re: Epson 5500 Metamerism
re: Epson 5500 Metamerism
- Subject: re: Epson 5500 Metamerism
- From: Chris Murphy <email@hidden>
- Date: Wed, 29 Aug 2001 17:04:31 -0600
Dan Reid <email@hidden> writes:
>
Tungsten bulbs have a rounded spectral power distribution kind of like a
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bell curve. D50 simulator fluorescent simulator bulbs by their very design
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have problems getting a close *spectral* match to D50. Typically you see a
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large spike in, guess what, yellow/green region and blue/purple.
Unfiltered tungsten bulbs have a fairly straight line spectral power
distribution that increases in output with longer wavelengths, with
approximately eight times the output at 700nm than at 400nm.
Fluorescent lights do have a quite a shockingly spikey spectral power
distribution, with peaks at 397nm (violet-indigo), 432nm (indigo-blue),
548nm (green-yellow), and a smaller one at 577nm. At about 650nm, the
output starts to drop off, thus fluorescent 5000K lighting has quite a
bit less red output than D50.
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Also fluorescent tubes
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don't excite the UV portion similar to D50 or daylight. I found engaging a
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D50 fluorescent tube AND and UV bulb made the perceived color a lot better
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than just D50 fluorescent tubes.
It's very interesting that you get better results by adding UV. I'm not
sure how to reconcile this because D50 is quite low in UV output, and so
are tungsten lights. Fluorescent lights actually have higher amounts of
UV than D50. It's the mercury vapor content inside fluorescent tubes that
is the source of UV output as well as the spikes in the spectral power
distribution.
Chris Murphy
Color Remedies (tm)
Boulder, CO
303-415-9932