Date: Thu Oct 23 09:50:12 2008

Author: Bill Norwood

Subject: Re: [tap-1] Color Mixing

Post:

Hi Taplers, I have been deleting these things without reading them, not
realizing that the topic was color mixing. Hence the suggested subject name
change. Bill

-----Original Message-----
From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Richard Heckathorn
Sent: Wednesday, October 22, 2008 9:51 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] New member of PIRA seeks some advice... (fwd) and

Greetings,

Thanks for additional information.

I agree with all you said.

My original statement was to raise the question
and see what you get.

Nothing to do with red, green, blue color addition
except using the three different colors.

While I am at it, I'm sure you have used slats of
different widths and shine different color light
through it,

Dick


Helping teachers who facilitate, motivating
students who learn.
Dick Heckathorn 14665 Pawnee Trail Middleburg
Hts, OH 44130 440-826-0834
http://web.cvcaroyals.org/~rheckathorn/
Adjunct Physics Teacher - Baldwin Wallace College
Physics is learning how to communicate with ones
environment so that it will talk back.


-----Original Message-----
From: tap-l-owner@lists.ncsu.edu
[mailto:tap-l-owner@lists.ncsu.edu] On Behalf Of
Richard Berg
Sent: Wednesday, October 22, 2008 8:41 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] New member of PIRA seeks some
advice... (fwd) and

Dick,

The procedure that you are suggesting IS additive
color mixing. The
problem is that you are using the wrong primary
colors. You would in fact
get various color mixes, but they would be hard to
decipher and explain.
The important thing about choosing red, green and
blue as the additive
primaries is that they can be produced as very
narrow bands and they are
at the extremes of the chromaticity diagram.

For example, cyan is white with the red removed,
magenta is white with the
green removed, and yellow is white with the blue
removed. So shining the
cyan and the magenta filters on the same spot
would produce white with
some red and some green removed, or a very washed
out blue. Shining the
magenta and the yellow filters on the same spot
would produce very washed
out red color.

If you use spectral yellow and cyan this would be
different, but there is
no such thing as spectral magenta.

You might review some of the demos in our COLOR
indes:
http://www.physics.umd.edu/lecdem/services/demos/d
emosn3/demosn3.htm

We do have a demo of color mixing using dichroic
lights,
http://www.physics.umd.edu/lecdem/services/demos/d
emosn3/n3-03.htm

but as I recall they create broad band colors and
it is not nearly as
effective as high quality strictly additive
filters. According to the
Wikipedia these filters should have fairly narrow
spectra and therefore be
good in an additive process, but my experience is
that they don't work as
well.

Dick


On Wed, 22 Oct 2008, Richard Heckathorn wrote:

> Greetings,
>
> I meant shining light through each of the
filters,
> cyan, magenta, and yellow and reflecting them
back
> on each other. Would that not be adding colors?
>
> Dick H
>
>
> Helping teachers who facilitate, motivating
> students who learn.
> Dick Heckathorn 14665 Pawnee Trail Middleburg
> Hts, OH 44130 440-826-0834
> http://web.cvcaroyals.org/~rheckathorn/
> Adjunct Physics Teacher - Baldwin Wallace
College
> Physics is learning how to communicate with ones
> environment so that it will talk back.
>
>
> -----Original Message-----
> From: tap-l-owner@lists.ncsu.edu
> [mailto:tap-l-owner@lists.ncsu.edu] On Behalf Of
> Richard Berg
> Sent: Wednesday, October 22, 2008 4:03 PM
> To: Tap-L
> Subject: Re: [tap-l] New member of PIRA seeks
some
> advice... (fwd) and
>
> These are subtractive colors. There is not even
> such a thing as an
> "additive" magenta filter. If this works for
> color mixing of lights it is
> strictly fortuitous.
>
> Dick
>
> On Wed, 22 Oct 2008, Miglus, Vacek wrote:
>
>> On 10/22/08 3:05 PM, "Richard Heckathorn"
> wrote:
>>
>>> Question?
>>>
>>> What colors do you get by combining Yellow
> #104, Magenta #128 and Cyan
>>> #116 Ignore filter names, just use
the
> numbers
>>>
>>> Enjoy
>>>
>>
>> Subtractive or additive combinations?
>> :-)
>>
>> Vacek
>>
>>
>>
>
>
**************************************************
> *********************
> Dr. Richard E. Berg, Professor of the Practice
> Director, Physics Lecture-Demonstration Facility
> U.S. mail address:
> Department of Physics
> University of Maryland
> College Park, MD 20742-4111
> Phone: (301) 405-5994
> FAX: (301) 314-9525
> e-mail reberg@umd.edu
> www.physics.umd.edu/lecdem
>
**************************************************
> *********************
>
>
>
>

**************************************************
*********************
Dr. Richard E. Berg, Professor of the Practice
Director, Physics Lecture-Demonstration Facility
U.S. mail address:
Department of Physics
University of Maryland
College Park, MD 20742-4111
Phone: (301) 405-5994
FAX: (301) 314-9525
e-mail reberg@umd.edu
www.physics.umd.edu/lecdem
**************************************************
*********************






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