Cameras ! ! First photograph due to Niepce ! ! First on record - - PowerPoint PPT Presentation

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Cameras ! ! First photograph due to Niepce ! ! First on record - - PowerPoint PPT Presentation

Jan 22, 2024 23 likes •286 views

Cameras ! ! First photograph due to Niepce ! ! First on record shown in the book - 1822 ! ! Basic abstraction is the pinhole camera ! ! lenses required to ensure image is not too dark ! ! various other abstractions can be

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Cameras !

  • ! First photograph due to Niepce!
  • ! First on record shown in the book - 1822!
  • ! Basic abstraction is the pinhole camera!

–! lenses required to ensure image is not too dark! –! various other abstractions can be applied!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Image Formation !

  • ! Optics (geometry)!
  • ! Photometry (physics)!
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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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La “camera ottica” !

  • ! Conosciuta sin dall’antichita’ (Aristotele ne

accenna l’esistenza nel 330 a.C.), e’ l’antenato della moderna macchina fotografica!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Camere oscure negli USA !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Camera Obscura, Reinerus Gemma- Frisius, 1544 !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Camera Obscura, Athanasius Kircher, 1646 !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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  • ! Camera oscura a!
  • ! San Francisco!
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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Camere oscure nel mondo … !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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… e in Italia (Rocca di Sanvitale, Fontanellato, Parma) !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Pinhole cameras !

  • ! Abstract camera model -

box with a small hole in it!

  • ! Pinhole cameras work in

practice!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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The equation of projection !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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The equation of projection !

  • ! Cartesian coordinates:!

–! We have, by similar triangles, that (x, y, z) -> (f x/z, f y/z, -f)! –! Ignore the third coordinate, and get!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Geometric properties of projection !

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Points go to points!

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Lines go to lines!

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Planes go to whole image!

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Polygons go to polygons!

  • ! Degenerate cases!

–! line through focal point to point! –! plane through focal point to line!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Polyhedra project to polygons !

  • ! (because lines project to

lines)!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Parallel lines converge !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Distant objects are smaller !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Orthographic projection !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Pinhole too big -! many directions are! averaged, blurring the! image! Pinhole too small-! diffraction effects blur! the image! Generally, pinhole ! cameras are dark, because! a very small set of rays! from a particular point! hits the screen.!

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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The reason for lenses !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Thin lenses !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Basic radiometry !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Cameras !

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Computer Vision - A Modern Approach ! Set: Cameras ! Slides by D.A. Forsyth

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Digital images !