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Grex > Coop10 > #98: Agenda for the 4/22/98 Grex Board of Directors Meeting | |
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janc
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Agenda for the 4/22/98 Grex Board of Directors Meeting
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Apr 15 16:14 UTC 1998 |
Agenda for the 4/22/98 Grex Board of Directors Meeting
0.00000077 Initial Gavel Pounding - janc < 1 minute
0.00000063 Treasurer's Report - aruba 10 minutes
0.00000060 Fund Drive - aruba 15 minutes
0.00000054 Publicity Committee - mta 5 minutes
0.00000049 Technical Committee - staff 10 minutes
0.00000044 New Business - all ???
0.00000041 Final Gavel Pounding - janc < 1 minute
The meeting will be at 7:30pm, probably at the ITI cafeteria (though I still
have to confirm that).
If there are other items that should be on the agenda, please let me know.
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| 44 responses total. |
other
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response 1 of 44:
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Apr 16 15:09 UTC 1998 |
i may not be able to make it, as i am working the Harry Connick, Jr. show at
Hill Auditorium that day. On the other hand, I might be able to make it,
though i would likely have to leave by 9:30...
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janc
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response 2 of 44:
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Apr 21 20:54 UTC 1998 |
Probably we should have another topic on procedures for selling/loaning Grex
equipment. I'm not sure that we wouldn't prefer to let that be discussed more
here on-line before we try to establish procedures for this, but I think we
could reasonably approve selling Scott the monitor.
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janc
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response 3 of 44:
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Apr 21 20:56 UTC 1998 |
What? Nobody guessed the agenda item numbers? Hint: It's another
physics/chemistry thing.
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jared
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response 4 of 44:
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Apr 21 21:01 UTC 1998 |
hrm.. i can get you folks in, but i need to get out by 9:30 at the latest
from iti. There's an important revelation at 10: that i need to see.
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janc
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response 5 of 44:
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Apr 21 21:13 UTC 1998 |
Thanks Jared, that will be fine.
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jep
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response 6 of 44:
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Apr 22 17:08 UTC 1998 |
I haven't the foggiest about the agenda item numbering scheme this time.
It's probably the sizes of atoms in miles across, though, or something
like that. (-:
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valerie
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response 7 of 44:
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Apr 22 22:22 UTC 1998 |
This response has been erased.
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janc
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response 8 of 44:
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Apr 22 22:29 UTC 1998 |
Another hint: The units are meters.
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robh
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response 9 of 44:
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Apr 23 01:03 UTC 1998 |
Given the small amounts (in meters) and the fact that there
are seven of them, I'll guess: the wavelengths of the seven
colors in the visible spectrum.
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albaugh
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response 10 of 44:
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Apr 23 19:50 UTC 1998 |
I would make a snide remark about the foolishness of this item numbering
business, but then I'd have to scribble it... ;-)
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rcurl
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response 11 of 44:
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Apr 24 05:19 UTC 1998 |
How do you pick the 7 colors in the visible spectrum? There are an
infinite number, or referring to the seven simply named colors of
the "verbal spectrum" - has someone actually defined a fixed wavelength
for the center, or mean (arithmetic or geometric or harmonic?) of each?
See, item numbering isn't so foolish as it raises interesting issues
(which some wet blanket will tell us to take elsewhere).
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robh
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response 12 of 44:
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Apr 24 11:53 UTC 1998 |
These are physicists we're talking about, Rane, of course they
think they can define reality with nothing but numbers... >8)
I have vague recollections of seven "official" wavelengths
for the colors on one of those annoying posters in my HS
physics class. Unlike janc, they didn't make us memorize them.
Here's something from a Web page I just snagged:
Approximate wavelengths for various types are:
Wavelength
Type in Centimeters In Å
y-rays 10^-12 to 10^-10 0.01
X-rays 10^-9 to 10^-7 0.1 to 10
Ultraviolet light 10^-6 to 4 X 10^-5 100 to 4,000
Visible light 4 X 10^-5 to 8 X 10^-5 4,000 to 8,000
Infrared light 8 X 10^-5 to 0.1 8,000
Radio waves 1 to 10^5
Note that the visible spectrum is defined as being between
.00004 and .00008 cm - or, between .0000004 and .0000008 meters.
And the range in janc's list is .00000041 to .00000077 meters.
I think I may be on to something.
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mdw
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response 13 of 44:
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Apr 24 16:10 UTC 1998 |
People have studied how many colors are recognized in different
cultures. As it happens, there is actually a great deal of similarity,
which suggests that there is actually a great deal of commonality in the
way we all see colors. There are quite a few interesting exceptions, of
course. Various forms of color blindness are common. There are also
several interesting mutations in color pigments that really can make
colors look "different" to different people. Many of these mutations
are sex linked, which means men are somewhat more likely to see colors
"differently" than women.
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rcurl
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response 14 of 44:
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Apr 24 16:55 UTC 1998 |
We, of course, only see *three* colors - that is, we have three types
of color receptor cells, each of which respond to a narrowed range of
colors (which over lap somewhat). But the brain only receives three
types of stimuli from these cells, and creates all the colors we "see"
from those. This, of course is why only three color guns are needed
in our monitors for "millions of colors".
You are definitely on to something, Rob, but I doubt very much that
real physicists set those numbers, or if they did it was because some
inquiry arose from a layperson (or a secondary school teacher). So
the question is, who chose those arbitrary wavelength values for the
arbitrary seven-color subdivision of the visible spectrum?
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other
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response 15 of 44:
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Apr 24 17:55 UTC 1998 |
janc said something about an ANSI standard....
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rcurl
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response 16 of 44:
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Apr 24 18:03 UTC 1998 |
How is it implemented?
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other
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response 17 of 44:
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Apr 24 18:11 UTC 1998 |
no clue. i suppose to some extent it would have to be completely arbitrary.
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bru
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response 18 of 44:
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Apr 24 20:08 UTC 1998 |
There are only 7 colors that we can see. ROY G BIV or Red, Orange, Yellow,
Green, Blue, Indigo, Violet.
These collors cannot be broken down into sub-colors. That is, a prism will
not break these colors down any farther. If a prism is placed in front of
sunlight, then another prism placed in front of just one of these colors, it
will remain that color.
All other colors are seen only in our minds.
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rcurl
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response 19 of 44:
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Apr 25 05:33 UTC 1998 |
We can "see" only three (3) colors. All others are combinations of those,
according to how the three (3) types of color sensing cells in the eye
are stimulated. We can *distinguish* thousands of colors, but that's
because the brain can distinguish different admixtures of just those three
(3) colors. Haven't you ever looked at a spectrum, bru? There is a
continuous variation of color across it - not seven stripes, each of
a solid color.
I was uncertain what "256 colors", "thousands of colors ('16 bit')"
and "millions of colors ('32 bit')" meant, until I started working with
a video board. It is simple enough. 16 bits can encode 1028 combinations
of the three (3) colors reported to our brain. However I have wondered
what admixtures (relative proportions of the three (3) colors are encoded.
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davel
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response 20 of 44:
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Apr 25 11:48 UTC 1998 |
forget
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janc
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response 21 of 44:
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Apr 25 13:47 UTC 1998 |
The item numbers are the boundaries between the wavelengths of lights
associated with the different colors. They are, of course, not real physical
constants, but rather somebody's guess at where typical human perceptual
boundaries (which are probably at least partly cultural) lie. I've seen
the same table with the same values in several intro physics books, but
this one is from Halliday & Resnick. It is a useful thing for a physicist
to know roughly how frequencies of light map into spectral colors, just as
it is useful to know if she is talking about visible light, x-rays, or
radio (also arbitrary divisions from a purely physical viewpoint).
It's been a while since I taught about color in a computer graphics class,
but no computer can display the full range of colors the human eye can
perceive. The spectrum contains only pure, single frequency colors. Many
things we perceive as different colors are not pure frequences (look for brown
or beige in the spectrum sometime), but mixtures. You can not make all
possible spectra by mixing 3 standard spectra. You can do well enough for
most purposes though.
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mdw
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response 22 of 44:
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Apr 25 14:09 UTC 1998 |
If you pick the *right* 3 colors, the the only colors you can't
reproduce by mixing are way out on the fringes. This problem isn't
restricted to computers - it applies to any color video monitor, and it
also applies in painting, theatrical lighting, textile dyes, or
anywhere.
There are variety of ways computer video systems can represent colors.
However, most common systems today use "color maps", because it is cheap
and extreme versatile. The classical example of this is most "256
color" systems. What most of these systems do is to store bytes in
memory, each byte representing one pixel on the screen. Rather than
directly mapping a numeric byte quantity into an RGB triple, however,
the byte is used to look up a 24 bit quantity in a separate color map --
a separate segment of memory in the video adapter. The 24-bit quantity
is then used to separate distinguish between 256 possible intensities
for each of the electron guns. The quality of the resulting picture can
be *almost* as good as a real 24-bit deep picture, but in addition, it
is also possible to play very interesting animation tricks - by changing
the color map values used, things can be changed very quickly on the
screen without the necessity to redraw things. Newer displays tend to
have more than 8 bits for a pixel, of course, but most still have a
color map that can be changed on the fly.
Even though we know a lot about the biochemistry of the pigments in the
human eye, as it happens, we *still* don't know how color is represented
in the neural signals sent. There are, as a result, a variety of
effects we can't explain scientifically. For instance, certain rapidly
spinning black & white shapes can create the illusion of color to the
human eye.
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robh
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response 23 of 44:
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Apr 25 15:25 UTC 1998 |
So do I win anything for coming the closest to getting it?
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rcurl
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response 24 of 44:
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Apr 25 16:58 UTC 1998 |
You win our eternal (well, temporary) gratitude for stimulating this
fascinating discussion (which, of course, deserves its own item).
Re #21: when I was working with filters, etc, I knew a central wavelength
for the seven "colors", in order to talk about filter choices more easily.
The boundary values are, in the context of seven "colors", not even colors
(since they are between two colors).
Re #22: I don't understand yet...is the "256 colors" coding an 8 bit word?
If so, it can only code for 256 colors, not 256 of each of the three guns,
which would require either 3 8 bit words, or one 10 bit word. I guess I
don't understand the lookup scheme for the 24 bit color map. In addition,
a lot of the combinations from the 24 bit map are the same color - just
different intensities. Is intensity coded separately?
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