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Lesson 1: The Art and Physics of Photography


... rules of thumb for good photos. The Camera. image. lens. aperture ... Other tips for good photos. Use natural light. Avoid on-camera flash as much as possible ... – PowerPoint PPT presentation

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Title: Lesson 1: The Art and Physics of Photography

Lesson 1The Art and Physics of Photography
  • Basic Photography
  • Spring 2003
  • Rob Zehner

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

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

The Camera
virtual image
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
  • Longer focal length more magnification

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.

The Shutter, continued
  • Shutter speed determines relative effects of
  • 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

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
  • Larger f-number smaller opening

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

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

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

  • 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.

The Rule of Thirds
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
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