| Applications: Light Quality
Light Quality: Color Rendering Index: This is how the color of an object under a light fixture is perceived by the eye. Not all lamps will produce the same type of light. The CRI represents the ability of a lamp to render color accurately and to show color shade variations more clearly. High color rendition allows us to see objects, as we would expect them to appear under natural sunlight.
Below is an index of CRI which indicates which lamp will be the most natural-looking and have the least amount of color shift. It is rated on a scale of 0-100 with 100 being the best or most ‘natural, i.e. not too harsh and not too soft:
| QUALITY |
CRI |
| Excellent |
75 - 100 |
| Good |
65 - 75 |
| Fair |
55 - 65 |
| Poor |
0 - 55 |
Color Temperature: A light bulb looks like a certain color because of the Color Temperature. It is not actually how hot the light is, but how the ‘radiator’ reaches a certain temperature to produce the color of the bulb. The ‘radiator’ will change color as the temperature increases from red to orange to yellow, white, blue-white and finally blue. A lamp with a low color temperature will have a "warm" appearance (red, orange, or yellow). Conversely, a lamp with a high color temperature will have a "cool" appearance (blue or blue-white). The scale goes from 1600 Kelvin (e.g. sunset red) to 20,000 Kelvin (deep blue clear sky).
Light Output: Since lamps (bulbs) are standardized, most fixtures will put out a given amount of light per lamp (e.g. 5000 lumens) times the number of lamps (e.g. 4) yielding a total of 20,000 lumens at the fixture. This doesn’t mean there will be 20,000 lumens at working height. The quality, design and cost of the fixture will determine how much light reaches the work surface.
You can have too much light as well as too little. If fixtures designed for high ceilings (e.g. >16 feet) are used for lower ceilings, the light can be painfully glaring. Similarly, the “color temperature” of the light can be less or more light natural light and therefore kinder to the eyes. A good lighting design will incorporate correct light output and color temperature with optimum positioning for the task(s) at hand.
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