Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] About black zones in screens



Both excellent points. This has been a great question and a great conversation.

Mike

----- Original Message ----- From: "John Clement" <clement@hal-pc.org>
To: "'Forum for Physics Educators'" <phys-l@carnot.physics.buffalo.edu>
Sent: Saturday, November 20, 2010 9:44 PM
Subject: Re: [Phys-l] About black zones in screens


The mixing of color in the textbooks is actually a description of how you
engineer color film, TV... And it doesn't work that way with natural
illumination.

I would say red plus green does make yellow because red, green and yellow
are subjective descriptions, not specifying the wavelength of light. I have
never seen a text that says that red wavelengths plus green wavelengths make
yellow wavelengths. And of course the ends of the spectrum together make
purple which is not even a spectral color.

So I would say the descriptions in terms of color are describing what we
see, and not the actual mixture of wavelengths. In either case because of
color constancy radically different combinations of wavelengths can produce
the same subjective perception. This latter phenomenon is what I think the
texts are negligent in not pointing it out.

I suspect that some high end color printing software may build in an
algorithm for judging how you actually perceive color and alter the mixtures
accordingly. There is some absolutely fantastic software that is able to
generally judge what the actual color was in a photo and adjust it so it
looks correct. It is put out by Applied Science Fiction, a division of
Kodak. Kodak's printing hardware has it built in. You can also get
scanners that build it in. It is not perfect, but it works well at least
90% of the time. They also marketed "Digital Ice" which uses infrared
sensors to detect dirt on negatives. I don't know if they invented it, and
the division was probably a small company bought by Kodak.

John M. Clement
Houston, TX



To address another comment about color mixing, I've written about this
before on the NSTA list, so I won't go into any detail here, but as far
as physics is concerned, there is no such thing as color mixing the way
it is described in textbooks. It's all an illusion caused by the way the
human visual system works.

Red plus Green does not make a new wavelength of light - it only *looks*
yellow.



_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l

__________ Information from ESET Smart Security, version of virus signature database 5635 (20101120) __________

The message was checked by ESET Smart Security.

http://www.eset.com





__________ Information from ESET Smart Security, version of virus signature database 5635 (20101120) __________

The message was checked by ESET Smart Security.

http://www.eset.com