Wednesday, 17 October 2012

Design for Print Seminar//colour processes

CMYK Process:
refers to the four inks used in colour printing (cyan, magenta, yellow, key)



The CMYK colour model (process colour, four colour) is a subtractive color model, used in colour printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some colour printing: cyanmagenta,yellow, and key (black). Though it varies by print house, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.
The "K" in CMYK stands for key since in four-colour printing cyan, magenta, and yellow printing plates are carefully keyed or aligned with the key of the black key plate. Some sources suggest that the "K" in CMYK comes from the last letter in "black" and was chosen because B already means blue. However, this explanation, although useful as a mnemonic, is incorrect.
The CMYK model works by partially or entirely masking colours on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks "subtract"brightness from white.
In additive colour models such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural colour of the paper or other background, while black results from a full combination of coloured inks. To save money on ink, and to produce deeper black tones, unsaturated and dark colours are produced by using black ink instead of the combination of cyan, magenta and yellow.


RGB:


The RGB colour model is an additive colour model in which redgreen, and blue light are added together in various ways to reproduce a broad array of colours. The name of the model comes from the initials of the three additive primary colours, red, green, and blue.
The main purpose of the RGB colour model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. Before the electronic age, the RGB colour model already had a solid theory behind it, based in human perception of colours.
RGB is a device-dependent colour model: different devices detect or reproduce a given RGB value differently, since the colour elements (such as phosphors or dyes) and their response to the individual R, G, and B levels vary from manufacturer to manufacturer, or even in the same device over time. Thus an RGB value does not define the same colour across devices without some kind of colour management.
Typical RGB input devices are colour TV and video camerasimage scanners, and digital cameras. Typical RGB output devices are TV sets of various technologies (CRTLCDplasma, etc.), computer and mobile phone displays, video projectors, multicolour LED displays, and large screens such as JumboTron, etc. Colour printers, on the other hand, are not RGB devices, but subtractive colour devices (typically CMYK colour model).
This article discusses concepts common to all the different color spaces that use the RGB colour model, which are used in one implementation or another in colour image-producing technology.


Spot Colour:
in offset printing, a spot colour is any colour generated by an ink (pure of mixed) that is printed using a single run
spot colour can also refer to any colour generated by a non-standard offset ink such as metallic, fluorescent, spot varnish or custom hand-made inks

Generally the cost and potential for problems for a print job increase as one adds more spot colors, due to the increased cost and complexity of added process inks and films, and requiring more runs per finished print. However, because of the complicated process, spot colours are effective at preventing forgeries of moneypassports, bonds and other important documents. 

Duotone:
the halftone reproduction of an image using the superimposition of one contrasting colour halftone over another colour halftone
used to bring out middle tones and highlights of an image
tritones and quadtones can also be created 


Monochrome:
print in one colour or shades of one colour
A monochromatic object or image has colours in shades of limited colors or hues. Images using only shades of grey (with or without black and/or white) are called grayscale or black-and-white. However, scientifically speaking, "Monochromatic light" refers to light of a narrow frequency.

Tints and Shades:
a tint is the mixture of a colour with white- increases lightness
a shade is the mixture of a colour with black- reduces lightness

Pantone:
coding system for different ink colours 
when a printer uses Pantone colours, he buys that specific ink and loads it into his press

the PANTONE MATCHING SYSTEM®:
always show your true colors
The accuracy of colour is critical in design. Because what you see on your monitor is never what will appear on a printed sheet, designers need a standardized color key.
It can be very frustrating to see the logo you worked hard to create look deep blue on the client's letterhead, blue-greenish on his business card, and light blue on his very expensive envelopes.
A way to prevent this is by using a standardized color matching system, such as the PANTONE MATCHING SYSTEM. Though PANTONE is not the only color standardization system, it is the most widely used and the one that most printers understand. Aside from being able to have consistency, PANTONE Colors allow you to use colors that cannot be mixed in CMYK.

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