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Digital Cameras
Ansel Adams, www.wisconsinhistory.org
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Cameras
Effect Cause
Perspective Lens, Focal length
Focus Motion
Field of view Film size,
focal length
Exposure Film speed, aperture,
shutter
Depth of field Aperture,
focal length
Motion blur Shutter
Reference: Photography, B. London and J. Upton
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Pinhole Camera
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Pinhole Camera
Camera Obscura
Cliff House, San Francison
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Field of View
Redrawn from Kingslake,
Optics in Photography
tan2
fov filmsize
f=
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Field of View
From London and Upton
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Field of View
From London and Upton
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Perspective Projection
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Translations
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Translations
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Homogenous Coordinates
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Perspective Matrix
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Perspective Frustum
glFrustum(float l, r, b, t, n, f);
2nr l
0r + lr l
0
02nt b
t + bt b
0
0 0f + n
f n
2 fn
f n0 0 1 0
(r,b,n)
(l.b,n)
(l,t,n)
(r,t,n)
(r*f/n,b*f/n,f)
(l*f/n,b*f/n,f)
(l*f/n,t*f/n,f)
(r*f/n,t*f/n,f)
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Orthographic Transformation
glOrtho(float l, r, b, t, n, f);
2r l
0 0r + lr l
02t b
0t + bt b
0 02
f n
f + n
f n0 0 0 1
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Viewing Coordinate Systems
World
Camera
Screen or Window
Raster or Device
Object or Modeling
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Projection and Modeling in OpenGL
glViewport(0,0,w,h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
glMatrixMode (GL_MODELVIEW);
glLoadIdentity ();
…
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Lenses
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Gauss’ Ray Tracing Construction
Parallel Ray
Focal RayChief Ray
Object Image
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Conjugate Points
To focus: move lens relative to backplane
Horizontal rays converge on focal point in the focal plane
1 1 1
z z f= +
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Depth of Field
From London and Upton
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Circle of Confusion
d
a
c d s z
a z z= =
ssz z
c
Circle of confusion proportional
to the size of the aperture
Focal Plane Back Plane
Sensors
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
CCDs
Developed by Willard Boyle (L) and George Smith (R)
at Bell Labs in 1969
Received NAE Draper Prize in 2006
CS148 Lecture 10 Pat Hanrahan, Winter 2007
CCDs
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
CMOS
http://www.micron.com/innovations/imaging/pixel
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Sensor Size
35mm SLR : 36mm x 24mm
APS: 24mm x 16mm
Increases focal length by 1.5x
1/4” & 1/3”
Point and shoot
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CS148 Lecture 10 Pat Hanrahan, Winter 2007
Pixel Resolution and Size
6 MegaPixel Sensor
35mm
~10um pixels
Efficiently gather light
Low signal to noise
1/4”
~1.5um pixels
Less efficient
More noise
CS148 Lecture 10 Pat Hanrahan, Winter 2007
Bayer Mosaic
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