Image Formation CPSC 453 Fall 2018 Sonny Chan Outline for Today - - PowerPoint PPT Presentation

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Image Formation CPSC 453 Fall 2018 Sonny Chan Outline for Today - - PowerPoint PPT Presentation

Nov 29, 2023 209 likes •714 views

Image Formation CPSC 453 Fall 2018 Sonny Chan Outline for Today The Camera Obscura The geometry of perspective The anatomy of a camera The Camera Obsura ca. 4th century BC Camera Obscura, 1946 San Francisco, California Camera

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Image Formation

CPSC 453 – Fall 2018 Sonny Chan

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Outline for Today

  • The Camera Obscura
  • The geometry of perspective
  • The anatomy of a camera
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The Camera Obsura

  • ca. 4th century BC
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Camera Obscura, 1946

San Francisco, California

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Camera Obscura, 2012

Cheverie, Nova Scotia

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Why is the projected image

upside down?

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Why do we care

about this all this stuff anyway?

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Perspective

a geometric explanation

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One-Point Perspective

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Two-Point Perspective

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Three-Point Perspective

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Three-Point Perspective

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Perspective

is how we see a 3D picture on a 2D image

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A Camera Obscura for photography?

Sharan Pinhole Cameras, Japan

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The Pinhole Camera

What are its key advantages and disadvantages?

[from civilwar150pinholeproject.com]

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The Modern Camera

Pentax Spotmatic, ca. 1960s

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What’s the difference

between the two cameras?

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Lenses

They let us get more light!!!

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  • bject

image

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Try taking a picture…

  • f this “Prairie Chicken”
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Thin Lens Equation

1 S1 + 1 S2 = 1 f

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Focusing

To focus on objects at various distances, move the lens relative to the image/film plane.

[courtesy of P . Hanrahan, Stanford University]

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Circles of Confusion

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  • bject

image circle of confusion

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How big

is your picture?

1 S1 + 1 S2 = 1 f

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What determines your

field of view?

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Putting it all together…

Nikon D3 cutaway

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The Goal

Get as much light onto here as possible!

[from 1derful.info]

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[from pierretoscani.com]

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The image is controlled by

focal length aperture shutter speed film sensitivity lens characteristics

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Focal Length

  • You can’t change the size
  • f your film!
  • nor your image sensor
  • Longer focal length means

moving the film back more

  • Lens pupil gets smaller
  • Longer focal length =

smaller field of view

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Focal Length on a 35mm Frame

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[from digital-photography-student.com]

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Aperture

  • Measured in f-number:
  • ratio of lens focal length to diameter of lens aperture
  • Larger aperture lets more light in, but circle gets bigger
  • result is “depth of field” effect
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[from ormsdirect.co.za]

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Shutter Speed

[courtesy of K. Breeden, Stanford University]

1/10 s 1/125 s 1/1000 s

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Film Sensitivity

ISO 800 ISO 1600 ISO 3200

[courtesy of K. Breeden, Stanford University]

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Lens Characteristics good lens bad lens

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Chromatic Aberration

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In Summary

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Things to Remember

  • The camera obscura, or pinhole camera, allows us to

capture images of the world in perspective

  • Using a lens allows us to gather more light
  • but introduces a plethora of variables to account for
  • focal length, aperture size, shutter speed, and film sensitivity

chiefly determine the appearance of your picture

  • Understanding how real-world images are formed helps

us to synthesize artificial, but realistic digital images