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Post on 10-Aug-2014



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Presentation on digital photography I gave in 2005 at the Saratoga Library.


  • Digital Photography I The Basics Peter Liu Photography kaiscapes .com
  • Photography
    • From two Greek words meaning drawing with light:
      • phos ("light")
      • graphis ("stylus", "paintbrush")
    • Merriam-Webster:
    • The art or process of producing images on a sensitized surface (as a film) by the action of radiant energy and especially light.
  • Photography
    • The art of capturing light as it falls on a subject or scene, and rendering it so that your viewer is moved by the result.
  • Capturing Light
    • Hard Light high contrast, well-defined shadows
  • Capturing Light
    • Soft Light diffused, rich colors
  • Capturing Light
    • Overhead Light harsh shadows
  • Capturing Light
    • Front Light flat, lacks dimension
  • Capturing Light
    • Side Light evokes mood, accentuates shapes
  • Capturing Light
    • Back Light may need to fill, makes silhouettes
  • Capturing Light
    • Overcast Light low contrast, muted shadows, good for detail
  • Characteristics Of Light
    • Quality
      • The smaller the light source, the harder the light appears
      • The larger the light source, the softer the light appears
    • Direction
      • Determines where shadows fall
    • Contrast
      • Difference between the lightest and darkest tones of the subject or image
    • Source
    • Ambient daylight, tungsten, flourescent, firelight
    • Artificial flash, tungsten
    • Intensity
    • Reflectance
      • Reflectivity of the subject
      • Intensity of the light source
      • Angle of view
      • Distance of light source
    • Fall-off
      • Increase distance, decrease light level (Inverse Square Law)
  • Characteristics Of Light
    • Color
    • Mixture of primary colors: Red, Green and Blue varies according to source
    • Warm predominantly red
    • Cool predominantly blue
    • Expressed in Kelvin (K):
      • Incandescent ~ 3000K
      • Fluorescent ~ 4100K
      • Flash ~ 5400K
      • Daylight
        • Direct Sunlight ~ 5200K
        • Cloudy ~ 6000K
        • Shade ~ 8000K
    • Referred to as White Balance in digital photography.
  • White Balance 4100K ( Fluorescent ) 3000K ( Incandescent ) 5200K ( Sunlight ) 8000K ( Shade ) 5400K ( Flash ) 6000K ( Cloudy )
  • Why Are You Telling Us All This??
    • Because good photography depends on being able to execute two things well:
    • Exposure
    • Composition
  • Exposure
    • A combination of three factors sometimes known as the Photographic Triangle:
    • Shutter Speed
    • Aperture
    • ISO
    • Or
    • how quickly light is being captured through how big an opening onto how sensitive a surface
  • Shutter
    • A cameras shutter covers the hole through which light enters to expose the sensor or film.
    The shutter release button causes the shutter to open for a certain amount of time, then close again. Image source: www. howstuffworks .com Image source: VisibleDust
  • Shutter Speed Fast
    • 1/1600 sec., stops action
  • Shutter Speed Slow
    • Silky, cool, edgy effects
    1 sec. 3 sec. 1/3 sec.
  • Shutter Speeds
    • Open too long, photos are washed out (overexposed)
    • Not long enough, photos are too dark (underexposed)
    • Expressed in seconds: 1/8000, 1/4000, 1/2000 1/1000, 1/500, 1/250, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 second, 2 seconds, etc.
    • Each setting is half or double the speed of its neighbor.
    • As the amount of available light decreases by half, the shutter speed needs to slow by double.
    • As the amount of available light increases, the shutter speed needs to increase
  • Aperture
    • The opening through which light enters the camera.
    Sometimes called an iris because it imitates the opening in the human eye. Image source:
  • Aperture
    • The size of the opening is expressed as an f-stop number :
    • Each number represents an opening size that is half or double its neighbor
    • The larger the number, the smaller the opening
    • For all the science types: the f-stop is actually a ratio between the diameter of the aperture in the lens and the focal length of the lens:
      • e.g. f/2 on a 50mm lens says the aperture is 25mm. 50/25 = 2.
      • (Source: A Tedious Explanation of the f/stop by Matthew Cole)
    • For the rest of us: the size of the opening controls the depth of field in the photograph.
  • Aperture And Depth Of Field
    • f/5.6
    • Shallow depth of field
    f/22 Deep depth of field
  • Aperture And Depth Of Field
    • Caused by refraction of the light hitting the edge of the opening
    • Rays scatter and overlap instead of going straight on its way to the sensor or film
    • The camera sees multiple images, resulting in blur.
    • The smaller the opening, the less surface available to scatter the light, resulting in less blur.
    • Bottom line: the aperture is used to control how much of the scene is in focus.
  • Aperture And Shutter Speed
    • The following reciprocals will yield the same exposure:
    • What changes is how much is sharp and in focus.
    1/8 sec. f/22 1/15 sec. f/16 1/30 sec. f/11 1/60 sec. f/8 1/125 sec. f/5.6 1/250 sec. f/4 1/500 sec. f/2.8
  • The Light Meter
    • A device that assesses a scene and figures out the correct exposure
    • Modern cameras have them built-in
    • External handheld models also available
    • Engaged when shutter is pressed halfway
    • Matrix/Evaluative, Center-weighted, Spot metering
    • Looks for 18% Grey or Middle Grey
    • Easily fooled!
  • Tricky Metering Situations
  • Exposure Compensation
    • Used when the light meter is unable to evaluate the exposure as desired, or when correcting by whole stops is too much
    • Usually +/- 2 EV (Exposure Value) in steps of 0.3 EV
    • Available on most cameras
  • ISO
    • Sensitivity of the sensor or film to light
    • Represented by a number assigned by the International Standards Organization (hence, ISO) 100, 200, 400, 800, etc.
    • Again, each number represents double or half the sensitivity of its neighbor (Aint it wonderful!)
    • The higher the number, the more sensitive to light
    • Digital photography is cool because you can change the ISO from shot to shot!
  • Higher ISO = More Noise!
    • ISO 3200
  • So
    • Exposure depends on:
    • Shutter Speed how fast
    • Aperture how much
    • ISO how sensitive
    • And color is a function of:
    • White Balance how hot
  • And
    • Which camera you choose is a function of how much you want control those factors!
  • Cameras
    • Two popular types of cameras on the market for the consumer
    Point-and-shoot SLR (Single-lens Reflex)
  • Cameras
    • Point-and-shoot
    • Viewfinder separate from lens
    • Small and compact
    • Fixed lens
    • Shutter delay
    • Usually fully automatic (some exceptions, like Olympus C-series)
    • SLR (Single-lens Reflex)
    • Based on 35mm design
    • Actual image seen in viewfinder
    • Interchangeable lenses (more flexible composition)
    • Ability to use filters
    • More advanced metering and shutter system
    • Little to no shutter delay
    • Automatic, Program (Scene), Shutter Priority, Aperture Priority and Manual modes
    • Flash hot shoe
    • Pro models may not have pop-up flash or Program (scene) modes
  • Point-and-shoot Anatomy
    • Viewfinder separate from lens (better to use LCD on digital)
    • Actual image (as exposed) is not quite the same as in the viewfinder
    • Much simpler design than SLRs.
    Light Path Lens Camera Body Viewfinder (front) Shutter Sensor or Film Viewfinder Focal Length LCD Screen (Digital)
  • SLR Anatomy
    • Through-the-lens (TTL) viewing (works like a periscope)
    • Actual image (as exposed) is shown in the viewfinder
    • Mirror flips up when the shutter release is pressed, exposing the sensor (and blacking out the viewfinder)
    • Reflex