This circumstance had widely initiated the development of a new industry standards and renewing of the existing ones for objective, quantitative defining the technologic regimes and parameters.
ISO 12647 standard “Graphic technology - Process control for manufacture of half-tone colour separations, proofs and productions prints” was adopted in1996 in Part 1 concerned of “Parameters and measurement methods”. Its other parts recommending the particular values conformably to various kinds of printing were later on re-edited by ISO Technical Committee “Graphic Technology” (TC 130) and, being translated on some other languages, had adapted for the state standards in several countries [2.8, 2.9].
Such standards comprise the general means of professional communication within a print-publishing environment and provide the proper conformity of particular technology stages. Nevertheless, the complete following to standard values guarantees the achievement of some averaged results but not the extremely possible ones for given production conditions. It’s partly explained by these values being empirically got from the industry experience and for some exemplary cases. So, by the great part they haven’t the definite theoretical background in philosophy of finding the optimal meanings. There are no, for example, methodology for choice of such important parameters as the screen ruling, dot form, press settings, etc. So, this kind of issues is especially accentuated in disclosure of the following chapters.
Key summary issues
Image processing can be concerned in such principally different directions as pattern recognition, computer graphics and picture transfer.
The distinctive signs of these directions are: presence or absence of an image at input or output; volume of a source and resulting data and others.
Basic direction in prepress processing is the reproduction of an original presented electronically or on a material substrate.
The goal of reproduction is in producing some intermediate image in digital form, on a film or a plate with its properties providing the best print quality in a press run.
Color of a visual object is essentially and differently changed by the various photographic and electronic means in its initial presentation including such as the graphic original.
Instead of relation to a visually appeared object of surround world the reproduction task would be technically more convenient discerned being referred to its replica – graphic original in electronic or material form.
Complete reproduction system is inherent in three basic functions (stages):
capturing (analysis) with producing the image signal;
signal functional transforms;
making the copy (synthesis).
In relation to a source scene or object the printing comprises just a part of some hybrid system integrating the several complete ones.
Image signal functional transforms can be conditionally subdivided with taking into account their effecting on such copy properties as:
gradation and color;
definition, sharpness, geometric accuracy of fine details and contours;
geometry and size;
image structure.
Quantitative image property parameters are preferred for the objective judgment of its quality.
Individual element is characterized by brightness, lightness, hue, reflection, optical density…while the whole image by contrast, density range, definition, sharpness, tonal content…
Each of an image parameters is respondent by the certain characteristic of reproduction system – second order parameter.
Print quality control is effective in prepress at the condition of further technology stages optimization (by these stages own criteria), normalization and stability.
Tests
2.1 Bringing the data of an original to the volume accommodated by print is provided at:
a) reproduction stage;
b) proof printing;
c) plate making;
d) press make ready;
e) press run.
2.2 Data volume of a halftone print is in the greater degree limited due to:
a) original image;
b) scanning system;
c) signal storage;
d) screening;
e) plate and press resolutions.
2.3 Low spatial frequency transforms have minimal effect on the image:
a) tonal content;
b) color;
c) sharpness and definition;
d) tonal continuity.
2.4 High spatial frequency transforms have minimal effect on the:
a) fine detail and counter geometry;
b) tone rendition;
c) sharpness;
d) definition.
2.5 The group of format transforms doesn’t include the image:
a) magnification;
b) rotation;
c) cropping;
d) color separating;
e) trapping.
2.6 Perception of the light intensity from a viewed print is more directly related to:
a) optical density;
b) brightness;
c) lightness;
d) reflection;
e) contrast.
2.7 Adjacent patches of the visually uniform tonal step wedge differ from each other by an equal discrete of:
a) absorbance;
b) reflection;
c) brightness;
d) lightness;
e) optical density.
2.8 Optical density comprises the logarithm of:
a) absorbance;
b) opacity;
c) reflection;
d) transmittance.
2.9 Optical density comprises 2 units if the reflected (transmitted) part of illumination is equal:
а) 1/2;
b) 1/10;
c) 1/20;
d) 1/50;
e) 1/100.
2.10 Image contrast is estimated as the ratio of:
a) incident and reflected luminous floods;
b) maximal and minimal reflections;
c) maximal and minimal optical densities:
d) color difference - delta E.
2.11Visually percept image contrast is in greater degree defined by the image:
a) brightness range;
b) sharpness;
c) tonal content;
d) definition;
e) average brightness.
2.12 Halftone print definition is estimated by:
a) image data volume;
b) number of picture elements;
c) number of lines discerned at it unit length;
d) printer resolution.
2.13 Image sharpness is directly defined by;
a) minimal width of a reproduced line;
b) inverse value of an edge fringe width;
c) light scattering function;
d) modulation transfer function.
2.14 Transient response characteristic of a reproduction system influences the following image property:
a) definition;
b) sharpness;
c) tonal content;
d) contrast.
2.15 Bit depth of encoding influences on:
a) definition;
b) sharpness;
c) density range;
c) tone rendition smoothness.
2.16 The following attribute isn’t considered as the image parameter:
a) definition;
b) sharpness;
c) resolution;
d) contrast.