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Light Theory

 

Light quality - CRI (color rendering index)

The quality of white light is described of a CRI value between 0 and 100. The most optimal value is a CRI of 100, equal to that of sunlight. A high CRI value means that the white light is compsed of many colors, whereas a low CRI of 20 means that the light consists of very few colors, or that the light quality and color reproduction is very poor.  Good color rendering are CRI values between 70 and 100.

 

Color Temperature - CCT

This value says something about how light is perceived by the eye. For example, a high value of 10 000K will be perceived as blue white, whereas a low value of 2000K will be picked up as yellow/red. This value does not say anything about the quality of light, but about color perception.

Good light quality is a composite of all the colors in the rainbow. Therefore, to create white light with only 3 colors is possible, but will not give good light quality. See below for light from the four different color temperatures.

                    
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Light intensity (Candela)

This value describes how strong the light is in a certain direction. Normally, a floodlight's candela value is given by where it points. In order to provide full illumination of a deck from long distance (top of wheelhouse) a high candela value is required. For fixtures placed on deck it is better with a large scattering angle and a high lumen value.

 

Total light output (Lumen)

The total amount of light emitted from a light source. A high lumen value does not say anything about how much light there will be in the desired area, thus, to compare products only on lumen values can be very misleading.

 

Light amount in an area (Lux)

The amount of light which is located in a particular area is expressed in Lux. For example, if measured on the deck of a vessel it will describe how much light there is in the position of measurement.