-------------------------------------------------------------------------------

	CS 448 - Perspective, lighting, and photography, January 12, 2006

-------------------------------------------------------------------------------

Metagoals for this lecture:
	o Consider the "raw materials" of photography:
		- perspective and lighting, or
		- 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

-------------------------------------------------------------------------------

==> All .file papers are now accessible in:
	http://graphics.stanford.edu/~levoy/downloaded/...

==> 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.

-------------------------------------------------------------------------------

		       *** 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

-------------------------------------------------------------------------------

		      *** 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 zooming versus dollying
		-> Monterey plaza and fountain, Ansel Adams, p. 103

Wide-angle versus narrow-angle images:
	o wide-angle
		o improves coverage
			-> interior shot, Hedgecoe's Manual, p. 43
		o puts you in the picture
			-> Grand Tetons and thistle, Adams, p. 140

	o extreme wide-angle
		o creates distortion
			-> printout of photograph of Nikon 6mm lens on camera
			-> outstretched arms, Hedgecoe, p. 45

		o cause of distortion?
			-> Dubery and Willats, row of columns
		o Explanation: objects look distorted only if you are
		not standing at the proper eyepoint

	o telephoto
		o selects field of view
			-> workers on Golden Gate Bridge, Peterson, p. 57
		o hides scale
			-> treasury at Petra, Hedgecoe, p. 47, and inset
		o magnifies the background
			-> magnified sun, Hedgecoe, p. 49
		o compresses depth
			-> postcard of MemChu and hills
		o decreases depth of field (we'll see why later)
			-> traditional costume, Hedgecoe, p. 41

	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

The view camera:
		-> general layout, Ansel Adams, p. 30,
		   or just show rented view camera!

	o sliding the back parallel to the front ("rising front")
		= off-axis projection
			-> Adams, p. 143
			-> 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
			-> Adams, p. 144
			-> London, p. 295
		o eliminates another vanishing point
		o we can replace this with a perspective warp after-the-fact
			-> photos/pietrasanta-20nov98/central-view-orig.jpg,
			   edit in Photoshop

	o tilting the lens relative to the back rotates the plane of focus
		o Scheimpflug condition: back, lens, and focus planes intersect
			-> see drawing, proof requires applying 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
			-> My crayon box (Powerpoint slides)
		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
			-> fence, Kingslake, p. 23

	o rotational
		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

Not covered:
	- omni-directional cameras (using non-perspective optics)
	- slit scans: Andrew Davidhazy's web site, Glassner's article
	- other perspective generators, cross-slits, general linear cameras
	- other multiperspectives: Agrawala's paper

Cover in optics:
	- macro lenses (short focusing distance)
	- depth of field

-------------------------------------------------------------------------------

			 *** 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 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 size of light: hard versus soft shadows
			-> De Gaulle est mort, Hunter & Fuqua, p. 28 and 30
		o angle of light: raking light
			-> needleword, Hunter & Fuqua, p. 51 and 61

	o special problems
		o complex scenes, like architectural interiors
			-> parlor, Kodak, p. 96
		o lighting reflective objects
			-> trumpet, London, p. 249
			-> metallic wrapping paper, Hunter & Fuqua, p. 129-131
		o glassware
			-> frontlit, backlit, darkfield, darkfield+highlights,
			   Hunter & Fuqua, p. 144,145,151,158
		o high dynamic range scenes
			-> spatula, Hunter & Fuqua, p. 119

	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 more dynamic range problems:
		o white-on-white
			-> Beethoven bust, Hunter & Fuqua, p. 234-237
		o black-on-black
			-> flashlight on black paper, Hunter & Fuqua, p. 249-51
		o both at once!
			-> black and white chesspieces, Hunter & Fuqua, p. 210

	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
		-> the golden time, woman working on farm, Peterson, p. 127

Separating out the components using computational sensing:
	o without - with polarization to isolate specular reflections
		-> Debevec, Siggraph 2005, fig. 9, p. 763
		o use to improve flash photography?
	o with - without spotlight to eliminate ambient illumination
		-> stmatthew-ambient-elimination.jpg
	o with - without flash to isolate red-eye
		-> Georg Petschnigg's experiment

-------------------------------------------------------------------------------

			     *** Sources cited ***

Perspective:

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

	Allison Cole,
	Perspective,
	Dorling Kindersley, 1992.

Optics for photography:

	Ansel Adams
	The Camera,
	Little, Brown, and Co., 1976.
	(chapter on view-camera adjustments handed out in class)

	Eugene Hecht,
	Optics, second edition,
	Addison-Wesley, 1987.

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

	Rudolph Kingslake,
	Optical System Design,
	Academic Press, 1983.

Photographic technique:

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

	John Hedgecoe,
	The Photographer's Handbook, third edition,
	Alfred A. Knopf, 1993.

	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.

	Debevec, P., Hawkins, T., Tchou, C., Duiker, H.-P.,
	Sarokin, W., Sagar, M.,
	Acquiring the Reflectance Field of a Human Face,
	Proc. Siggraph 2000.

-------------------------------------------------------------------------------