chapter_05_06_07.pdf

Summary of Last Week Keys To Understanding Lighting Placement: 1. Human Adaptation to Light Variances 2. Brightness/Contrast in a Space 3. Phototropism 4. Vertical Vision: Lighting design becomes a study of contrast and placement rather than a the application of even light levels throughout a space...

Summary of Last Week Keys To Understanding Lighting Placement: 1. Human Adaptation to Light Variances 2. Brightness/Contrast in a Space 3. Phototropism 4. Vertical Vision: Lighting design becomes a study of contrast and placement rather than a the application of even light levels throughout a space. Layers of Lighting Design 1. Chorography / Destinations 2. Ambience / Mood Lighting -- Using Intensity, Color and Texture 3. Accent Lighting for Objects 4. Architectural Lighting 5. Task Lighting A small quantity of light in the right place is much more effective than any quantity of light in the wrong place. CHAPTER 5 The Basic Properties of Light Light is a member of a large family of phenomena called electromagnetic radiation (EMR) EMR is raw energy Heat, light, x-rays, microwaves, U.V. are all examples of EMR (radiation) EMR has no mass, no taste, no color All EMR radiation travels at the same speed: “the speed of light” EMR varies only in wavelength Wavelength is measured in Nano-meters We can symbolize EMR as tiny squiggly lines vibrating through space. CHAPTER 5 The Basic Properties of Light the only difference from one form of radiation to the next is… WAVELENGTH Our eyes can detect only a small portion of the spectrum: so we call this portion the visible spectrum or light The visible spectrum includes radiation from about 380 Nano- meters (violet) to 770 nano- meters (red) in wavelength CHAPTER 5 The Basic Properties of Light CHAPTER 5 The Basic Properties of Light SO… where does radiation come from, and why do we detect only a small portion of it? The SUN has historically been our primary source of radiation The sun emits almost every wavelength of EMR. We would call this a very complete spectrum Almost all of the sunʼs radiation is blocked by our atmosphere What types leak through and make it to the earths surface? The visible spectrum, some IR and some UV CHAPTER 5 The Basic Properties of Light An Introduction to basic lighting terms We quantify light as “lumens” “pieces” of light Lumens of light striking a surface = Illuminance Expressed in Foot-candles Lumens of light leaving a surface generically = Exitance Exitance is simply light leaving, with no indication of direction Lumens of light leaving a surface in a specific direction in a specific density Luminance is light leaving in a specific density as viewed from a specific vantage point Luminance is most closely related to the assessment of “brightness” Basic light interactions are always about “Lumens” of light interacting indifferent ways. CHAPTER 5 The Basic Properties of Light CHAPTER 6 Fundamentals of Vision: The Eye The mechanisms we use focus at different distances adjust for dark or bright situations Diagram the human eye Cornea: clear transmitting / refracting / protecting device Iris / pupil: some of our dark/light adaptation (dilate) Crystalline lens Flexible to change shape to refract differently to accommodate (focus) The retina: home to all of our photoreceptors (light detectors) Described as three parts: periphery, macula, fovea Can be permanently damaged CHAPTER 6 Fundamentals of Vision: The Eye Cones Populate the macula and fovea Active in high light levels (called Photopic vision) Responsible for color vision (if you perceive color, you are using cones) RHO “R” cones: sensitive to “red” light (580 nm). Contain erythrolab GAMMA “G” cones: sensitive to “green” light (540 nm). Contain chlorolab BETA “B” cones: sensitive to “blue” light (450 nm). Contain cyanolab Rods Populate the periphery of the eye Active in low light situations (called Scotopic vision - monochromatic) Very sensitive to change and motion CHAPTER 7 Color Science and Light Sources RGB Light / Additive Color For human vision performance and revealing the world around us we are usually concerned with “white” light BUT… white is a subjective experience (like all “color”) and our definition is constantly changing…. So we break it down in to two issues: COMPLETENESS OF SPECTRUM & BALANCE OF SPECTRUM CHAPTER 7 Color Science and Light Sources Completeness of spectrum / CRI We measure the complexity / completeness of a light source. We call this the COLOR RENDERING INDEX or CRI It is a numeric value ranging from 0-100 (the higher the better) Examples of CRI in lighting: Daylight: 100 Incandescent light: 100 Fluorescent: 75 - 95 Metal halide: 75-90 High pressure sodium: 25 Low pressure sodium: 25 CHAPTER 7 Color Science and Light Sources Balance of spectrum / Color temperature If a light source gives of more of one wavelength than another, than our brains translation of the light is a slight color variance We have devised a numeric description of the color produced by the imbalance called CORELATED COLOR TEMPERATURE Expressed as a temperature in degrees Kelvin K or “Kelvins” Extracted from the behavior of black metals as they are heated up: red to orange to yellow to blue etc. This behavior follows a predictable path where green would appear we get a very pale “neutral” We use it most to help describe fluorescent sources.