RE: Colorimeter vs. Spectro
RE: Colorimeter vs. Spectro
- Subject: RE: Colorimeter vs. Spectro
- From: Armand Rosenberg <email@hidden>
- Date: Mon, 3 Jan 2005 15:36:28 -0500
Pardon my outsider's viewpoint in what is clearly a specialized
engineering definition, but isn't a colorimeter basically an
extremely low resolution spectrometer? Instead of the 1-10 nm bands a
prosumer spectrometer (like the Eye-One) might have, a colorimeter
has perhaps 100-150 nm wide bands (or wider), doesn't it? In either
case, however, nothing "falls between the gaps" because there are no
gaps in any such instruments. It's merely a question of resolution. A
"spike" (narrow emission line, perhaps?) can fall on the edge between
two resolution elements of a spectrometer, but it can't fall
"between" them because no spectrometer that I am aware of has an
"in-between" or a "gap." Such very rare circumstances (spikes falling
on edges) can pose difficulties in interpreting the spectra, but only
when resolving those spikes spectrally is critically important -- and
I doubt that's the case in determining color. Work-arounds are
readily available in these rare circumstances to the intelligent
designer of a color system -- it's a matter of intelligently using
the available hardware, not necessarily upgrading it.
True, the broad filters in a colorimeter could have significant
overlap by design or accident -- however, a clever engineer can
simulate this overlap with any higher resolution spectrometer -- and
come to think of it, you don't have to be particularly clever to do
that. The real question is whether the overlap is actually useful to
a color scientist. Does the spectral overlap, for example, emulate
the color response of the human eye? If so, then it's easy to
simulate such an overlap in any measurement with a higher resolution
spectrometer. You just process the available spectral data
appropriately.
As for high-resolution measurements, measuring spectra with sub-nm
accuracy (way-sub-nm!) is really not a big problem with a commercial
scientific instrument, but such an instrument, although readily
available, could cost in the 5- or 6- figures (USD) and require some
technical background to use (ie, it would have no user-friendly
interface for the average consumer). Do you need 0.001 nm resolution
to define color? You could have it of course, but I doubt that you
need it, no matter how sharp the spikes in your phosphors. This is
where the color scientists and the color software designers have to
step in and make intelligent use of the available instruments and
data. I can easily get you a spectrum with pretty much any resolution
(and with no "gaps"), but how you interpret that spectrum in terms of
color, that's the tough part: the "value added" part, if you will.
Who came up with that gap concept? A clever (or not so clever)
marketing guy? Missing data that falls in the gaps? Come on, there
may be some secret sauce in working with color, but measuring spectra
has been done accurately for hundreds of years by physicists (and
more recently, engineers), and with surprisingly high resolution from
very early days. It's the interpretation of the spectra that's tricky
sometimes, not the measurement itself.
I may not be able to tell you immediately what color corresponds to a
given spectrum without some help, but I can tell you how to measure
that spectrum. In this case, color is the interpretation.
Armand
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