Upcoming Classes
Tuesday, Nov. 13th
Lenses and the Eye
Assignment due: Homework #6 (Grid Drawing)
Thursday, Nov. 15th
Optics and Photography
Special Guest: Prof. Brian Taylor, Photography, SJSU
Assignment due:
* Read “The Camera and Photograph, Seeing the Light :
Optics in Nature, Photography, Color, Vision, and Holography,
D. Falk, D. Brill, & D. Stork, Pages 107-117
Upcoming Deadlines
Tuesday, November 15th
Outline of third oral presentation or written
paper
Tuesday, December 4th
Third Set of Oral Presentations
Third term paper (if not presenting)
Oral Presentations (III)
The following persons will give oral presentations
on Tuesday, December 4th :
•
•
•
•
•
Remmel, Katherine
Sugiura, Ayuka
Yamaguchi, Asuka
Zeber, Emily,
Dinh, Phiphi
For everyone else, term paper is due on that date.
Homework 5: Exploratorium
Due Thursday, November 29th
Extra Credit: Beethoven Center
Visit the Beethoven
Center on the Fifth floor
of MLK library.
Take a photo of yourself
with one of the pianos
or harpsichords.
Turn in photo by Thurs.,
Nov. 15th for one quiz
worth of extra credit.
Extra Credit: San Jose Ballet
See a performance of San Jose Ballet in San Jose
Center for Performing Arts (Nov. 15th – 18th ).
Turn in your ticket receipt. Worth one homework
assignment or three quiz/participation credits.
Ramon Moreno in CARMINA BURANA
Quiz
Today’s reading was
on a controversial
theory proposed by
the painter David
Hockney regarding
this painting by Van
Eyck. Briefly, what
is Hockney’s claim?
Ray Tracing
Geometric optics is
the tracing the path
taken by light rays.
Tracing light rays through lenses
Analysis of cast
shadows using ray
tracing
St Joseph the Carpenter, Georges de La Tour, (1654)
Computer Ray Tracing
Ray tracing requires geometric calculations,
which are easily done by computer.
Light source
Computer
Monitor
Object
Tracing light rays from light
source to object to eye
Image created by POV-Ray, a public-domain ray tracing program
Shadows
Size and sharpness of a shadow depends
on size and distance of light source and of
object casting the shadow.
Ray Tracing for Shadows
Trace rays from light source to wall to map out location of
deep shadow (umbra) and fuzzy shadow (penumbra).
Light source
Object
Wall
Penumbra
UMBRA
Penumbra
Inconsistent Shadows
The perspective
in this painting
is pretty good
but what’s
wrong with
the shadows?
The Birth of the Virgin
Fra Carnevale, 1467
Inconsistent Shadows
Rising
shadows?
Downward
shadow?
No shadows?
Long shadows
from left to right
The Birth of the Virgin
Fra Carnevale, 1467
Specular and Diffuse Reflection
Reflection from most surfaces is diffuse, with
incoming light scattered in all directions.
Reflection from mirror surfaces is specular,
with light reflecting in one direction.
Mirror
Diffuse reflection
Specular reflection
Check Yourself
What objects in this room radiate light?
Every object with a temperature radiates so
every object in this room radiates, mostly
infrared light, outside the visible range.
Is the projector screen radiating visible light?
No, it is reflecting light from projector lamp.
Is the screen diffuse or specular reflector?
Diffuse, so that everyone in the room can
see what is projected onto the screen.
Diffuse Surface is Not a Mirror
Light rays diffusely scatter in every direction
from every spot on the surface.
Look at this spot on
a diffuse surface
See a light ray from the
top of your head
reflected from this spot.
Also see light ray from
the tip of your nose
reflected from this spot.
Transparent, Reflecting Surfaces
Water and glass are transparent but reflect
some of the light striking their surface.
Can see some of the riverbed
through the water surface.
Can see inside the cab through the right window.
Strong reflection of the sun on the left window.
One Way Mirror
Discussion
Room (Bright)
Bright Room
GLASS
One way mirror is just clear glass window.
Dark Room
Reflected light from bright room
masks transmitted light from the
darkened observation room
Observation
Room (Dark)
Law of Reflection
Angle of incidence equals angle of reflection
SPECULAR
REFLECTION
Ray Tracing
Light ray from point A is reflected at point B
and arrives at point B.
Notice the relationship between point B (where the ray is reflected to) and
point B’ (where the ray would go if the mirror wasn’t there).
Demo: Who Do You See?
Which person in the front row sees the guy
with the hat (person F) in the mirror?
Person B sees person F (with hat).
A
B
C
D
MIRROR
E
F
Diffuse light
G
Mirror Image Reflection
To observer at point B, the light from point A
seems to come from point A’, within mirror.
Plane (Flat) Mirror
Tracing light rays from original, to mirror, to
eye allows us to construct image.
HAIR
NOSE
CHIN
Image
Original
Mirror
Demo: Pocket Mirror
See full image of your head in a plane mirror
that’s half the size of your head.
Mirror
Original
Image
Image in the Mirror
Image is seen an equal distance from original within a plane mirror.
Velazquez, Venus at her Mirror
Utamaro, Woman Powdering Her Neck
Incorrect
Incorrect
Helmut Newton,
Bergstrom over Paris
Correct
Non-Flat Mirrors
Image in a curved mirror is
distorted from original.
Determine image location
and size by ray tracing
Demo: Convex Mirrors
Mirrored surface on a sphere or similar
rounded shape. Image is smaller & closer.
MC Escher
Hand with
Reflecting
Sphere
Ray Tracing for Convex Mirror
Image in convex mirror is smaller & closer.
Image
Original
Mirror
Image in the Mirror #2
Portrait of Giovanni Arnolfini and his Wife (1434)
by Hubert and Jan van EYCK
Demo: Concave Mirrors
Mirror is on the inner curved
surface of sphere or
similar rounded shape.
Image size and location
depends on object’s
distance from the mirror.
Telescope
Ray Tracing for Concave Mirror
Image in concave mirror is larger when
original is close to the mirror.
Focal
Point
Original
Mirror
Image
The original is closer to the mirror than the focal point.
Ray Tracing for Concave Mirror
Image in a concave mirror is inverted if the original
is far away from the mirror.
Image is formed in front of the mirror, not within it.
Image
Focal
Point
Original
Mirror
Demo: Forming a Real Image
Locate the image formed in front of a concave
mirror using a strong light source and a screen.
Candle
Candle
Image
Screen
Image
Screen
Arnolfini Portrait
Could van Eyck have used a concave mirror
to help him create his masterpiece?
Theoretically yes, but detailed analysis indicates he probably did not.
Next Lecture
Lenses and the Eye
Remember:
Assignment due:
Homework 6 (Grid drawing)