Jim Worthey, Lighting and Color Research
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Jim Worthey • Lighting & Color Research • jim@jimworthey.com • 301-977-3551 • 11 Rye Court, Gaithersburg, MD 20878-1901, USA

"Camera Design Using Locus of Unit Monochromats"
James A. Worthey & Michael H. Brill
Color Imaging Conference 14
Scottsdale, Arizona, USA
2006 Nov. 9, 3:00 pm

The format of the meeting called for an "interactive presentation," meaning a poster, and  before that a "spotlight session," featuring a 2-minute talk about each poster. 2 slides were shown, and they are available as a pdf file, CamDesLUM2slides.pdf .

 Photo of Count Osterman-Tolstoy
Lev Nikolaevich Tolstoy (1828–1910)

2-minute Speech As Written and Read by Michael H. Brill:

Tolstoy opened his novel Anna Karenina with the sentence, "Happy families are all alike; every unhappy family is unhappy in its own way." A similar thing can be said about cameras: We could call a camera "happy" if it matches the same colors the human does. That requires the camera to satisfy the Maxwell-Ives criterion---its sensitivity functions must be linear combinations of those for human color vision.

How well a camera satisfies the Maxwell-Ives criterion is captured by the Neugebauer index (in the 1950s), which was advanced again by Berthold Horn at MIT (in the 1970s). But one such number cannot convey all kinds of camera failure, and a camera designer must be able to see the kind of failure as a basis for possible improvements. To paraphrase Tolstoy, "Happy cameras are all alike; every unhappy camera is unhappy in its own way."

We propose here a graphical comparison that reveals any Maxwell-Ives failure---and more. The graphs are based on the Locus of Unit Monochromats (or LUM)---the three-dimensional curve traced out in any color space (human or camera) by the unit-power monochromatic lights. You can see here how the LUM captures all the information in the color-matching functions, shown here in an orthonormal basis. Jim Worthey presented these ideas at CIC12.


Our idea in this poster is to compare the human's LUM with the camera's. The camera sensors are orthonormalized in a way that aligns the two LUMs. We show five worked examples. Two cameras show poor wavelength discrimination in a part of the spectrum.  Another LUM shows better wavelength discrimination, but has other problems---some of which are solved by a filter over the camera. LUM pictures may also give insight when a design departs from Maxwell-Ives, but pleases the customer. You may gain new insights from our LUM pictures. Come visit us and try your hand at camera design using LUMs.


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Copyright © 2006 James A. Worthey, email: jim@jimworthey.com
Page last modified, 2006 November 14, 15:47