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New Presentation,
Optical Society Topical
Meeting in Seattle, 2014 July
14, 08:30
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I was an invited
speaker at "Imaging
Systems and Applications (IS),"
sponsored by The Optical Society
of America. There were 22
invited speakers for the IS
meeting, one of 6 topical
meetings at the Sheraton Seattle
Hotel, Seattle, Washington, USA,
2014 July 13-17. My time slot
was Monday, July 14, 08:30 to
9:00 AM. Here are 4
written components from the
presentation:
- The
proceedings article, "Two
Applications of Vectorial
Color: Camera Design and
Lighting of Colored
Objects." The final
version as submitted
is available now. (That link
gives you a free, legal
copy. However, you can
view the related Optics
Infobase Page.)
- Part
of the talk described the
history of science from
Galileo to the present, with
emphasis on the big bang of
engineering at the beginning
of the 20th
century. The historical
narrative is based on an
extended chronology that was
prepared first as a long web
page and is now
available. The extended
chronology is an
important supplement to the
proceedings article.
- The visual
materials of the talk were
prepared as a long web page (rather
than slides). Please take a
look. Again, please click
to see the Seattle talk.
- Leaving no stone
unturned, here is the
script that I read: "Oral
Presentation - 2
applications"
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Vectorial Color
Short Course
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| I presented a short
course on Vectorial
Color at the
Color Imaging Conference 15 in
2007 (Albuquerque) and at CIC 16
in 2008 (Portland, Oregon). On
those occasions, it was a
two-hour class, with no break
and limited opportunity for
questions. Detailed materials
are here
on the web. Now the basics
and applications are published
in two articles (see below), but
the short course would still be
stimulating. I would be happy to
give the course to a small group
in an industrial or academic
setting, with more time for
questions. Then if some are
interested in lighting, camera
design, or other applications,
we could discuss those things.
The country code is 1, the phone
number is above. My Skype name
is jimworthey
. (If we don't answer
the phone, please leave a
voice message and I'll call
you.)
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| Vectorial
Color |
 Why
are the dots on a
TV screen red,
green, and blue?
You could say
"Well, the eye has
red, green and
blue receptors, so
there you are."
That idea is
correct as far as
it goes, but it
skims over
details, like the
fact that red
cones are most
sensitive in the
yellow.
Confronting the
details leads to a
practical new
formulation for
the facts of color
mixing.
Traditional
textbook color
deals with a color
vector [X Y Z],
but the XYZ system
impedes the use of
vector concepts.
One benefit of the
new formulation is
that it makes the
notion of color
vectors more
intuitive and
practical, so the
new work can be
called "Vectorial
Color." It merges
ideas from
William A.
Thornton, Jozef B.
Cohen, Michael H.
Brill, Sherman Lee
Guth, Tom N.
Cornsweet, James
A. Worthey and
others into a set
of 3
color-matching
functions and
related methods.
The materials
linked below
explain vectorial
color, and include
supplementary
material for
formal
publications
appearing
elsewhere.
Supplementary
Materials
for Vectorial
Color
1. Locus of
Unit
Monochromats:
Orthonormal
functions
graph and VRML
(virtual
reality)
presentation of
the Locus of
Unit
Monochromats.
2. CMFs:
The results of a
color-matching
experiment depend
on the choice of
primary
wavelengths.
Nonetheless, the
results---the
color matching
functions---tend
to peak at certain
fixed wavelengths.
To make this
discovery for
yourself, watch
the animated
color matching
functions.
3. Orthonormal
Color
Functions:
Animated
version
of Figures 6 and
7 in "Vectorial
Color."
4. Classic
Idea: An
early concept of "Strength of Action in Mixtures,"
published by
MacAdam and
Thornton, but now
presented in
animated form.
5. Numerical
Data:
Tabulation of
orthonormal color
matching
functions: Work
with
them yourself!
6. Computing:
Programming
for
color using
O-Matrix.
7. Q
and A:
Some questions
and detailed
answers
about Matrix R.
Complete
Papers about
Vectorial Color
Fundamentals
and applications
have been
published as two
articles:
1.
Preprint of
article "Vectorial Color" and the Figures
to go with it. The
whole story is
here (28 pages +
16 figures).
Please be sure to
download the figures
in
addition to the
text. The
published version
is: James A.
Worthey,
“Vectorial color,”
Color Research
and Application,
37(6):394-409
( December
2012). http://onlinelibrary.wiley.com/doi/10.1002/col.20724/abstract
2.
Also
published:
"Applications of Vectorial Color," and the figures for this article. There are
6
applications,
including
information
transmission,
camera design,
machine
vision, and
dichromacy.
The published
version is:
James A.
Worthey,
“Applications
of vectorial
color,” Color
Research and
Application,
37(6):410-423
(December
2012). http://onlinelibrary.wiley.com/doi/10.1002/col.20723/abstract
3.
Mike Brill
comment: Michael
H. Brill,
“Fit-first to be
tied,” Color
Research and
Application,
37(6):423
(December 2012).
<Digital
versions of the
published
articles may be
available from
Jim Worthey.>
4.
CIC 12:
Self-contained
paper Color
Matching
with Amplitude
not Left Out, as
presented at Color
Imaging
Conference 12,
in Scottsdale,
Arizona, USA, in
2004 November. This
discussion of
color
amplitude
seemed to play
well with the
audience
at the time.
More CIC
12: The graphical
material for
the oral
presentation
in Scottsdale
and the
speech as it
was read.
The graphical
presentation is
a long web page
with animated
and
3-dimensional
materials. It
should be
stimulating even
if it's not
totally
self-explanatory.
5. Color
Rendering with
emphasis on LEDs,
light emitting
diodes :
In 2006
February,
there was a Lighting
and Color
Conference in
Orlando,
Florida.
Jim Worthey made
a presentation
called "How
White Light
Works."
At this link
you'll find the
graphical
material for
"How White
Light Works"
as presented at
the conference.
The beginning of
the page is
similar to the
talk of 2004
November.
However, the
Quick Example of
color shifts
under mercury
light is new,
and farther
along are some
detailed
examples, mostly
involving LED
lights. A
first attempt at
combining LEDs
to make white
light falls
short on
red-green
contrast. The
vector
composition
graphs show it,
and the light's
effect on object
colors (64
Munsell chips)
confirms it. A
second attempt
gives too much
red-green
contrast, and
the third try is
"just right."
The third LED
combo does not
track the
blackbody
spectrum
perfectly, but
succeeds in a
more subtle way.
All the graphs
are in Cohen's
space, and
represent
detailed facts
about color
stimuli. The
pictures with
colored borders
are links to
more detail. You
can jump
directly to
the color
rendering
examples.
6. CIC 14,
Camera Sensors:
A 6-page
article, Camera
Design
Using Locus of
Unit
Monochromats,
by Worthey and
Brill, prepared
for Color
Imaging
Conference 14,
to be held in
Scottsdale,
Arizona, 2006
November 6-10. A
web page has Further Examples of Camera Design Using
LUM. The
Further Examples
page has links
to a page about
computer
programming, or
you can jump
directly there.
The poster
itself is almost
ready: CIC14
Poster. As
an alternative,
see the Overview
Page,
which lists
all the
"camera
design" links
.
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Cartoon "Ghosts," from Chris
Harding's "We The Robots"
web site, http://www.wetherobots.com
, 2008 September 26:
Bob's arm
doesn't cast a
shadow.
In Bob's office,
shiny objects lack
highlights and their
details are hidden
by veiling
reflections. Read
more...
Lighting
Quality and
Light Source
Size.
|
 How
do
we see the shape
of a shiny object?
What causes the
dappled sunlight
in the shade of a
tree? Suppose it
is a sunny
afternoon and you
stand outside a
store or school
with fluorescent
lighting. Looking
in the window, you
see that the
fluorescent-lit
interior looks
washed out. Why is
that? No
mystery! It looks
washed out because
it is
washed out. It is
obvious that some
light sources are
small and bright,
while others are
large and
comparatively dim.
This variation has
effects which are
seldom discussed
in clear language.
A 1990 article
addresses these
topics, and now in
2005 January, the
article is
available as a
web page:
"Lighting
quality and
light source
size," Journal
of the IES
19(2):142-148
(Summer
1990). |
| Color
Rendering |
| Two
color rendering
articles have been
published in Color
Research
and Application,
in the last issue
of 2003 and the
first issue of
2004. The pdf
files below (for Adobe
Acrobat Reader
) contain the
final versions as
submitted. |
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Introductory
Article
If a
source emits
light within a
single narrow
band of
wavelengths,
color vision is
lost. An example
is low-pressure
sodium vapor
lights, which
are occasionally
used to light
streets or
parking lots.
Now suppose that
a light would
emit in two
narrow bands.
There is no
example of a
familiar light
with two
extremely narrow
bands, but many
lights tend in
the direction of
two bands. They
are rich in
yellow and blue,
but fall short
in the red and
the green. The
curious fact is
that a light can
be deficient in
red and green
and yet have a
white
appearance—any
shade of white
that you like.
To give good
color contrasts
to objects, a
light must
contain red and
green and blue.
This should not
be a surprise,
because a TV
screen has red,
green and blue
phosphors, the
primary colors
of the TV
palette. Dr.
William Thornton
calls the key
wavelengths the
Prime Colors,
and pins them
down at 450 nm,
540 nm, and 610
nm.
This
introductory
article asks:
"How does color
rendering arise
as a practical
problem?" and
"How do Prime
Colors relate to
other ideas,
such as Matrix
R, and Opponent
Colors?"
Detailed
graphical
examples are
presented. The
figures are in
a separate
file from the
text!
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New
calculation
for
color
rendering
An
opponent method
is appropriate
to the
color-rendering
discussion
because it
brings to the
surface the
notion of
chromatic color,
meaning actual
departure from
white or gray.
In this article,
an opponent
method expresses
the
predictability
of object
colors, and
leads to a
matrix
formulation that
serves two
purposes. The
effects of
replacing a
light L1 by
another L2 are
estimated with a
3x3 “rendering
matrix” P. Given
an object’s
tristimulus
vector under L1,
the method makes
an approximate
prediction of
the new
tristimulus
vector under L2.
Thanks to the
opponent
formulation,
matrix element
P22 quantifies
the gain or loss
of redness and
greenness, while
P33 expresses
gain or loss of
blueness and
yellowness.
These in fact
are major
effects, so the
method predicts
color changes
item by item,
and also in more
general terms. The
figures are in
a separate
file from the
text!
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| 30
(approximately)
New Ideas in
the 2 Articles
Above |
| The
discussion of
lighting is often
burdened with
preconceived ideas
and hidden
assumptions. In
the two articles
above, I use prior
research, but
throw out the
hidden assumptions
in favor of more
rational ideas. In
the 2 articles are
about 30
new ideas,
which are now
listed on a web
page of new ideas.
Most of these are
not entirely new,
but are old ideas
often overlooked
in the discussion
of lighting and
applied color. |
| Linear
Models and the
Mean Vector |
It is
often desired to
represent object
colors or lights
by a linear model
with only a few
terms, perhaps 3
or 4 terms. For
example, the color
rendering article
above uses a
3-term model to
model all object
spectral
reflectances. To
get such a model
from data, it is
convenient to use
Principal
Components
Analysis. Such an
analysis expresses
a population of
data as a mean
vector plus a set
of basis vectors,
each times a
coefficient. This
new research by
Michael Brill and
me discusses the
role of the mean
vector and shows
that it can
sometimes be left
out of the model.
This article has
been accepted for
publication in Color
Research and
Application.
| Read
the
preprint of
Linear
Models
and the Mean
Vector: |
download article - PDF (259 KB) |
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| Basic
Facts, New
Ideas, etc. |
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Prepaid
mobile phone service
with
Lycamobile
.
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For years, some space on
this web page was used to
promote cheap
long-distance phone
service. It was intended
as a business venture,
although I never made a
penny. "Long distance" is
an archaic concept now,
but here's another idea:
prepaid cell phone
service.
A new carrier
called Lycamobile entered the USA
market in early 2013. Lyca
operates out of the UK and
is established in 17
countries now. They offer
monthly plans, but the
pay-as-you-go pricing is
low and easy to
understand:
Domestic
voice calls: 5˘/minute
.
Text messages: 4 cents
each to send, free to
receive.
Data: 6˘/megabyte .
Overseas calls to many
countries: 1˘ additional,
meaning 6˘/min
to call China,
Germany, Austria,
Australia, UK and many
others.
Calls to cell phones are
often more and some
countries are much higher.
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Articles
about
Theory
and the role
of Obvious
Issues:
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To
study the
fundamentals of a
topic, it is often
necessary to study
things that are obvious.
Fairly obvious
facts are
belabored in
Physics and in
Machine Vision
research, for
example. So-called
lighting experts
resist talking
about the obvious,
which prompted me
to write three
articles. Click for
each pdf:
"The role of theory in lighting
research and
design," Lighting
Design and
Application
21(7):15-17
(July,
1991).
"Dealing with obvious issues in
lighting," Lighting
Design and
Application
21(8):15-19
(August
1991).
"Lighting research and theory
can create
business
prospects,"
Lighting
Design and
Application
21(9):14-17
(September
1991).
Did I turn any
lighting experts
into physicists?
Not that I am
aware of. But
please read the
articles.
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Render
Asking:
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Color
rendering:
asking the
question
download
text - PDF
(77 KB)
download
figures -
PDF (210 KB)
Please be
sure to get the figures, which are separate from the
text.
This is a preprint
of an article
published in Color
Research and
Application
© 2003 Wiley
Periodicals, Inc.
James A. Worthey,
"Color Rendering:
Asking the
Question," Color
Research and
Application
28(6):403-412,
December
2003. The article
as published is
available for a
fee at http://www.interscience.wiley.com
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| Render
Calc: |
Color
rendering,
a new
calculation
that estimates
colorimetric
shifts
download
text - PDF
(244 KB)
download
figures -
PDF (139 KB)
Please be
sure to get the figures, which are separate from the
text. This
is a preprint of
an article
published in Color
Research and
Application
© 2004 Wiley
Periodicals, Inc.
James A. Worthey,
"Color Rendering,
a new calculation
that estimates
colorimetric
shifts," Color
Research and
Application
29(1):43-56,
February 2004. The
article as
published is
available for a
fee at http://www.interscience.wiley.com
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| Linear
Models
and the Mean
Vector: |
Principal
Components
Applied to
Modeling:
Dealing with
the Mean
Vector
download
article -
PDF (259 KB)
This
is a preprint of
an article
published in Color
Research and
Application
© 2004 Wiley
Periodicals, Inc.
James A. Worthey
and Michael H.
Brill, "Principal
components applied
to modeling:
dealing with the
mean vector," Color
Research and
Application
29(4):261-266,
August
2004. |
| Problems
viewing
these articles? |
| Some
users have had
trouble in
displaying and
printing the pdf
files. I believe
that I have
resolved these
problems as of
2003 April 16.
Still I would be
happy to hear from
you about color
rendering or pdf
files or anything.
Please email jim@jimworthey.com |
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