06 Flashcards
Lightness
In color theory, lightness is how bright or dark a color is. It is the amount of black or white in color. It is independent of hue and saturation. Also called value.
Hue
Defined by wavelength and what most of us mean when we say “color.”
UV Rays
UV rays, or ultraviolet light, are located between visible light and x-rays on the electromagnetic spectrum. Invisible to the naked eye, UV rays can damage surfaces and cause colors to fade.
Rods and Cones
Photoreceptor cells in the retina of the eye named for their shapes. Rods are very abundant in the human eye, work in low light, and do not see color very well, making everything at night appear grayish. Rods are good at detecting motion. Cones are less abundant, require higher lighting levels to activate, and are closely packed in the fovea, where they are used to perceive color and details.
Layers of light
- General Lighting: fundamental and required by code
- Accent Lighting: creates mood or ambiance
- Task Lighting: localized lighting for any particular task like cooking or reading, for example.
A common error in kitchen and bath lighting design
Placing downlight fixtures in the ceiling behind a person, where their head casts a shadow over what the person is doing.
Dry, Damp, or Wet-Listed
Wet-listed fixtures are for use in areas with direct exposure to water, such as showers or outside in the rain. Damp-listed fixtures are located in areas subject to condensation, like a pool area or bathroom. Listings are provided by the UL. Dry location lights are designated simply as UL-listed.
Estimate the diameter of a pendant for a dining room.
Add the width of the room plus length and make it equal to x. Turn the value of x feet into x inches and that is the diameter of the pendant. For example, imagine a room that is 16’ x 14’. Because 16 + 14 = 30, the pendant should be around 30” in diameter.
Give an example of how the thermal and luminous environments of a building cannot be separated.
- Lighting in commercial buildings is a primary source of heat gain, directly effecting the HVAC system.
- Shading devices designed to limit solar heat gain affect the quality of daylighting.
- When designing for passive solar, one must also consider glare, contrast, and privacy.
Luminance Exitance
The luminous flux density leaving a surface, irrespective of direction viewer position. It is a product of illuminance and reflectance. Unit is lumens per unit of area.
Why are clear skies blue?
As white light from the sun is scattered by oxygen and nitrogen in the atmosphere, the blue wavelength scatters more and this is what makes the sky appear blue.
Why is the sunset shades of red, orange, and yellow?
When the sun is lower in the sky, it travels through more particles that scatter all the shorter blue, green, and violet light; this leaves only the longer wavelength red, orange, yellow light to reach our eyes.
Doppler Effect
The change in a sound frequency due to an observer’s movement.
More than one candlepower distribution curve is needed for __________ (symmetrical/nonsymmetrical) light sources.
Nonsymmetrical.
Fenestration
The entire aperture assembly, including the opening, glazing, and surrounding overhang, and any screens, mullions, louvers, blinds, draperies, etc.
Calculating illuminance
If the number of lumens striking a surface and the area of the surface are known, then the illuminance can be calculated. For example, if 5,500 lumens are striking an area that is 10’ by 10’, then the illumination is 55 foot-candles (fc). This is done by taking the lumens and dividing by the area. 5,500/100 = 55. This does not account for light loss factors.
Visual Field
The visual field is 180º wide, minus obstructions from facial features such as nose and cheeks.
Binocular Vision
Both eyes focus on the same center of vision. The slight difference in the information each eye receives is what provides us with 3-D depth.
The part of the eye that controls how much light enters is called the ______.
Iris.
Adaptation
The physiological process where the eye changes to adapt to different levels of illumination. Includes changes in the pupil diameter and retinal cell sensitivity.
Transmittance
The quality of a material to transmit light either specularly or diffusely. It is the ratio of transmitted light to incident light and is less than 1.0.
Transmitted Luminance
A product of the transmittance and the illuminance on the reverse side. The unit of transmitted illuminance is either candelas per square foot or footlamberts.
When light hits a surface, it can be ______, ______, or ________.
Transmitted, reflected, absorbed.
Absorption
The ratio of absorbed flux to incident flux.
Do we see with our eyes or our brain?
Our brain. The eye contains the photoreceptors that receive the light but they cannot see. Sight is done with the occipital lobe, a large area of the brain at the back of one’s head. The brain sees in 2D but uses learned cues to perceive a 3D space.
Optics
In luminaire design, optics is the science of getting a light to do what one wants by interacting the light with lenses and reflectors of the luminaire.
Fiber Optics
Fiber optics are very thin fibers of glass that can be used to transmit light over long distances.
