Introduction to Engineering
Camera Lab #3 - 1
Agenda
Do parts I and II of the lab
Record data
Answer questions
Tasks I & II
Objective:
Determine some characteristic quantities
associated with the camera.
The focal length (TASK I).
The near and far focusing distances (TASK II).
Focal Length
a
b
Image
f
O
ab / AB = f/H
f = (H * ab) / AB
H
B
A
Object
Imaging Configuration (Top View)
Task I
Task I
Pick the best central image.
Measure “ab” (using the loupe).
Each group member should measure the
length of the subtense bars.
Try not to be biased by the previous
measurements in your group.
Lens
t
H
H'
P
y
F
F'
N'
N
y'
P'
f'
f
x
s
x'
s'
L
Lens Equation
The lens equation relates the focal length
(f), the image distance (s`) and the object
distance (s).
1/f = 1/s + 1/s`
Depth of Field
Depth of Field
The distance in the object space within which the
object point can be moved and still be in
acceptable focus.
pA
qA
a
AN
c
AF
A
af
aN
Depth of field
A
Image plane for
object point A
Circle of confusion
same size at both
apertures
c
Factors Affecting Depth of Field
The focal length (f).
The object distance (s).
The diameter of the aperture stop (D).
The smaller the aperture the larger the depth of
field and focus.
The radius of the acceptable circle of
confusion (u).
Task II
 Sn & Sf → S.
 S & f → S`.
 S , S`& u → f/D (D is the diameter of the
aperture).
 Compare the estimated diameter of the
aperture with diameter of physical aperture.
 Change Sn & Sf until you get a reasonable
diameter of the aperture
Photography
d c
a
b
Image Space
Lens
A
B
C
D
Object Space
Assignment
Read Parts III, IV, and V of the Camera
Lab #3 procedure.
Think about answers to the questions in
those parts.