All color monitors use red, green and blue input signals to create the colors that the operator sees on the screen. If the images are to be printed the values must transfer from RGB to CMYK – the abbreviation for the cyan, magenta, yellow and black values, which are needed for color reproduction by process color printing. The K comes from the traditional printing description of the black separation as the ‘Key’, which is added to enhance color and contrast.
Color separation – When required for multi-color process printing a full colored picture or illustration is normally first divided into four separate subtractive color components by either electronic/ laser scanning or through The use of color f1ltersin a process camera prior to the production of the printing plate. A color image separated in this way will provide films for yellow, cyan, magenta and black (CMYK*) plate production.
Each color on the film is represented as lines of dots set at specific angles which, when overlaid, will combine as layers of dots forming tiny repeat rosette patterns that simulate shades of color when seen at a distance. If an image is required for line printing only, the separated films still represent each of the colors, (which in Some printing processes may be more than four colors), but there is no dot formation or rosette pattern involved.
Spot Color – Brand owners often require a separate specific custom made color – outside of the normal fourcolor process colors – to distinguish their own products from competitive products on retail shelves. Therefore it is not a color separation and called Spot color or special color. The special color ink is much more expensive that normal CMYK ink, therefore if you really use so many special color, you can blend it by yourselves using a special software, such as Gretag Macbeth ink formulation. From all spot color only less than 50% can be match by four color separation.
Hexachrome – As the gamut of color separation is limited, Pantone develop a six-color process developed in order to create a larger gamut of reproducible color. It is claimed that the number of spot colors that can be faithfully reproduced by the Hexachrome process increases from 50% to 90%.
Highlight – The areas of a printed image which are nearest to white. The whitest part of a halftone when printed, represented by the area with the smallest dots or no dots at all. Some scanning and image manipulation programs require the operator to set the ‘white’ and ‘black’ points. Because the small dots of highlight areas in flexo are subject to relatively large dot gain, it is ~ important that any highlight limitations are discussed with the printer before any separations are made. The lowest or smallest highlight and the resolution of the plate/film is the key to determine the anilox rolls must be used (in average for min of 10% the anilox roll must be 3 times the plate, while for 5%.
Densitometer – Densitometers used for the measurement and control of color inks on a substrate are reflection densitometers. They use red, green and blue color filters to measure and control color proofs and sheets printed with special color bars, which consist of small blocks of each color, graded halftone tints and overprints of the colors. Measurements taken are ink strength, dot gain, neutral gray balance and ink trapping on the press.
Color matching – The duplication or exact matching of a given color sample in terms of hue, value and intensity. In ink this is done by blending the appropriate elements of an inks or inks to achieve the color match required. Each color should be verified under correct lighting conditions. When appropriate use color measurement instruments to verify an acceptable match.
Dot gain – A printing characteristic or defect in which the size of a half-tone dot changes as a result of plate making and printing by different printing processes. When dots are transferred from a film to a plate, they will tend to grow in size during light exposure. Ink transferred from the plate to the label substrate will again increase in size. Fluid inks and compressible plates used in the flexographic process also tend to increase dot gain, varying according to press and substrate used. Fortunately, dot gain is largely predictable and consistent, and can therefore be compensated for, especially if you used digital photopolymer plate as the dot gain of each printing machine can be input in the digital file (make it smaller as of to meet the grow in the printing process). As if we print with too big dot gain, the image will look darker (too much ink transfer) just like the image below.
Fingerprinting – The printing of a special test form or test run on a press so as to determine the registration, dot gain, distortion and other characteristics of the press. Once known, these can be compensated for at the design, film or plate making stages. With making the fingerprint, you will know the characteristic each of your printing machine and you can put on the memory on your computer that for each printing unit the right dot gain, distortion, etc. Even though it seem a waste of time and cost at the beginning, but for sure it will safe your production year for the many years after.
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