[Tig] D.I and 6500k

Chuck Harrison cfharr
Sat Mar 5 20:21:38 GMT 2005


Hi, all.

Not surprisingly, there has been much research on the spectral
composition of daylight over the centuries.

The CIE Dxx series of "standard daylight" spectra are approximations
based on work in the 1960s which included many hundreds of
measurements at different locations, times of day, times of year,
angular orientations, etc.

There is a good summary in Wyszecki & Stiles sec. 1.2.1.
Judd, MacAdam, and Wyszecki reported the eigenvector analysis
in JOSA 54:1031 (1964), "Spectral Distribution of Typical
Daylight as a Function of Correlated Color Temperature".
Visit your friendly university library for the straight
story.

AFAIK a reference to any single magic location and time of
measurement is just urban legend.

Incidentally, I have been party to discussions within SMPTE
regarding whitepoint specifications for upcoming DCinema
(digital projection) standards.
IMHO the two biggest concerns have been
 (1) compatibility with actual practice in commercial
      motion picture presentation today (which is FAR from
      5400 K -- we are NOT using white-flame carbon arcs
      any more), so that digital and film presentations
      will look very similar in theatrical release
 (2) efficient use of the light from Xenon lamps
SMPTE standards on this topic are still going through the
balloting process.

Peace,
  Chuck





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