R1, 1-3 Vision and Lighting

• How does the eye send signals?

  The eye is the receiver (encoder) and transmits signals to the brain (decoder) for interpretation
• What are 4 factors affecting visibility of a task?

  1. size
  2. brightness
  3. contrast
  4. time
• how does size affect vision?

  smaller can be brought closer to see it
• how does brightness affect visibility?

  The luminance depends on the intensity of the light striking it and the amount of light reflected towards the eye. Darker objects requires more light to see
• What is luminance?

  how much light bounces off a target area and gets into your eye (reflected light)
• what is contrast and an example of how it impacts visibility?

  the difference in brightness between an object and its immediate background. It's much easier to read black writing on white background than on a darker background
• how does time affect visibility?

  The longer the time allowed to view something, the more easy it is to clearly see it
• What is needed for good lighting system?(2 factors)

  A good quantity and quality of light
• What is light?

  A special form of electromagnetic radiation (electromagnetic waves) that produces the sensation of sight
• If a light source emits radiant energy that is relatively balanced in wavelengths, what colour will it emit?

  White light
• Which colours are the eyes most responsive to?

  yellow-green range
• what are the 3 primary colours?

  red, green and blue
• What do primary colours signify?

  All colours of light can be made by mixing a combination of red, green and blue
• What is colour temperature or chromaticity?

  A measurement of light quality (appearance). Blue is described as cool, but has a very high colour temperature. A candle flame and low-pressure sodium are described as warm but have a lower colour temperature
• What is CRI?

  Colour rendering index - colour rendition is the ability of a light source to portray the colour appearance of objects accurately when compared to a standard (reference index) light source of the same colour. Scale is 0-100, where 100 means it portrays it most accurately
• What is light measured by?


  Luminous flux (lumen) and luminous flux density (lux)
• What is luminous flux?

  The quantity of light output from a source. Measured in lumens
• What is luminous flux density? 


  The density of light flux measured on a surface (also known as illuminance). Unit is the lux (Lx). It tells us how much light is hitting an object
• What devices measures lighting level?

  A photometer
• Which 2 equations deal with lighting calculations?

  Inverse square law and cosine law of incidence
• What is inverse square law?

  Illumination (lux) is inversely proportional to the square of the distance between the light source and the work surface. E = I / d^2 where E = illumination, I = light intensity, d = distance in m
• What is the cosine law of incidence?

  the illumination on any surface varies as the cosine of the angle of incidence
• What is luminous efficacy?

  The ratio of light output (lumens) to the power input (watts). = lumens / watt. It shows efficiency of the light source to convert electrical energy into light. Efficiency = (Power out / Power in) x 100
• Which lights have best colour rendition?

  Incandescent
• What is a nanometre?

  1 billionth of a metre
• which light source generally has the highest efficacy?

  High-pressure sodium
• Which factors affect lighting installation choices?

  1. area and type of environment
  2. type of task
  3. architectural and decorative requirements
  4. costs of installation and maintenance
  5. costs of operation
  6. availability
  7. environmental impact
• Which 3 considerations should be used that may affect light quality?

  1. glare
  2. diffusion
  3. colour
• what is glare?

  a level of brightness that interferes with vision and typically causes discomfort or eye fatigue
• How can we mitigate glare?

  1. shielding light source
  2. decreasing contrast b/w source and its surroundings by using light colours on ceilings and walls
  3. repositioning the light source
• What is diffusion?

  the effect of scattering the light into many different directions. It avoids any annoying reflections of light. It will create blurrier shadows
• Which colours are cool?

  blue, white, green
• which colours are warm?

  yellow, red, orange
• How can colour be used to improve quality of light?

  Can colour match to increase visual appeal
• what is seeability?

  the ability to determine detail. Lower CRI levels will generally require higher lighting levels to have the same seeability as higher CRI levels of sources
• What is a luminaire?

  The complete lighting unit consisting of lamps, wiring channel, reflectors, lenses, diffusers and control gear. The purpose is to provide the appropriate distribution of light
• How are luminaires classified?

  Based on how they distribute light vertically (up or down)
• Which factors would you base luminaire selection on?

  1. luminaire efficiency (% of total lumens emitted by the luminaire compared to total lumens generated by the lamp alone)
  2. coefficient of utilization (% of the initial lamp lumens that reach the task area to produce illumination)
  3. spacing-to-mounting height ratio for acceptable uniformity of illumination
• How do you attain even light distribution?

  symmetrical arrangement of luminaires
• What are the choices for luminaire light sources?

  1. incandescent
  2. fluorescent
  3. High-intensity discharge (HID)
  4. LED