Other Lighting Sources - II - CRI

When looking at alternative ligthing, the notion of the Color Rendering
Index (CRI) also comes into play. It is a measure of how well the light
source outputs all the colors of objects that are lit by that source.

The CRI of an incandescent bulb is nearly 100. Not because it is so
"good" but because it emits light in all the wavelengths that we
perceive. However, the curve is not quite "natural" and so it doesn't
score 100.

Because fluorescent lights are "spikey", they end up with a low CRI of
65 (or so) for cool white and up to 80 - 90 for tri-phosphor
fluorescent. [note the objection to use of the CRI wrt to fluorescents
in the article linked below].

The fact that a light is "warm" or "cool" is not considered in the
index. So you have to look at light temperature (color) as well as the
CRI to get an idea for the quality of the light.

On the left: incandescent. On the right: fluorescent:
http://upload.wikimedia.org/wikipedia/en/0/09/SPD.png

The more technical minded can peruse:
http://en.wikipedia.org/wiki/Color_rendering_index

In summary, consider:
-light color temperature
-Color Rendering Index
when looking at artificial light sources for photography.

Cheers,
Alan
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