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"RGB" Tag


Maxwells Colour System


Sunday, February 11, 2018

The scientist James Clerck Maxwell discovered the additive colour system and showed the first colour photography. He lived in the 19 Century influenced by the Works of Isaac Newton and Thomas Young. He has impact on our knowledge of the Saturn Rings, Electromagnetic waves and the RGB colours.

Maxwell Photography

In his student years at the Cambridge he was fascinated by the questions:

What are colours? Why do we perceive colour? And why are we so coloured?

At that time he read the studies of Thomas Young. Young thought that painters have a much better understanding of colours then scientist had at that time. They used the primary colours to get the full colour spectrum of a painting. He found that there’s a significance of these three primary colours and that Biology has a role to play. He assumed there are three receptors for each of the primary colours in the human brain. By mixing these we receive our full colour view.

Maxwell read about this theory and wanted to prove it by mathematics. He developed a tool to trick the human brain. By spinning the right amounts of red, green and blue on a wheel, it seems like the colours are melting together to white. With this experiment he could prove that what we perceive as white is actually a mix of colours. And that there’s a difference of mixing colours in light and colours in pigments.

Colour Pyramid

From this he developed a Red, Green and Blue colour pyramid. On each corner there is the absolute of one of the primary colours. Towards the middle you get different hues of the colour and the center is white. The Pyramid is built on a x/y Axe. Mapping out a point on the pyramid gives a value of each of the primary colours.

To display his founds, he was invited to give a lecture on colour vision. What he did was to screen the same photograph with a red then green and blue light on top of each other. Where the colours intersect, there is white.

Maxwell Colour Experiment

At this time there was only black and white photography. With this experiment he made the world’s first colour photography. The additive colour system can be understood as the foundation of RGB colours and is used in the screens of most electronic devices today.

RGB


Thursday, February 8, 2018

RGB is an additive colour model, meaning that lights are added together in different frequencies to create colours. For example, when red and green lights are added together they create a yellow colour. This is different to a subtractive colour model where colours are created by mixing dyes, pigment paints etc. which then absorb parts of the full spectrum of colour frequencies available in white light and reflect other frequencies which then give the surface it’s colour.

 

additive-vs-subractive1x

 

 

RGB is used in digital colour sensors and digital colour displays and projectors. Each pixel on a screen has three tiny light sources, red, green and blue in colour. These emit different brightnesses which in the combined effect create the specified colour of the pixel. The sum of all the pixels on the screen will create an image.

 

LCD_RGB

 

These three colours, Red, Green and Blue, are chosen because they correspond to the way the human eye sees colour. We have photoreceptor cells in our eyes called rods and there are three types of rods. One which detects long-wave frequencies of light, another for middle-wave and another for short-wave. Specifically, these correspond to the frequencies of blue, green and red.

 

eye

bubou


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