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	CS 448 - Perspective, lighting, and photography, April 3 , 2008

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Metagoals for this lecture:
	o Consider the "raw materials" of photography:
		- perspective and lighting, a.k.a.
		- geometry and radiometry
	o Look at some of the "problems of photography"
		- composing a shot, changing the perspective,
		- lighting a scene, difficult lighting situations
	o Compare traditional photographic techniques to computer techniques
	o Show examples of great photographs

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==> I didn't quite get to everything in these notes during the class, but I've
    left them in the notes anyway, in case you want to browse on your own.

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		       *** Quick review of perspective ***

Common assumptions:
	1.  Light leaving an object travels in straight lines
	2.  These lines converge to a point (more or less) at the eye
		o both can be verified from simple observation
		o known by ancients

"Natural perspective":
	3a. More distant objects subtend smaller visual angles
		-> drawing from Euclid (3c BC), in Kemp, fig 31, p. 27

"Linear perspective":
	3b. A perspective image is formed by the intersection of these
	    lines with a "picture plane" (the surface of the painting)
		-> drawing from Piero (1474), Kemp, fig. 32, p. 28

Application:
	o Does a pair of lines parallel to the picture plane converge?

		o Consider buildings seen from across the street in wide-angle.

		-> Leonardo's On Painting, p. 63

		-> fish-eye image of Memorial Church

		o In this case, faraway mullions do not shrink on the canvas,
		Q. Yet their visual angle does shrink.  How does this occur?
		A: They shrink when the canvas is viewed.

		==> Demonstrate using Durer's artist's glass

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		      *** Perspective in photography ***

Viewpoint versus field of view:
	o definition parts #1 and #2 say nothing about the lens;
	  for a given viewpoint, all lenses observe the same lines of sight;
	  lenses only narrow the field of view; we'll come back to #3 shortly

	o focal length versus field of view
		-> Hedgecoe, p. 39
		   (we'll derive this relation in a future lecture)

	o zooming versus dollying
		-> Monterey plaza and fountain, Ansel Adams, p. 103
		(I forgot to show this example in class.)

Wide-angle versus narrow-angle images:
	o wide-angle
		o improves coverage
			-> zurich-churches: stpeters-organ (16mm lens) (in ppt)
		o puts you in the picture
			-> Grand Tetons and thistle, Adams, p. 140
		o cause of apparent distortion?
			-> Dubery and Willats, row of columns, p. 84
		o Explanation: objects look distorted only if you are
		not standing at the proper eyepoint

	o extreme wide-angle (a.k.a. fish-eye)
		o creates real distortion
			-> printout of photograph of Nikon 6mm lens on camera
			-> office cubicles, London, p. 47

	o telephoto
		o selects field of view
			-> workers on Golden Gate Bridge, Peterson, p. 57
		o magnifies the background, hence compresses depth
			-> zurich: lake-and-mountains (400mm lens) (in ppt)
		o decreases depth of field (we'll see why later)
			-> seagull ("pool" of in-focus pixels) (in ppt)

	o extreme telephoto
		o creates near-orthographic views
			-> chess board, Hunter & Fuqua, p. 80
		o telescope mounted to a camera
			-> catadioptric lens, Adams, p. 61
			(I skipped this example in class.)

The view camera:
	o sliding the back parallel to the front ("rising front")
		= off-axis projection
			-> London, p. 294
		o eliminates a vanishing point
		o we can replace this with a larger field of view,
		  but we sacriface sensor resolution

	o rotating the back parallel to a scene plane ("swing back")
		= oblique projection
			-> London, p. 295
		o eliminates another vanishing point
		o we can replace this with a perspective warp after-the-fact
			-> zurich/fraumunster-pillars-s (in ptt), cut & paste
			   into Photoshop, perspective warp left side downward,
			   then skew ULC leftward

	o tilting the lens relative to the back rotates the plane of focus
		o Scheimpflug condition: back, lens, and focus planes intersect
			-> whiteboard drawing, proof requires Snell's law
			-> Adams, fig. 10-10, p. 153
		o e.g. to keep ground plane in focus
			-> Adams, fig. 10-9, p. 152
		o or a page of text
			-> London, p. 293
		o we *can't* replace this adjustment with post-processing!

Panoramic cameras:
	o flatback
		o wide film, but otherwise a normal camera
			-> example cameras, Frost, p. 16 
		o linear perspective - straight lines remain straight
			-> two-page panorama of Tuscany, Frost, p. 49

	o swing-lens
		o slit and lens rotates (around first principle point)
			-> example cameras on Frost, p. 33
		o nonlinear perspective - straight lines become curves
			-> San Gimignano, Frost, p. 30

	o rotational (optional)
		o slit and lens rotates, film rotates faster (or slower)
			-> example cameras, Frost, p. 35
		o same as swing-lens, but can produce 360-degree image
			-> Bath, England, Frost, p. 35

	o Omni-directional cameras (i.e. using non-perspective optics)
		will be covered later in the course
	

Other non-perspective cameras:
	o peripheral camera
		o same as rotational, but inward looking
			-> Andrew Davidhazy, Kingslake, p. 25

Extreme cameras:
	o largest
		-> Mammoth, Hope, p. 122,
		   and photograph of train (loose sheet)
	o smallest
		-> unborn child, endoscope with 0.5mm lens, fiber optic light,
		   Hope, p. 77

I would have covered, if I had more time:
	- omni-directional cameras (using non-perspective optics)

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			 *** Photographic lighting ***

Photographic lighting:
	o size (point versus area) and directionality
		-> taxonomy using light field position & direction into 0D-4D,
		   Langer and Zucker, What is a Light Source",
		   Proc. CVPR '97, p. 172, and illustrations

	o number and placement - lighting design is an art
		o size of light: hard versus soft shadows
			-> De Gaulle est mort, Hunter & Fuqua, p. 28 and 30
		o key, fill, accent/rim, etc.
			-> portrait, London, p. 246
		o relative strength among lights, e.g. key:fill
			-> bust, London, p. 235, and face on p. 234
		o angle of light: raking light
			-> needlework, Hunter & Fuqua, p. 58 and 61

	o special problems
		o complex scenes, like architectural interiors
			-> parlor, Kodak, p. 96
		o lighting reflective objects
			-> trumpet, London, p. 249
		o glassware
			-> frontlit, backlit, darkfield, darkfield+highlights,
			   Hunter & Fuqua, p. 144,145,151,158
		o high dynamic range scenes
			-> black and white chesspieces, Hunter & Fuqua, p. 210

	o a quick tangent: the dynamic range of media is low:
		100:1		painter's pigments
		Cowan says:
		10:1		printing
		20:1		paint
		100:1		CRT
		200:1		transparency

	o sidelight: the high dynamic range problem in painting
			-> Sheeler's The Upper Deck (1929),
			   Gardner, p. 1084
				-versus-
			-> Wright's A Philospher Giving a Lecture
			   at the Orrery (1765), Gardner, p. 896
		o high light levels -> at saturation -> compression of contrast
		o low light levels -> at threshold -> expansion of contrast

	o low-light photography
		o long exposures using available light
			-> Big Ben, Frost, p. 73 (10-30 seconds)
		o using flash to turn night into day, i.e. painting with light
			-> railroad car, Frost, p. 178

	o color - spectral variation
		-> Maxfield Parrish's yellow key and blue fill, slipcover
		   use of this color scheme in Toy Story

I would have covered, if I had more time:
	o The zone system

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			     *** Sources cited ***

Perspective:

	Martin Kemp,
	The Science of Art,
	Yale University Press, 1990.

	Allison Cole,
	Perspective,
	Dorling Kindersley, 1992.
		(for Durer's artist's glass)

	Leonardo Da Vinci,
	Leonardo on Painting,
	translated by M. Kemp and M. Walker,
	Yale University Press, 1989.

	Fred Dubery and John Willats,
	Perspective and other drawing systems,
	Van Nostrand Reinhold, 1972, 1983.

Optics for photography:

	Ansel Adams
	The Camera,
	Little, Brown, and Co., 1976.

	Rudolph Kingslake,
	Optics in Photography,
	SPIE Press, 1992.

Photographic technique:

	Barbara London and John Upton,
	Photography, sixth edition,
	HarperCollins, 1997.

	John Hedgecoe,
	The New Manual of Photography's Handbook, third edition,
	Dorling-Kindersley, 2003.

	Lee Frost,
	Panoramic Photography
	David and Charles, 2005.

	Terry Hope,
	Extreme Photography,
	RotoVision, 2004

	Bryan Peterson,
	Learning to See Creatively,
	Watson-Guptill, 1988.

Lighting:

	Langer, M.S., Zucker, S.W.,
	What is a light source?
	Proc. CVPR '97.

	Professional Photographic Illustration,
	Antonio LoSapio, ed., Kodak, 1994.

	Lee Frost,
	The Complete Guide to Night and Low-Light Photography,
	Watson-Guptill, 1999.

	Fil Hunter and Paul Fuqua,
	Light Science & Magic, 2nd edition,
	Focal Press, 1997.

Lighting in art:

	Helen Gardner,
	Art Through the Ages, twelfth edition,
	Wadsworth Publishing, 2004.

	Coy Ludwig,
	Maxfield Parrish,
	Schiffer Publishing, 1997.

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