profbowman Loc: Harrisonburg, VA, USA

One example of how colors can look "pure" and thus we expect it to cover a narrow band of wavelengths, but a spectral analysis might show that this observed color is composed of a complex and broad spectrum. For a chemistry experiment I made up solutions of red and yellow food coloring (dyes) diluted in water. Figure 4 shows these two isolated spectra. Then I made a solution of approximately half- red dye and half yellow dye. The color was a nice clear orange color. The spectrum of this orange sample is also shown in Figure 4. Note this spectrum spread over all the wavelengths of the two separate colors and that even the red dye has a low shoulder spread into the yellow wavelengths. So, even simple dyes can be very complex.

profbowman Loc: Harrisonburg, VA, USA

David, I am sure you have had a lot experience with light sources. Now if your "Timbuktu" (some how as kids we used this city in Africa to mean anything that was unknown to us and far away) was not far from my Harrisonburg, VA, USA, we could meet and tell stories. --Richard

carlberg

I marvel how "white" LEDs can can reproduce a scanned color photograph so accurately.

carlberg

We're located in Santa Barbara, California. Unfortunately not an afternoon's drive to Harrisonburg, but maybe some day when the pandemic #%&* is over... And of course the invitation is good on this end as well.

Stay healthy..

David C.

profbowman Loc: Harrisonburg, VA, USA

We want a white light source but then a sensor that has at least three colored sensors (RGB or NIR or RGB-D today or other letters tomorrow). One would actually want a light source that matched the Sun's spectra, but there does not seem to be any unless one can make a cheap and cool-operating incandescent source with a very hot filament. --Richard

carlberg

Richard,

I looked up Harrisonburg on Google maps. Looks like a lovely area.

David C.
carlberg@ix.netcom.com

profbowman Loc: Harrisonburg, VA, USA

We have lived in this area since 1986, and we graduated from college form here: Me (1966-70: Elsie (1967-69). We like John Devers song, "Oh Shenandoah," but he got it slightly wrong. The Shenandoah River and the Blue Ridge Mountains are in western Virginia and not in West Virginia. --Richard