physics 1230: light and color ivan i. smalyukh, instructor
DESCRIPTION
Office: Gamow Tower, F-521 Email: [email protected] Phone: 303-492-7277 Lectures: Tuesdays & Thursdays, 3:30 PM - 4:45 PM Office hours: Mondays & Fridays, 3:30 PM – 4:30 PM TA: Jhih-An Yang [email protected]. - PowerPoint PPT PresentationTRANSCRIPT
Physics 1230: Light and ColorIvan I. Smalyukh, Instructor
Office: Gamow Tower, F-521Email:
Phone: 303-492-7277
Lectures: Tuesdays & Thursdays,
3:30 PM - 4:45 PMOffice hours:
Mondays & Fridays, 3:30 PM – 4:30 PM
TA: Jhih-An Yang [email protected]
Class # 14
Chapter #4: Cameras & Photography
2
Equivalent exposure settings (same light)
¼ sec. lets subjects move
Background in focus(good depth of field)
1/250 sec. stops motion
Background out of focus
3
Which f-number gives half the light of f-4?
A. f-2B. f-2.8C. f-4D. f-5.6E. f-8
f = F/D, so you need a LARGER f-number for less light. 5.6 is sqrt(2) smaller than 4, so twice the light.
4
Which pair gives the same amount of light?
1/30 sec. and f number 4 and
a) 1/120 sec. and f-1b) 1/120 sec. and f-2c) 1/120 sec. and f-4
4x more light for ¼ the time.
55
Lec. 9: Ch. 4 –The Camera and Photography\
Camera partsLenses for camerasControlling light
Photography as artPhotography as science
We are
here
5
66
Albert Bierstadt
Looking Down Yosemite ValleyOil painting
1865
77
Ansel Adams
88
William Henry Jackson. Mountain of the Holy Cross. 1873.
Photography replaced paintingto describe the western US
Albert Bierstadt
Looking Down Yosemite ValleyOil painting
1865
99
Wright Bros., 1903
Photography as proof. Jackalope, 2003?
1010
Alfred Stieglitz1864-1946Photography as art
1111
Edward Steichen,1879-1973Glamour photography
12
Edward Weston
1886-1958
Compare to 15th century painting with folded cloth
13
Imogen Cunningham1883-1976
Ansel Adams by Cunningham
14
“Fine focus”
Means directional lighting
“Soft focus” (not out of focus)
Means diffuse lighting
1515Ansel AdamsSnake River 1942
1616
Lec. 12: Ch. 4 –The Camera and Photography
Camera partsLenses for camerasControlling light
Capturing imagesDigital images
We are
here
16
How do we capture and save the image?
Cameras existed for hundreds of years (pinhole and lens versions)
The revolution (early 19th century) was FILM: The method to store and reproduce the
images.
Nowadays, we rarely use films
17
1818
Ansel Adams
Digital Image Storage: The CCD
19
CCD: “Charge Coupled Device”.Electronic device for storing images
Light sensor area
Wires go to computer memory.
Digital Image Storage: The CCD
20
CCD: “Charge Coupled Device”.Electronic device for storing images
Light sensor area
Notice the colors.
RGB colored filters in front of the sensors. The Bayer filter.
Digital Image Storage: The CCD
21
CCD: “Charge Coupled Device”.Electronic device for storing images
Rectangular array of PIXELs
Typical array is several thousand by several thousand.
1000x1000 = 1,000,000Pixels,OR
1 MegaPixel.
For photography of objects at different distances from us we use
• A. Camera with CCD that has at least 5 megapixels;
• B. Small aperture (large f-number);
• C. Large aperture (small f-number);
• D. Short exposure;• E. A, B, C, & D
For photography of moving objects we use
• A. Camera with CCD that has at least 5 megapixels;
• B. Small aperture (large f-number);
• C. Large aperture (small f-number);
• D. Short exposure and larger aperture;
• E. A, B, C, & D
Extra credit questions
• What settings we use for small depth of field?
• What settings we use to make photos late in the evening (not much light)?
• What would you do to make a photo during a very sunny day?
• Explain how the photo on the left was done
25
Review:
To help you in your preparation for the exam(since many of you find the problems on lenses and curved mirrors somewhat difficult, we briefly review only this part)
Exam time: Regular class time on Tuesday, Oct 11
http://micro.magnet.fsu.edu/primer/java/mirrors/convex.html
30
Ray Tracing: One method to understand spherical mirrors and lenses.
Example:
(A) Or (B):The image is LEFT or RIGHT of the lens. The image is REAL or VIRTUAL.
This device is the ‘magnifying glass’. The image appears larger than the object.
31
Ray Tracing: One method to understand spherical mirrors and lenses.
Example:
What is the magnification?
SO
SI
SI is the image height
SO is the object height
I
O
SM
S Ray tracing plus a ruler to
measure things and you can determine magnification.
Object distance, image distance, focal length
32
XiXo
F
Magnification formula
S0 = object height
Si = image height
Note the similar triangles.
33Demo: big mama lens and bulb
We do the following: Image on opposite side of lens? XI is positive (otherwise negative)Image on opposite side of axis? SI is negative. (otherwise positive) Object lengths are
ALWAYS POSITIVE.
The lens equation:The land of “One-Over-Everything!”
FXX IO
111F = focal length
XO = object distance
XI = image distance
Usually, F and XO are given. We want to find XI OI XFX
111
34
Distant objects: Let Xo be very large, say 1,000,000 meters. Then 1/Xo = 0.000001, which is very small. You can ignore it. Then
FX I
11 For distant objects,
the image is at the focal point(ask a burnt ant)
Demo: find focal length of lenses
35
Exam time: Regular class time on Tuesday, Oct 11
Good luck on the exam!
P.S. At home, go through the Photography guide on the next two slides