Lesson 1: The Art and Physics of Photography

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Lesson 1The Art and Physics of Photography

• Basic Photography
• MITSAA
• Spring 2003
• Rob Zehner

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General Info

• Instructor Rob Zehner (zehner_at_pobox.com)
• Course web page http//www.robzehner.com/basic_ph
  oto
• Meeting time 700 - 1000 p.m. every Wednesday
• We will meet in front of the SAA office

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Outline

• How the camera works
• lens
• shutter
• aperture
• film
• Some rules of thumb for good photos

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The Camera
image
virtual image
lens
aperture
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The Lens

• Purpose to collect light from the sample and
  focus it on the film plane
• Focal length distance from the lens to the film
  plane (for a single-element lens) when focused at
  infinity
• Longer focal length more magnification

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The Shutter

• Prevents light from reaching the film
• Opens to allow light through
• In most cameras, the shutter is actually two
  pieces of cloth or metal that move across the
  film plane, one after the other
• Shutter speeds are usually reported as reciprocal
  seconds, e.g. 1000 1/1000th sec.

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The Shutter, continued

• Shutter speed determines relative effects of
  motion
• Slow shutter speeds blurry images
• Fast shutter speeds stopped motion
• Rule of thumb 1/60th or faster will eliminate
  the effects of shaky hands
• Also determines film exposure
• 2X shutter speed 1/2 the light to the film
• 1/2 the shutter speed 2x the light to the film

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The Aperture

• Placed at the focal point of the lens
• Typically a circular opening
• Diameter of circle determines amount of light
  that gets to the film
• Reported as f-number - ratio of focal length to
  aperture
• Larger f-number smaller opening

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The Aperture, continued

• Size affects depth of field - distance in front
  of and behind the focal plane that is in focus
• Small apertures (large f number) greater depth
  of field
• Size also affects film exposure
• Increase of 1 stop (x 1.414) 1/2 as much light
• Decrease of 1 stop (?1.414) 2x as much light

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The Film

• The films job is to detect light
• Photons hit the film and promote a reaction
• Film speed is typically reported in ASA
• Higher ASA faster film - needs less light
• Doubling ASA 1 stop less light needed
• Rule of thumb - sunny f16 rule
• Under bright sun, use f16 and 1/ASA shutter
• Generally, film with a higher ASA is grainier

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The Photographic Process

• Film exposure
• Photographic emulsion held inside a camera is
  exposed to light from the subject
• Film developing
• Latent image on the film is processed to give a
  permanent image with negative optical contrast
• Printing
• Light is projected through film onto photographic
  emulsion to produce an enlarged latent image
• Print developing
• Latent image on photographic paper is processed
  to give a permanent, viewable image (positive
  tone)

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Alternatives

• Transparencies (aka slides)
• Photographic film can be processed to produce a
  positive-tone image on film
• Internegatives
• Film images can be transferred at 11 enlargement
  onto other film for creative effects, or to
  produce a print from a positive transparency
• Direct-positive printing processes
• Certain print processes can produce a positive
  print from a positive transparency
• Digital !
• Scanning, digital printing, output to film, etc.

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The Rule of Thirds
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Other tips for good photos

• Use natural light
• Avoid on-camera flash as much as possible
• Find new perspectives
• Move around
• Take horizontal and vertical shots
• Find converging lines
• Play with negative space
• Take candid portraits
• When in doubt, bracket exposures