gd talk october 2014 [compatibility mode]

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www.light-designs.co.uk

Without light there is no colour…

What is colour? “No object of itself alone has colour. We know that even the most

brightly coloured object, if taken into total darkness, loses its colour. Therefore, if an object is dependent upon light for colour, colour must be a property of light. And so it is."

Paul Outerbridge, Photographer 1896 - 1958

Steve AllenLighting Design Director

Connect Intelligence Ltd



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www.light-designs.co.uk www.light-designs.co.uk



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What is an LED ?LED semi conductors are crystals comprised of combinations of

typically two or three inorganic elements such as gallium phosphide (GaP) or gallium indium nitride (GalnN).

When an electric field is applied to the material, negatively charged electrons and positively charged

holes (positively charged electron vacancies) are produced and exist at different energy levels

separated by a “band gap”. When these subsequently recombine, the released band-gap energy is converted into a photon of light with a frequency, and hence colour, that is equivalent to the band-gap

energy.

This results in the emission of light in a very narrow spectrum. Because the light is narrow band,SSL

is capable of much higher light-emission efficiencies than are incandescent light sources.



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•Reduce energy costs.

•Negate maintenance for lighting.

•Maintain light quality.

•Fully controllable lighting.

•No disposal cost.

•No dangerous materials.

•Minimal heat.

•No UV/Infrared.

•Made in the UK from recycled materials

Benefits of effective LED



The strength of light

output is expressed in lumens not watts

USE WITH CARE

As this dose not take into account a lot off factors including:

Light distributionLight colour temperature Its ability to render

colour.


MR16 lamps 50 W power

ratings (800 lumens) 50w = 800lm so 16 lm/w 2700k-3100k 95 CRI


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Colour Rendering Index (CRI).


CRI 92


CRI 80


Compare the details of each image, noting where the colours are pretty similar, such as

the red & orange peppers, and the radishes. Then look at the items with colours rendered differently, such as the floor, cutting board, carrots, cabbage, and lettuce leaf, for example. A low colour Rendering Index does not mean all colours will shift, and no 2

lamps with the same low CRI rating will necessarily have the same errors in rendering


A simple definition of colour Rendering Index (CRI) would measure the ability

of a light source to accurately render all frequencies of its colour spectrum when compared to a perfect reference light of a similar type (colour temperature). It is rated on a scale from 1-100. The lower the CRI rating, the

less accurately colours will be reproduced. Light sources that are incandescent radiators have a CRI of 100 since all colours in their spectrum are rendered equally. As stated earlier, light sources that are not

incandescent radiators will have Correlated colour Temperatures.

Typical spectral power

distribution graph for daylight.

3000k spectral power

distribution for a particular fluorescent lamp 80CRI.

5000k spectral power

distribution for a particular fluorescent lamp 98CRI.


Colour Temperature

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It's important to keep in mind that even tho' reddish light has a technically lower colour

temperature, its frequently described as warm. Bluish light, which has a higher colour temperature, is described as cool. In this instance, warmer & cooler describe colour, not temperature.


Colour temperature has been described most simply as a method of describing the

colour characteristics of light, usually either warm (yellowish) or cool (bluish), and measuring it in degrees of Kelvin (°K)

The colour temperature of daylight varies, but is often in the 5000K to 7000K range.

When the desired lighting effect is "warm", use light sources in the 2700K - 2800K range. Most common incandescent light bulbs will produce light in this colour

temperature range.

It is important to note that colour temperature is not the same as colour rendering. The colour temperature of a light source does not describe or predict the ability of that light source to render colour accurately



gd talk october 2014 [compatibility mode]

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