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Wednesday, 20 May 2020

Understanding of Colour and Colour models

There are a number of color  models but I am only going to cover 2 here as they are the most often used. 

RGB

This color model is primarily used to describe light. It is used mainly in cameras and scanners. It has 3 color elements that when added together at 100% represent white or pure light. The 3 different colors are Red, Green and Blue. The color model is almost infinite in its range and this in itself is ok until printing is required and that printing is being done through the CMYK color model. The model uses 3 values with each being in a range between 0 and 255 as in the Windows and applications such as Photoshop or as a decimal number up to a maximum of 1 in PDF for example. 

RGB is an additive color model. Adding all of the colors in equal amounts will result in white.

RGB Colour merge
In the web world RGB colours are represented by hex number combinations (the numbering system is ). So for example Red would be #FF0000, Green would be #00FF00 and Blue would be #0000FF. Black is #000000 and White is #FFFFFF. 

CMYK

Cyan/Magenta/Yellow/Knockout used primarily in printing.

The colors are created by printing the colors on top of each other to achieve the required shades. There may may overlaps required on the edges (trapping) to ensure that spaces are not seen as different paper types can expand and shrink when the ink/toner is applied. The color model is much more limited in its range than RGB and therefore care needs to be taken when converting from RGB to CMYK. This can be achieved through color management systems, adding additional colors to the printing run (such as Hexachrome) or using Spot colors that are usually already mixed colors such as Pantone. Printing is effected bu the resolution of the input and output and the paper stock that is being used to print onto both in the surface quality and base color of the media type and also the attributes of the inks being used. Additionally output effects and colors can be modified and enhanced through varnishes such as UV and foils to provide metallic effects.

The model uses 4 values each as a percentage of the 

CMYK is a subtractive color model. Adding all of the colors in equal amounts results in black. However in CMYK this will more than likely result in a dirty color and so with the addition of the K in CMYK the printers also have a real black in order to print a true black.

CMYK Colour merge

This is a simple look at color and I will expand on this in a future blog.

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Michael Peters

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