2.2 Original image and goal of reproduction

Originals for print reproduction differ in:

• type of substrate (transparent, opaque; hard, flexible);

• color (b/w, monochrome, chromatic);

• structure (line work - LW, continuous tone – CT, halftone – secondary);

• kind of their creating (photographs, drawings, paintings, prints);

• form of their presenting (on substrate and electronic, including those of the digital photography).

Reproduction of the latter kind pictorial data omits the stages of electro-optical analysis, color separation and digitizing but in the other relations doesn’t differ of that used for originals initially presented on a substrate. Nevertheless, in spite of being somehow shorter, the problem of adequate digital image file values interpretation is inherent in that kind of a source data processing. As will be shown lower, being picked up from the same visual object these values may essentially vary due to the difference in image capturing conditions, devices, etc. The need exists in defining the image property they present as well as the method, metric and numerical units used in encoding to reveal their factual meaning.

Type of original copy cardinally defines the character of required reproduction process, equipment and materials used therein as well as the staff qualification. From the other hand, it also determines the quality level of a copy could be attained at given printing conditions. There were the attempts to regulate publisher – printer relationships by the development of a standard adjusting the original properties and their possible reproduction parameters.

Images initially produced for another purposes and viewing conditions are also often used as illustrative originals. It can be, for example, the color transparent positive – slide intended for projection in a dark room by the light of a tungsten lamp. Negative films are used for making color pictures on photosensitive paper to be viewed in common indoor lightening environment. Characteristics of television signals and digital photography provide, first of all, the proper display on TV screens and computer monitors.

Color properties of dyes and pigments on images produced by traditional photography as well as with the use of thermo transfer, ink jet, electro photographic digital printers are non-identical too. So, the color presentation of a scene by various kinds of objects – originals is already inherent in certain specific which results in the difference of signals produced at their capturing by the same scanner or digital camera. From the other hand, the signals generated for the same original by different kinds of image inputs aren’t identical too because of non similarity of their characteristics. This creates the problem of the so called signals compatibility by input in the reproduction environment operating with various kinds of originals and multiple image capturing means as was indicated in figure 1.12.

Resulting copy quality interpretation stays problematic too because it’s, as a rule, given in the absence of a source imaged object and mostly estimated by memory, with the use of individual viewing experience, preferences and expectations. Quality level can also be corresponded to the simplified evaluation of a customer or specified examination of an expert [2.3; 2.4].

Such questions are in greater degree related to the creative, editorial stage rather than to reproduction technology itself. So, the goal of the latter is more suitable to be concerned not in relation of a source viewed object or scene but as applied to some of its secondary presentations such as a certain kind of original copy or a signal of digital camera, TV channel, etc.

It’s also useful to see as the congruent part of reproduction technology the issue of signals compatibility by output which is stipulated by the requirement of visual matching an original in all the variety of methods for print copies and proofs production as was designated earlier in figure 1.13.

So, the goal of illustrative printing can be in general defined as the producing of a copy which at the target precision rate matches a certain original or visual object with the reproduction quality estimation by the degree of their corresponding each other. Such purpose motivates, in turn, the need in described lower the quality measurement quantitative parameters to make this estimation objectively realistic.