Visual Communication in Computer Graphics and Art http:www'eagereyes'orgVisComm

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Visual Communicationin Computer Graphicsand Art

• Photography II

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Symbols in Painting
David Bailly, Self-Portrait with Vanitas Symbols,
1651
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Baillys Self-Portrait

• Painted at 65
• Shows his current self in painting-in-painting
• Symbols
• Coins, pearl necklace, wine Fortune
• Skull Science
• Soap bubbles Transience
• Palette Painting
• Whole painting symbolizes transience, time, aging

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Single/Twin Lens Reflex Cameras

• Single Lens Reflex, SLR
• Twin Lens Reflex, TLR

Viewfinder
Viewfinder
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(Dis-)Advantages of SLRs

• Advantages
• Exact framing, no parallax
• Viewfinder image upright and not mirrored
• Can see sharpness, filter effects, etc.
• No inferior lens for viewfinder
• Disadvantages
• Inertia of mirror movement
• No image while picture is taken
• Dark viewfinder with some lenses

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Focal Length and Perspective

• Focal length f determines the image angle ?
• Illustrated for pinhole camera

?
s
f
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Focal Length/Format and Angle
Same length, Different format
Important especially for digital cameraswith
different sensor sizes.Reason for 35mm
equivalent
Same format, Different lenght
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Focal Length/View Angle

• Wide Angle Lens
• 35mm format up to about 35mm
• Deep image
• Differences in size between close and distant
  objects
• Telephoto lens
• 35mm above 85mm
• Compressed image
• All objects have similar size

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Fisheye Lens

• Very wide angle
• More magnification in center of image

http//video.antville.org
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Refraction of Light
Light is changesdirection on theinterface
betweenmediums of differentoptical
density Different wavelengths are refracted
indifferent angles
http//www.uni-bayreuth.de/
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Refraction of Light
a incident angle ß refractive angle c1
speed of light in medium 1 c2 speed of light in
medium 2
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Lens Camera

• Lenses for better light sensitivity and more
  creative control

Lens
Shutter
Aperture
Film
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The Thin Lens Model
Focal Length f
Optical Axis
f
Lens plane
The Lens Equation
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Shallow Depth of Field
David J. Nightingale, chromasia.com/iblog/
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Shallow Depth of Field
John Washington, http//johnwashington.co.uk/
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Aperture
D
f

• Numeric aperture k (the denominator in 1/5.6,
  etc.)
• Effective lens diameter D
• Focal length f

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Aperture

• Part of the lens
• Shape of aperture
• Ideally round
• Really a (more or less) regular polygon
• Important for appearance of blurred regions
• Aperture blades
• Stopping down means closing aperture

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Numeric Aperture

• Number that gives the ratio between effective
  lens diameter and focal length
• Does not describe the ratio of incoming/outgoing
  light!
• Each step means half/double the area, so aperture
  numbers change with v2 1.411, 11.4, 12,
  12.8, 14, 15.6, 18, 111, ...

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Circle of Confusion
C
D
v
Solid line sharp imageDotted Line blurred
image
v
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What is Sharpness?

• Every point is depicted as small disc
• Image appears sharp if circle of confusion small
  enough to be seen as point
• For 35mm and typical enlargements, a diameter of
  less than 0.03mm gives a sharp image

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Circle of Confusion

• In practice mostly a polygon
• Aperture blades rounded
• Diffraction occurs at corners where aperture
  blades meet
• Aperture designed so blades meet at obtuse angle

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Diffraction at Aperture
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Bokeh

• The quality of blurred regions of the image
• Japanese Word
• Relatively subtle in most images
• Criterion for lens quality

http//wvs.topleftpixel.com/
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Sieve Aperture
Heinrich Tauscher
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Mirror Lens

• Aperture has doughnutshape

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Mirror Lens Bokeh