lesson 2

• Photographic rays


  Radiant electromagnetic energy which travel in wave motion and can be seen by the naked eye
• Four photographic rays of modern photography

  • X-rays - 1-30 nanometers
  • Ultraviolet rays - 30-400 nanometers
  • Visible light - 400-700 nanometers
  • Infrared rays - 700-1000 nanometers
• These four rays are capable of being recorded on sensitized materials
• Primary colors of light

  Blue, green and red
• Additive color mixture

  Using three beams of primary colors of light resulting in secondary colors, cyan, magenta and yellow
• White is the presence of all colors
• Black is the absence of all colors or absence of light
• Subtractive color mixture


  Using three beams of secondary colors to know which is complementary with each other
• Reflection


  The deflection or bouncing back of light when it hits a surface
• Refraction


  The bending of light when passing from one medium to another
• Diffraction


  The bending of light when it hits a sharp edge of an opaque object
• Kinds of objects as to how they behave to light

  • Transparent objects - allow sufficient visible light to pass through them
  • Translucent objects - allow light to pass, but diffuse it sufficiently that objects on the other side may not be clearly distinguished
  • Opaque objects - so greatly diffuse the light that recognizing the object on the other side is very difficult if not impossible
• Natural light sources


  • Sun, moon, stars, other heavenly bodies, lightning, fire, etc.
• Types of natural sunlight

  • Bright sunlight - objects in open space cast a deep and uniform or distinct shadow
  • Hazy sunlight - objects in open space cast a transparent shadow
  • Dull sunlight - objects in open space cast no shadow
  • Cloudy bright - objects in open space cast no shadow but objects at far distance are clearly visible
  • Cloudy dull - objects in open space cast no shadow and visibility of distant objects are already limited
• Artificial light sources


  • Continuous radiation - fluorescent lamp, incandescent lamps, carbon arc lamp, photoflood lamp, gas lamp, etc.
  • Short duration (Flash Unit) - flash bulb, electronic flash