Systems 2 Exam 2 Notes
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. What would you like to do?
Energy in the form of electric and magnetic fields (EMR); optical radiation entering the eye that provides visual sensation.
What does EMR stand for?
electromagnetic radiation (light); it travels at the speed of light
What is the visible spectrum of light?
- (purple) 400 nm - (red) 700 nm (lengths of wavelengths)
- each wavelength has a distinct color
- brain "sees," eyes "detect"
Define what the color rendering index is.
- determines the color you see based on how much of the spectrum is visible
- higher the number, truer the color (1-100)
- Daylight/Incandescent = 100 CRI
- Fluorescent = 70 CRI
- parking lamps are low (yellowish tinge)
What is the correlated color temperature (CCT)?
- A numeric description (in Kelvin) of the color produced by the imbalance of a light source giving off more than one wavelength used to describe fluorescent sources
- Blue to yellow temperature of lamp
- 6000 K (cool), 3000 K (neutral), 2000 K (warm)
Why is light important?
- aesthetic value
How does light affect you? (two ways)
- Visually - sight
- Non-visually - synchronization of circadian rhythms
What is your circadian system and what does it do?
- patterns of behavioral changes over a 24 hour cycle; internal/external forces
- melatonin concentration, controls core body temperature, alertness, sleep/wake cycles
How does light/darkness affect the body? (Name 6 ways)
- 1. Controls hormone production (dopamine, seratonin, cortisol, melatonin)
- 2. Characteristics for circadian regulation differ from those for vision (quantity, distribution, timing, duration, light history, spectrum)
- 3. Affects healthcare and education (increase productivity and learning)
- 4. Daylight can provide visual relief, contact with nature, give time orientation (lack of it = depression)
- 5. Computer work - 8000 K or less light to be less tired at the end of the day (easier to see the screen)
- 6. Optimal daytime office lighting is 8000 K - productivity
What should you base your light choice on?
- occupants need to have a normal circadian cycle
What type of light do you want during the day? At night?
- Day: rich, blue light
- Night: warm light
What CCT values should be used in the work environment? Home environment? Third shift environment?
- Work Environment:
- 5000-6000 K task
- < 8000 K for computers
- Home Environment:
- 5000-6000 K (daytime)
- 2700 K (late afternoon)
- No blue light at night
- Third Shift Environment:
- more blue light
- 8000 K minimum; some reach 12000 K
What is this?
- Virtual Sky by Fraunhofer
- office lighting that emulates natural light
What is the name of the recognized technical authority on light in North America?
Illuminating Engineering Society of North America (IESNA)
What is radiance?
- amount of energy released from a light source
- measure in candlepower or candela
What is the root of the name candlepower?
Candlepower = 1 candle's worth of light
What is illuminance?
amount of light reaching a surface from the light; the number of lumens leaving a source in a specific direction (expressed in foot-candles "fc")
What is existance?
The light leaving a surface with direction
What is the conversion for a foot-candle (used in US) to the unit everyone else uses?
- 1 foot-candle = 10.764 lux (lumes/ square meter)
- A foot candle is the amount of light a source generates 1 foot from candle
What is visual noise?
- interference with desired visual information
- Examples: excessive areas of brightness, reflections, etc
What is a positive affect of blue light?
Helps with acuity of hands and keeps you alert
How quickly do eyes adjust from dark to light? From light to dark?
- Dark to light: 2-3 seconds
- Light to dark: 2-3 minutes
What are controllable aspects of lighting?
- Intensity (brightness vs darkness)
- Texture of light (diffuse vs directional)
- Color of light (cool vs warm or saturated)
What is light responsible for?
- Mood (Active vs relaxed, intimate vs clinical)
- Instruction (way of finding, location/geography, time of day)
For every lighting "mood" there is a corresponding ____ and ____.
light intensity and color
What are behavioral responses to light?
instinctual vs learned/conditional
What is phototropism?
Our "light-responding" instinct; draws people towards light in darkness; affects where people go and how they perceive space
What are the four relationships that best shape our understanding of where light is most effective?
- 1. Adaptation - excess light is wasted
- 2. Brightness - product of contrast; judged by surrounding
- 3. Phototropism - humans notice bright things and ignore dark things
- 4. Vertical vision - vertical surfaces do more to define the impression of space than the horizontal because people tend to notice what is right in front of them
True or false: A few well placed pieces of light can define space as bright.
How can light be applied? (Two steps)
- 1. Light specific surfaces - tasks, accents, local visual effects (draw attention and affect perception of brightness)
- 2. Augment the feeling of brightness (apply light onto vertical and reflective surfaces to increase perceived brightness)
How do you light to choreograph and experience?
use phototropism to lead people from one place to the next, create goals that are obvious destinations, create sub-conscious wayfinding
What are the layers of lighting?
- Light to
- 1. Choreograph an experience
- 2. Define the mood and ambience
- 3. Create accent and visual interest
- 4. Reveal architecture and space
- 5. Allow for specific tasks
How do you use lighting to define the mood and ambience?
relate emotions to qualities of light, use texture [color, intensity]
How do you use lighting to create accent and visual interest?
emphasize important objects, add elements of sparkle, create contrast and variety
How do you use lighting to reveal architecture and space
reveal surfaces to define boundaries or to add volume, confine light to reduce perception
How do you use lighting for specific tasks?
consider more than just sheer quantity, visual comfort for tasks, flexibility for different uses
How do you use lighting to choreograph an experience?
- create obvious destination
- guide people through a space (phototropism)
- subconscious way-finding
What is natural light?
quantity/quality of light available for illumination in a building are determined by regional climatic conditions; dynamic and constantly changing
What are the 3 basic sources of light?
- 1. Daylight - diffused via clouds
- 2. Sunlight - direct
- 3. Reflected light - day or sun light reflected from surface (natural or manmade)
What is the daylight factor (DF)?
- ratio of internal illuminance at a point in a room to the external illuminance; normally taken at horizontal working plane
- DF = (Ei/Eo)100
What are the two major functions of daylight?
- 1. Functional (directed, controlled)
- 2. Decorative (dramatic, impressive, often compromises the usability and comfort, though, for visual impact)
What is visual perception?
Visual perception is a combination of seeing (eyes) and interpreting (brain). Perception of the environment is an active information seeking process.
What is the brightness of an object?
The subjective attribute of how much light is emitted, reflected, transmitted
What is the white dog effect?
- Same reflectance but different in contrast
- as the task increases, the amount of light needed increases
True or false: the older you get, the more light you need.
True or False: Larger surface areas have the highest effective reflectance.
FALSE! Smaller surface areas are more effectively reflective.
What is the solar altitude?
- angle of the sun in relationship to the horizon
What is the solar bearing (azimuth) angle?
sun's location in relationship to south
How is northern light used differently than southern light?
- Northern light: daylight/skylight
- Southern light: direct
What are sunlighting strategies for direct light? (5)
- 1. Shade (shade openings to prevent glare and excessive heat gain)
- 2. Redirect (spread light over large area)
- 3. Control (amount of light required at proper time)
- 4. Efficiency (shape interior and use reflective surfaces)
- 5. Integrate (openings should provide light or a view or shouldn't exist)
What are daylighting strategies for diffused light?
- 1. Maximize solid angle of sky seen from the task of light reflective surfaces
- 2. Shade to prevent glare
- 3. Do not block light (no light-shelves/overhangs)
- 4. Locate openings high (high windows and horizontal skylights)
- 5. Shape space to minimize absorption of light (maximize ceiling height near windows to allow high windows)
How does a building's surroundings impact the light entering?
Solar access denied based on (1) topography [mountains/hills] or (2) urban design [adjacent buildings]
How do you maximize light access?
Maximize building perimeter (use letters like I E O T as shapes to emulate)
What did the old IES standards take into consideration concerning electric lighting?
- time allowed for task
- importance of task
- reflectance of surrounding areas
What do current IES standards take into consideration concerning electric lighting?
- minimizing glare
- evenness, uniformity of light
- background light levels
- color rendering requirements (programmatic specification)
- energy requirements
- controllability (dimming, instant on/off)
- noise requirement (electric lights give off noise)
What ASHRAE Standard is used in electrical lighting design?
189.1 - It is the first code-intended commercial green building standard in the US
What is the light-related criteria in 189.1?
- Light pollution reduction
- lighting power allowance
What are the requirements in 189.1 about occupancy sensors?
now required in certain buildings(offices, classrooms, meeting centers); must turn lighting off within 30 minutes of all occupants leaving a space
How does 189.1 limit exterior signage energy usage?
If on during the day, reduce power by 65% during nighttime hours. If not, reduce 30% after closing and turn off during daytime.
What is daylight harvesting?
electrical lighting must be reduced in response to available daylight either by continuous daylight dimming or a combination of stepped switching and daylight-sensing automatic controls
What is the minimum daylight zone?
At least 50% of the floor area must be in daylight zone.
What is the IgCC?
International Green Construction Code - it contains minimum requirements using both prescription and performance based provisions and works as an overlay to the whole series of international codes
Why do you need to do lighting calculations?
To predict what light equipment will be needed
What are the two methods of light calculations?
- 1 - Lumen - measured light output from source in an arbitrary direction
- 2 - Candela - light intensity in a specific direction from a source
True or False: A light source has 1 lumen value but can emit different candela values in every direction.
How do you work the lumen method?
- 1. Determine the area receiving light
- 2. Define desired illuminance in feet-candles
- 3. Decide how many fixtures you need
Lumens needed = (illuminance)(area)/(coefficient of utilization)(light loss factor)
What is the coefficient of utilization?
a safety factor used in the lumen method; examples include direct fixture, indirect fixture, spot/accent, wash
What is the light loss factor?
a safety factor in the lumen method that accounts for depreciation of lighting system over time; examples: lamp lumen depreciation, lamp dirt depreciation, etc
How do you solve for illuminance using the lumens method? What are the units?
Illuminance (fc) = [(lumens (fcft^2))(area(ft^2))]
How do you solve the candela calculation?
- 1. Define distance.
- 2. Identify candela value of fixture in appropriate direction
- 3. Typically use "center beam candle power" (CBCP)
How do you solve for illuminance using the candela method?
Illuminance = candela value/distance squared
What are electric light sources designed to provide?
- 1. Accurate rendition of color/complete spectrum
- 2. Pleasing color temperature/balance of spectrum
Must consider cost (initial and operating), color rendering index, dimming, instant on and off, heat generated
What type of light bulb is this?
What are electric light sources designed to do?
Provide accurate rendition of color and complete spectrum
What is a halogen incandescent lamp?
It has a small package and is therefore easier to direct. They are popular because they are inexpensive and readily available and have warm color temperatures.
What are the two construction types of halogen incandescent lights?
- 1. Soft diffuse lamps that spread light in every direction
- 2. small sources built into directional lamps
What is an example of an efficient electric light source?
Fluorescent lamp (compact and linear); low temperature and long lasting source with a variety of color rendering properties; cheap
What is high intensity discharge (HID)?
an efficient electric light source that is very efficient, concentrated, high lumen output "directable" source; creates same light texture as halogen sources but more efficient
How can electrical lighting reduce the amount of energy used?
dimming, photo sensors, occupancy sensors
True or False: It is not possible to get direct sun light from the north.
According to the guest speaker, what are the three types of light?
- 1. Natural light
- 2. Performance light
- 3. Electric light
What does a lighting designer's palette include besides light?
What are the three components of a lighting design?
- 1. The concept
- 2. The luminate
- 3. The detail
What would you like to do?
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