Camera Simulation · 2019-04-23 · CS348b Lecture 7 Pat Hanrahan / Matt Pharr, Spring 2019 Camera Simulation References Photography, B. London and J. Upton Optics in Photography,

CS348b Lecture 7 Pat Hanrahan / Matt Pharr, Spring 2019CS348b Lecture 7

Camera Simulation

ReferencesPhotography, B. London and J. UptonOptics in Photography, R. KingslakeThe Camera, The Negative, The Print, A. Adams

Pat Hanrahan / Matt Pharr, Spring 2019

Effect Cause

Field of view Film size, focal length Depth of field Aperture, focal lengthExposure Film speed, aperture, shutterMotion blur Shutter

CS348b Lecture 7 Pat Hanrahan / Matt Pharr, Spring 2019

Cameras (5D integral)


Cook, Porter, Carpenter, 1984 Mitchell, 1991

Depth of FieldMotion Blur


Topics

Lenses

Depth of field

Exposure

Light field cameras


Lenses


Pinhole Camera


From Pharr et al. Physically Based Rendering (3rd Edition)


Lenses Focus!

Rays from a point in object space intersect at a point in image space

These are conjugate points

Points at infinity converge at the focal point or focus

Points on different object planes focus on different image planes

The position of the point of focus can be changed by moving the lens



Gauss’ Ray Tracing Construction


Parallel Ray

Focal Ray Chief Ray

Object Image

Focal Point

http://graphics.stanford.edu/courses/cs178-10/applets/gaussian.html


Snell’s Law



Law of Refraction


Total internal reflection:


Optical Manhole


From Livingston and Lynch

Total internal reflection


Refraction at a Spherical Lens


n : index of refraction


Snell’s Law



Angle of Incidence


The sum of the interior angles is equal to the exterior angle.


Angle of Refraction


Opposite angles are equals


Snell’s Law



Paraxial Approximation: Small Angles


Rays deviate only slightly from the axis


Paraxial Approximation: Small Angles



Angles to Slopes



Gauss’ Formula

Paraxial approximation to Snell’s Law

Ray coordinates


Holds for any height, any ray!


Perspective Transformation

How does z transform?

Represent lens transformation as a 4x4 matrix



Ray Tracing: Finite Aperture

1. Pick a point on image plane x’

2. Pick a point on the lens u

3. Map x’ to x on the focal plane; form ray (u,x-u)


Focal Plane Image PlaneAperture Plane


Real Lens


Cutaway section of a Vivitar Series 1 90mm f/2.5 lensCover photo, Kingslake, Optics in Photography


Double Gauss


Data from W. Smith, Modern Lens Design, p 312


Ray Tracing Through Lenses


From Kolb, Mitchell and Hanrahan (1995)

200 mm telephoto

50 mm double-gauss

35 mm wide-angle

16 mm fisheye


Ray Tracing Through Lenses


From Kolb, Mitchell and Hanrahan (1995)

Depth of Field


Depth of Field


From London and Upton


Circle of Confusion


Circle of confusion proportional to the size of the aperture

Focal Plane Back Plane


Resolving Power

Diffraction limit

35mm film (Leica standard)

CCD/CMOS pixel aperture



Bokeh


Exposure


Image Irradiance



Relative Aperture or F-Stop

F-Number and exposure:

Fstops: 1.4 2 2.8 4.0 5.6 8 11 16 22 32 45 64

1 stop doubles exposure



Camera Exposure

Exposure

Exposure overdetermined

Aperture: f-stop - 1 stop doubles HDecreases depth of field

Shutter: Doubling the open time doubles HIncreases motion blur



Aperture vs Shutter


From London and Upton

f/161/8s

f/41/125s

f/21/500s

Constant Exposure

Light Field Cameras

https://www.wired.com/2011/10/cross-section-shows-lytro-light-field-cameras-insides/

Documents

Camera Simulation · 2019-04-23 · CS348b Lecture 7 Pat Hanrahan / Matt Pharr, Spring 2019 Camera Simulation References Photography, B. London and J. Upton Optics in Photography,