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Garth,
Cool. The Just Normlicht spectrum does look quite similar to the Lumichrome's, but a bit better (smoother). Could it be that the spectrums are just a bit out of focus? If you used autofocus and focused on the diffraction grating edge, the image would be slightly out of focus, since these are kind of virtual images that exist somewhat behind the actual grating. I manual focused on the images as best I could.
Interesting comparison to the Philips. The Philips is much less smooth, that is, a lot of black gaps. It would be a fairer comparison however if you only had one Philips light on. Maybe we shouldn't have done this, but our ballast is for two lights, and my husband just rotated one light off briefly while I took the Lumichrome pictures.
In any case, these images don't do justice to the spectrum in reality, as the blue-purples, turquoise, yellows and deepest reds are missing. I think we have the same camera Garth, the D100? It is disturbing the camera can't capture these colors, but not completely surprising. The camera separates the light through red, green and blue filters before reaching the CCD. Maybe someday the technology will change and the digital filter system will be redone and based on the Munsell system? I'm not sure how these images would look if taken on a film-based camera?
For comparison's sake, I took a picture of the spectrum of northeast light (not that is really matters the direction of light) seen through a pinhole. The pinhole was just a piece of cardboard with a hole from a hole punch. You can see the smoothness of the gradient in the image below, but once again, in reality the image is a smooth (and perfect) rainbow of colors. At least this allows a benchmark comparison of the artificial lights against northlight, seen through the skewed eyes of a camera. Below is also a picture of the setup, with the pinhole in the cardboard surrounded by several pieces of dark cloth held in place with clothespins, so no light will interfere with the image. The grating was 5'4" from the point source of light and the camera ~9' from the light source.
The other artificial light images probably should have been taken using this point source method, as you can see the gradient better. Maybe I'll redo all of them, and place them side by side along with the northlight picture for comparison's sake.
Holly
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