Caution urged when considering LED light sources for light-sensitive materials

I read with interest the article by Dale Paul Kronkright in
Conservation DistList Instance: 23:38 Sunday, April 4, 2010. LEDs
are preferable for many applications because they convert electrical
energy into photons so efficiently.

Dale reports about colour discrimination within the human visible
spectrum. One must also be aware that many so called white LEDs are
anything but that. Manufacturers employ two tricks to make white
light. One is to use several LEDs that each emit a primary colour.
When combined these colours look white to the human eye. The other
is to cover a blue LED in a phosphorescent chemical, or phosphor,
that absorbs a portion of the emitted bluish light and re-emits it
as amber, so again you see the combination as white. Does this
affect how we view an object?

Ben Hodgetts
Conservator


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                  Conservation DistList Instance 23:39
                   Distributed: Friday, April 9, 2010
                       Message Id: cdl-23-39-009
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