lec04_cameras - CS6670: Computer Vision Noah Snavely...

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Lecture 4a: Cameras CS6670: Computer Vision Noah Snavely Source: S. Lazebnik
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Reading Szeliski chapter 2.2.3, 2.3
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Image formation Let’s design a camera Idea 1: put a piece of film in front of an object Do we get a reasonable image?
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Pinhole camera Add a barrier to block off most of the rays This reduces blurring The opening known as the aperture How does this transform the image?
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Camera Obscura Basic principle known to Mozi (470 390 BC), Aristotle (384 322 BC) Drawing aid for artists: described by Leonardo da Vinci (1452 1519) Gemma Frisius, 1558 Source: A. Efros
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Camera Obscura
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Home made pinhole camera http://www.debevec.org/Pinhole/ Why so blurry? Slide by A. Efros
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Shrinking the aperture Why not make the aperture as small as possible? Less light gets through Diffraction effects. ..
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Shrinking the aperture
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Adding a lens A lens focuses light onto the film There is a specific distance at which objects are “in focus” other points project to a “circle of confusion” in the image Changing the shape of the lens changes this distance “circle of confusion”
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Lenses A lens focuses parallel rays onto a single focal point focal point at a distance f beyond the plane of the lens (the
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lec04_cameras - CS6670: Computer Vision Noah Snavely...

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