What are the basic structures of spectral pigment colour theory and how does this apply to print and screen design? (what is RGB and CMYK)
RGB:
http://www.novaprinting.ca/images/RGB.gif
The RGB colour model is based on the theory that all visible colours can be created using the primary additive colours red, green and blue. These colours are known as primary additives because when combined in equal amounts they produce white. When two or three of them are combined in different amounts, other colours are produced. For example, combining red and green in equal amounts creates yellow, green and blue creates cyan, and red and blue creates magenta.
The RGB model is so important to graphic design because it is used in computer monitors. The screen you are reading this very article on is using additive colors to display images and text. Therefore, when designing websites (and other on-screen projects such as presentations), the RGB model is used because the final product is viewed on a computer display.
http://graphicdesign.about.com/od/colorbasics/a/rgb.htm
http://www.colormatters.com/color-and-design/color-systems-rgb-and-cmyk
RGB is a device-dependent color model: different devices detect or reproduce a given RGB value differently, since the color 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 color management.
Typical RGB input devices are colour TV and video cameras, image scanners, and digital cameras. Typical RGB output devices are TV sets of various technologies (CRT, LCD, plasma, etc.), computer and mobile phonedisplays, video projectors, multicolor LED displays, and large screens as JumboTron, etc. Colour printers, on the other hand, are not RGB devices, but subtractive colour devices (typically CMYK colour model).
https://www.princeton.edu/~achaney/tmve/wiki100k/docs/RGB_color_model.html
http://whatis.techtarget.com/definition/RGB-red-green-and-blue
RGB is based on white light, white light is made up of a wide variety of colours:
http://images.tutorvista.com/cms/images/38/dispersion-of-white-light.gif
Although light can appear white, it is actually made up of lots of different colours all added together. The amount of each colour is called the spectrum of the light.
You can see all the different colours using a prism like the one in the picture, which uses refraction (the bending of light) to split the light up. This works because different colours are bent by different amounts and so they come out of the prism in slightly different directions.
http://www.schoolsobservatory.org.uk/astro/stars/spectrum
A prism works through refraction, so what is it?
When light passes from one medium (material) to another it changes speed. This is because the speed of a wave is determined by the medium through which it is passing.
When light speeds up as it passes from one material to another, the angle of refraction is bigger than the angle of incidence.
For example, this happens when light passes from water to air or from glass to water.
http://www.bbc.co.uk/bitesize/higher/physics/radiation/refraction/revision/1/
CMYK:
http://www.novaprinting.ca/images/CMYK.jpg
CMYK is a scheme for combining primary pigments. The C stands for cyan (aqua), M stands for magenta (pink), Y for yellow, and K for Key. The key color in today's printing world is black but it has not always been. During the early days of printing, the colors used for Key have been brown, blue, or black -- whichever was the cheapest ink to acquire at any given time.
The CMYK pigment model works like an "upside-down"version of the RGB (red, green, and blue) color model. Many paint and draw programs can make use of either the RGB or the CMYK model. The RGB scheme is used mainly for computer displays, while the CMYK model is used for printed color illustrations (hard copy).
Pigments, as opposed to colors, represent energy that is not absorbed by a substance such as ink or paint. The primary pigments are cyan (C), magenta (M), and yellow (Y). Sometimes black (K) is also considered a primary pigment, although black can be obtained by combining pure cyan, magenta, and yellow in equal and large amounts.
http://whatis.techtarget.com/definition/CMYK-cyan-magenta-yellow-key
When two RGB colours are mixed equally they produce the colors of the CMYK model, known as subtractive primaries. Green and blue creates cyan (C), red and blue creates magenta (M), and red and green creates yellow (Y). Black is added to the model because it cannot be created with the 3 subtractive primaries (when combined they create a dark brown). The K, or “key,” stands for black.
CMYK in the Printing Process: The four-colour printing process uses four printing plates; one for cyan, one for magenta, one for yellow and one for black. When the colours are combined on paper (they are actually printed as small dots), the human eye sees the final image.
CMYK in Graphic Design: Graphic designers have to deal with the issue of seeing their work on screen in RGB, although their final printed piece will be in CMYK. Digital files should be converted to CMYK before sending to printers, unless otherwise specified.
Because of this issue, it is important to use “swatches” when designing if exact colour matching is important. Swatches provide a designer and client with a printed example of what a colour will look like on paper. A selected swatch colour can then be chosen in Photoshop (or a similar program) to insure the desired results. Even though the on-screen colour won’t exactly match the swatch, you know what your final colour will look like. You can also get a “proof” from a printer, which is an example of your printed piece provided before the entire job is run.
http://graphicdesign.about.com/od/colorbasics/a/cmyk.htm
http://www.catspitproductionsllc.com/Documents/Color%20Wheel%20Finished%20Website.jpg
http://www.colormatters.com/color-and-design/color-systems-rgb-and-cmyk
This means that on the whole RGB colour is made up of light and therefore there are vast amounts of colours. However CMYK is incredibly limited because it is formed through a set amount of inks- therefore the outcomes will also be limited.
http://fc06.deviantart.net/fs41/f/2009/021/7/5/CMYK___A_Minimal_Wallpaper_by_keylocker.jpg
Gamuts
A colour gamut is a subset of colours, such as those in a specific colour space.
http://www.ephotozine.com/article/understanding-colour-gamut-22681
The term colour gamut refers to the range of colours a device can reproduce, the larger or wider the gamut the more rich saturated colours available. As colour gamuts become smaller it is generally these rich saturated colours that are the first to suffer, a phenomena technically referred to as clipping. This clipping phenomenon is most apparent when converting from RGB to CMYK, with many of the rich saturated colours that were available in RGB no longer being available in CMYK.
Display devices like monitors also have gamuts or ranges of colour they can reproduce. So in order to accurately preview your images you would ideally like your display gamut to be at least as large, if not larger, than your printer’s gamut, otherwise clipping will be occurring in your preview.
http://www.wideformatonline.com/index.php/workshops/colour-management/801-colour-gamut-in-laymans-terms.html
http://myworldofcolour.files.wordpress.com/2010/04/rgb_colour_gamut.jpg
A colour gamut defines a more specific range of colours from the range of colours identifiable by the human eye (i.e., the visible spectrum). While colour imaging devices include a wide range of devices, such as digital cameras, scanners, monitors, and printers, since the range of colours they can reproduce varies, the colour gamut is established to make these differences clear and to reconcile the colours that can be used in common between devices.
http://www.eizo.com/global/library/basics/lcd_monitor_color_gamut/
Since we are talking about LCD monitors in this article, we will be looking at the RGB color gamuts and how various monitors are rated for their color. The problem is that there are a variety of different color gamuts that a screen can be rated by.
sRGB, AdobeRGB, NTSC and CIE 1976
In order to quantify how much color a device can handle, it uses one of the standardized color gamuts that define a particular range of color. The most common of the RGB based color gamuts is sRGB. This is the typical color gamut used for all computer displays, TVs, cameras, video recorders and other consumer electronics. It is one of the oldest and therefore narrowest of the color gamuts that is used in reference for computer and consumer electronics.
http://compreviews.about.com/od/monitors/a/LCDColorGamut.htm
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