Design Basics: RGB vs CMYK

Origins of RGB

The RGB color model is based upon the theory of Young Helmhotz of trichromatic color vision, developed by Thomas Young and Hermann von Helmholtz in the early to mid nineteenth century. James Clerk Maxwell elaborated on that theory with the color triangle around 1860. RGB or Red, Green, Blue is an additive model of color in which colors of light in red, green, and blue are added together to form a various array of colors.

What is Additive Color?

The form of RGB is through varying intensity of light added to one another. Zero of each component is the darkest value (black), 255 of each component is the lightest value (white). White point determines the quality of the white displayed. This additive model changes the wavelength to make the final color’s spectrum. Essentially this is the opposite of the subtractive model of CMYK. RGB is mainly used in the digital space to display images on screens such as: televisions, tablets, computers, and smart phones. RGB is also device dependent, in that, it corresponds to the properties of the device it is displayed upon and varies from manufacturer to manufacturer.

What is CMYK?

The CMYK color model (also known as four color process) is a subtractive color model based on the CMY color model. CMYK stands for cyan, magenta, yellow, and key/black. Key is a printing term derived from the use of a key plate, generally black in four color process, which helps align the other color plates. Where RGB in full intensity you attain white, CMY at full intensity gets an imperfect black sometimes called composite black.

What is Subtractive Color?

Where RGB starts at black when all values are at zero, CMYK starts with the white of the paper and as ink or toner is put down it creates a mask by reflecting the light. It is considered subtractive because the inks “subtract” red, green, and blue from white. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow. As mentioned earlier, CMY makes a black like color but it is expensive to print blacks in that way. To get better blacks in those darker areas a “bedding” is first applied of a color or gray in CMY then a full layer of black is added on top, thus creating a rich black.

Design for the End Result

When designing for primary usage on screens, computers, websites, etc. use the RGB color model. Conversely, when designing for printed media you will use the CMYK color model. Also, though some current digital printers will automatically adjust images in the print file to CMYK when they’re in RGB, it’s a best practice to make sure your images are always in the correct color model for the end result. Remember to look to Purple Dog Print Co. when you’re in need of printed media.

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