have the possibility of “last moment” manual correction, some scanner vendors intentionally equipped their first EDGs with the patented means of dot edges defocusing.
4 The interaction of such distributions with each other, when touching neighboring dots is considered in the eighth chapter in relation to the TVI effect on the tone rendition.