1. 16421: Vision Sensors Lecture 2: Camera Obscura & View Camera
Instructor: S. Narasimhan
Wean 5310, T-R 1:30pm – 2:50pm

2. Camera Obscura, Gemma Frisius, 1558

3. Pinhole and the Perspective Projection
Is an image being formed
on the screen?
YES! But, not a “clear” one.
(x,y)
screen
scene
image plane
effective focal length, f’
optical
axis y x z
pinhole

4. Pinhole Camera Mathematically: out of all the light
rays in the world, choose the set of
light rays passing through a point
and projecting onto a plane.

5. Pinhole Photography Image Size inversely proportional to Distance
©Charlotte Murray Untitled, 4" x 5" pinhole photograph, 1992
Image Size inversely proportional to Distance
Reading:

6. Magnification y z x d f’ optical axis Pinhole d’ planar sceneB d f’
optical
axis z A
Pinhole A’ d’ x
planar scene
image plane B’
From perspective projection:
Magnification:

7. Pinhole Photography Wide Field of View and Sharp Image
©Clarissa Carnell, Stonehenge, 5" x 7" Gold Toned Printing-Out Paper Pinhole Photograph, 1986

8. Camera Obscura with a Pinhole
Contemporary artist Madison Cawein rented studio space in an old factory building where many of the windows were boarded up or painted over. A random small hole in one of those windows turned one room into a camera obscura.

9. Problems with Pinholes
Pinhole size (aperture) must be
“very small” to obtain a clear image.
However, as pinhole size is made smaller,
less light is received by image plane.
If pinhole is comparable to wavelength
of incoming light, DIFFRACTION blurs
the image!
Sharpest image is obtained when:
pinhole diameter
Example: If f’ = 50mm,
= 600nm (red),
d = 0.36mm

10. Lens Based Camera Obscura, 1568

11. Camera Obscuras with Lenses

12. Charles Schwartz Private Camera Obscura, New York City The optics are housed in a copper turret on the roof and project through a hole in the ceiling onto a 42 inch round white table. At the side of the table are controls for the shutters, the tilt of the mirror and rotation of the turret. It is equipped with an 8-inch lens with a 12 1/2 foot focal length and a 12-inch mirror and brings in a 15-degree slice of the world outside. Sharp focus is possible from infinity to 400 feet. The optics were designed and built by George Keene of California.

13. Eastbourne, England
Edinburgh, Scotland
Kirriemuir, Scotland
1836, Dumfries, Scotland

14. Aberwystweth, Wales
Knighton, Wales

15. Giant Camera, San Francisco, California
Discovery Park, Safford, Arizona

16. George Eastman House, Rochester, New York

17. Image Formation using Lenses
Lenses are used to avoid problems with pinholes.
Ideal Lens: Same projection as pinhole but gathers more light! i o P P’ f
Gaussian Thin Lens Formula:
f is the focal length of the lens – determines the lens’s ability to refract light
f different from the effective focal length f’ discussed before!

18. Aperture, F-Number F-Number (f/#):
Aperture : Diameter D of the lens that is exposed to light.
F-Number (f/#):
For example, if f is 16 times the pupil diameter, then f/#=f/16.
The greater the f/#, the less light per unit area reaches the image plane.
f-stops represent a convenient sequence of f/# in a geometric progression.
Copyright: © Jared C. Benedict.

19. Focus and Defocus Gaussian Law:
aperture
aperture
diameter
Blur Circle, b d
Gaussian Law:
In theory, only one scene plane is in focus.

20. Circle of Confusion
aperture
aperture
diameter
Blur Circle, b d
Blur Circle Diameter b : Derive using similar triangles

21. Depth of Field Range of object distances over which image is
sufficiently well focused.
Range for which blur circle
is less than the resolution
of the sensor.

22. Depth of Field
Both near and farther scene areas are blurred

23. Controlling Depth of Field
Increase Aperture, decrease Depth of Field

24. Large Format (View) Camera

26. [Harold M. Merklinger]

28. Regular Camera: Image, Lens & Object Planes are Parallel
View camera: The image and lens planes can be shifted/tilted
[Harold M. Merklinger]

29. Reflection of Photographer

30. Shifting Lens to Avoid Reflections
Maintains the same perspective as frontal
[Harold M. Merklinger]

31. Focusing on Wall and Floor?

32. Only a necessary condition for focus.
[Harold M. Merklinger]

33. Scheimpflug and Hinge Rules used together for focus
[Harold M. Merklinger]

34. Desargues Theorem
If in a plane two triangles ABC and abc are situated so that the straight lines joining corresponding vertices are concurrent in a point O, then the corresponding sides, if extended, will intersect in three collinear points.
[Robert E. Wheeler]

35. Desargues Theorem and Scheimpflug Rule
SP: Subject Plane
LP: Lens Plane
FP: Image/Film Plane
b: center of projection
Bb: focal length
[Robert E. Wheeler]

37. Depth of Field of a View Camera

38. Depth of Field of a View Camera

39. Focusing Rule for Thick Lenses

40. Paleo-Camera Obscura ?
Small random holes in Paleolithic hide tents coincidentally and occasionally created camera obscuras, which projected moving images inside the dwelling spaces, triggering profound spiritual, philosophical, and aesthetic advances. [

41. Astronomical Camera Obscura?
New World Mission - NASA
200,000 Km