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Greetings from Norfolk
Not true, brightness is a function of energy, not a
function of frequency.
"I have yet to see any problem, however complicated, which when looked at
in
the right way, did not become still more complicated"
Poul
Anderson
----- Original Message -----
Sent: Wednesday, August 24, 2005 4:36
PM
Subject: Re: Question about
polarization
You're a bright lad BobT.
Very well put indeed.
If we want to talk a colour's frequency we need to consider the
brightness because the brighter it gets the more frequencies we're
getting in the mix.
>
Actually, it is all included in the spectrum. Light is just one
component
of a long and continuous spectrum that includes radio,
light, beta,
gamma, and other waves. Being a ham makes the entire
spectrum very
real.
>
> All that changes is the frequency.
Bob
-
Radiometrically you are correct.
- Photometrically you are IMO missing
the point.
Radiometrically we can measure the wavelength, amplitude,
phase,
direction, constancy etc of electromagnetic radiation whether it
be
light, UV, IR by means of it's physical properties
(strictly
interactions) with other physical things.
What we cannot
do is actually measure what it looks like.
"Pure" monochromatic
wavelengths of light (by definition light being
the part of the
electromagnetic spectrum we can see) are generally
seen as coloured
(though not the same by everybody - consider
synaesthesia. :) ... so
there is a one-way relationship. But exactly
the same colour ( a
perceptual thing ) can be experienced by looking
at a mixture of
wavelengths, so you simply cannot make the reverse
association.
Oh
let's quote someone else ... the "Color -
Enpsychlopedia"
http://psychcentral.com/psypsych/Color
"Electromagnetic
radiation is a mixture of radiation of different
wavelengths and
intensities. When this radiation has a wavelength
inside the human
visibility range (approximately from 380 nm to 740
nm), it is called
light. The light's spectrum records each
wavelength's intensity. The full
spectrum of the incoming radiation
from an object determines the visual
appearance of that object,
including its perceived color. As we will see,
there are many more
spectra than color sensations; in fact one may
formally define a color
to be the whole class of spectra which give rise
to the same color
sensation, although any such definition would vary
widely among
different species and also somewhat among
individuals
intraspecifically."
Colour (as we see it) also is
an anomalous beast when it comes to
intensity.
1) A mixture of
wavelengths that looks bright yellow when viewed at
high intensity looks
olive green when less intense. Exactly the same
mixture of wavelengths -
the only physical difference is the total
amplitude. The "standard
observer" charts attempt to address this but
currently only at two
points: photopic and scotopic. The "real world"
is everything in between
as well ...
2) How many colours do you see ? ( Not including white !
)
http://homepage.ntlworld.com/patrick.davies/odd4.htm
Explain
that with simple physics ...
BobT
Herschel Mair
Head
of the Department of Photography,
Higher College of Technology
Muscat
Sultanate of Oman
Adobe Certified
instructor
+ (986) 99899 673
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