Introduction to computer vision I.5
Jean Ponce
Zuhaib Akhtar za2023@nyu.edu
Ayush Jain aj3152@nyu.edu
Slides will be available after classes
Camera geometry�and calibration
Pinhole Perspective Equation
NOTE: z is always negative..
Affine projection models: Weak perspective projection
is the magnification.
When the scene relief is small compared its distance from the
Camera, m can be taken constant: weak perspective projection.
Affine projection models: Orthographic projection
When the camera is at a
(roughly constant) distance
from the scene, take m=-1.
Strong perspective:
From Zisserman & Hartley
Strong perspective:
Angles are not preserved
The projections of parallel lines intersect at one point
Weak perspective:
Angles are better preserved
The projections of parallel lines are (almost) parallel
Planar pinhole
perspective
Orthographic
projection
Spherical pinhole
perspective
Planar pinhole
perspective
Orthographic
projection
Spherical pinhole
perspective
Diffraction effects
in pinhole
cameras.
Shrinking
pinhole
size
Use a lens!
Lenses
Snell’s law
n1 sin α1 = n2 sin α2
(Descartes’ law
for Frenchies)
Thin Lenses (including paraxial approximation)
Thick Lenses
Spherical
Aberration
Distortion
Chromatic
Aberration
Deblurring and chromatic aberration (Eboli, Sun, Ponce, 2021)
Deblurring and chromatic aberration (Eboli, Sun, Ponce, 2021)
Geometric Distortion
Rectification
Radial Distortion Model
A compound (aka real) lens
E=(Π/4) [ (d/z’)2 cos4α ] L
E=(Π/4) [ (d/z’)2 cos4α ] L
Vignetting
Challenge: Illumination – What is wrong with these pictures?