bASEARTS : Exposure Basics | Exposure and Equivalency | Exposure and Effect:

• Exposure / Reciprocity Law = Intensity (of the lighting conditions) + the Time in which the light act (or is allowed to expose).
• Equivalent Exposures - combinations of shutter speed and aperture values rendering equal exposures but differing optical effects
• Reciprocity Failure - unproportionate responses by either film or sensor due to unusually short or long exposure times.
  
  
• Exposure Control Modes
  
  
  • Program
  • Aperture Priority (Aperture value)
  • Shutter Priority (Time value or S)
  • Manual

6 Controls which Influence Exposure:

• ISO
  • film/sensor sensitivity
• Aperture
• Shutter
• Metering Modes (pattern(muti-point), center weighted, spot) - Correspond to Focusing Modes
  • by effect Tonal Value at point of meter
• Exposure Compensation Value
• White Balance
  

ISO

• sensor sensitivity - lower the iso more light required / longer time value | higher the value less light faster less time required
• (50, 80, 100, 200, 400, 800, 1600, 3200, 25600)
• side effects -lower to higher grain or noise levels respectively

Av/Aperture:

• Depth of Field
• zone of focus
• range of acceptable focus
• speed of lens
  • determined by the largest aperture
• stopping down
  • reducing the size of the aperture
• focal length
  • the distance between the lens and the focal point at which a sharp image of an object at infinity is formed.
  • the distance between the optical center of a lens and the focal point for an object at infinity
• hyperfocal distance
  
  • at any given f-stop, when the lens is focused at infinity, the distance between the camera and the nearest point of acceptable focus is called the hyperfocal distance
• hyperfocal focusing
• used to achieve maximum depth of field to infinity
• focusing the lens at the 1/2 point between the lens and the hyperfocal distance in order to achieve maximum depth of field
• infinity - anything beyond 50 feet.
  
  
• Aperture Priority- user controlled Av/Aperture - shooting mode
  

Tv/Time Value/Shutter speed:

• Stop action/motion
• Blur
• Panning / panoramming
  • pivoting with the motion of the subject.
• camera shake/jitter
• Characteristics which affect blur
  • angle of movement
  • camera to subject distance
  • subject speed
• Flash and stopping motion
  
  
• Shutter Priority - user controlled Tv/shutter - shooting mode

White Balance -

• balances the digital sensor color values with the wavelength of the light source
  
  

• Color Temperature		Light Source
  1000-2000 K		Candlelight
  2500-3500 K		Tungsten Bulb (household variety)
  3000-4000 K		Sunrise/Sunset (clear sky)
  4000-5000 K		Fluorescent Lamps
  5000-5500 K		Electronic Flash
  5000-6500 K		Daylight with Clear Sky (sun overhead)
  6500-8000 K		Moderately Overcast Sky
  9000-10000 K		Shade or Heavily Overcast Sky

  
  

  Supplemental Lecture Illustrations:
  
  Zone System Zone Description : Short Course in Digital Photo, Prentice Hall
  
  

  Sensor Design : Linear Gradient vs. Sensor Response Gradient - see ref. "the practical zone system, Chris Johnson