Book Overview
"The Science of Lighting" is a comprehensive guide that explores the fundamental principles of light, vision, and lighting technology. Written by lighting experts Prof. Wout van Bommel and Abdo Rouhana from Signify Lighting Academy, this book bridges the gap between technical lighting products and human reactions to lighting environments.
Core Philosophy: Lighting science connects technical aspects with human factors, making it relevant across diverse professions including technical, artistic, commercial, and administrative roles in the lighting industry.
Key Data Points
Key Insights Summary
Light as Electromagnetic Radiation
Light is described by both electromagnetic wave theory and quantum theory. It consists of transverse waves that travel through vacuum at approximately 300,000 km/s, with properties determined by wavelength and frequency.
Human Vision Complexity
The human eye contains over 100 million light-sensitive nerve endings (rods and cones) that enable vision across an enormous lighting-level range of more than 1 to 10 million, distinguishing up to 100,000 color shades.
Three Light Production Methods
Artificial light is produced through thermal radiators (incandescent), gas discharge radiators (fluorescent), and solid-state radiators (LEDs), each with distinct efficiency, spectrum, and application characteristics.
Photometric Quantities
Lighting engineering uses specialized units including luminous flux (lumens), luminous intensity (candela), illuminance (lux), and luminance (cd/m²) that account for both energy content and human eye sensitivity.
Non-Visual Biological Effects
Light affects circadian rhythms through specialized photoreceptor cells (ipRGCs) connected to the biological clock, influencing sleep-wake cycles, hormone production, and overall health.
Comprehensive Lighting Quality
Quality lighting installations balance lighting level, spatial distribution, directionality, and color characteristics to ensure visual performance, comfort, well-being, and environmental responsibility.
Content Overview
Book Contents
Chapter 1: Light and Radiation
Electromagnetic Wave Theory
Light is electromagnetic radiation consisting of transverse waves that travel from sources in all directions. Unlike sound waves, light waves consist of electric and magnetic field waves perpendicular to the direction of travel and can travel through vacuum.
Electromagnetic Spectrum
The electromagnetic spectrum ranges from long-wave radio transmissions (up to 2,000 meters) to cosmic rays (down to 10⁻¹⁸ meter). Visible light occupies the wavelength range between 380-780 nanometers, with different wavelengths producing different color impressions.
Quantum Theory
Max Planck's quantum theory established that electromagnetic energy is emitted in discrete portions called quanta (photons for visible light). Energy content is directly related to frequency: E = h·f = h·c/λ, explaining why shorter wavelengths have higher energy.
Chapter 2: How is Light Produced?
Thermal Radiators
Bodies emitting electromagnetic radiation due to increased temperature, such as incandescent lamps and the sun. Color temperature characterizes the perceived color, with lower temperatures (2000-3000K) appearing warmer and higher temperatures (5000K+) appearing cooler.
Gas Discharge Radiators
Light produced by sending electron streams through gases in transparent tubes. Includes low-pressure (fluorescent lamps) and high-pressure discharge lamps (HID lamps), offering higher efficiency (up to 15x incandescent) and longer lifetimes (10,000-25,000 hours).
Solid-State Radiators
LEDs produce light through electron movement across p-n junctions in semiconductor materials. Modern LEDs achieve efficiencies comparable to gas discharge lamps, with white light produced through RGB combination or phosphor conversion.
Lamp Types and Properties
Different applications require specific lamp properties including efficacy, color temperature, color rendering, lifetime, dimmability, and physical characteristics. Lamp pedigree shows relationships between thermal, gas discharge, and solid-state lighting technologies.
Chapter 3: How is Light Directed and Screened?
Reflection
Light direction control using surfaces with specific reflectance properties. Types include specular reflection (mirror-like), diffuse reflection (scattered in all directions), and mixed reflection. Total internal reflection in optical fibers enables efficient light transmission.
Absorption and Transmission
Non-reflected light is either absorbed (converted to heat) or transmitted through materials. Transmittance varies with material properties and wavelength, with colored filters selectively transmitting specific spectral components.
Refraction
Light bending when passing between media of different densities, governed by Snell's Law: sinα₁/sinα₂ = n₁/n₂. Refractive index varies with wavelength, causing chromatic dispersion in prisms and lenses.
Interference
Wave nature of light creates interference effects used in dichroic coatings, anti-reflective surfaces, and color filters. Thin-film interference separates radiation components, enabling technologies like cool-beam halogen lamps.
Chapter 4: Quantities and Units
Photometric Quantities
Specialized lighting units account for both radiation energy and human eye sensitivity (V(λ) curve). Key quantities include luminous flux (lumens), luminous intensity (candela), illuminance (lux), and luminance (cd/m²).
Practical Relationships
Fundamental relationships include inverse square law (E = I/d²), cosine law for angled surfaces, and formulas connecting illuminance with luminance for diffuse reflecting surfaces (L = ρ·E/π).
Measurement Techniques
Light meters use photocells to measure illuminance, with specialized instruments for luminous intensity (gonio-photometers), luminous flux (Ulbricht spheres), and luminance (luminance meters).
Chapter 5: Light and Vision
Visual Process and Eye Anatomy
The human eye functions similarly to a camera, with cornea, lens, iris, and retina processing visual information. Over 80% of environmental information is received through vision.
Rod and Cone Vision
Rods enable scotopic vision (low light, monochromatic, peripheral) with peak sensitivity at 507nm. Cones enable photopic vision (bright light, color, detailed) with peak sensitivity at 555nm. Mesopic vision involves both systems at intermediate lighting levels.
Eye Adjustment Mechanisms
Accommodation (focusing), adaptation (sensitivity adjustment), and convergence (binocular coordination) enable optimal vision across varying conditions and distances.
Visual Performance and Comfort
Contrast detection, visual acuity, and glare management determine visual performance. Factors include adaptation state, object size, observation time, and age-related vision changes.
Psychological and Emotional Aspects
Lighting influences emotional states, spatial perception, and atmosphere. Kruthof's curve describes preferred relationships between illuminance levels and color temperatures.
Chapter 6: Light and Color
Color Mixing
Additive color mixing (RGB light combination) produces brighter results, while subtractive mixing (paints, filters) produces darker results. Primary colors (red, green, blue) combine to form white light in additive systems.
Color Triangle and Temperature
CIE chromaticity diagram quantifies color perception using x-y coordinates. Color temperature characterizes thermal radiators, while correlated color temperature describes gas discharge and solid-state sources.
Chromatic Adaptation
The eye-brain system adapts to lighting conditions, perceiving different white balances as "white" depending on context and adaptation state.
Color Rendering
General color rendering index (Rₐ) quantifies how faithfully light sources reproduce object colors compared to reference sources. Values range from negative (poor) to 100 (excellent).
Chapter 7: Light and Health
Circadian Rhythms
Light-dark cycles regulate 24-hour biological rhythms including sleep-wake cycles, body temperature, and hormone production (cortisol, melatonin). Morning light synchronizes the internal biological clock.
Non-Visual Biological Effects
Intrinsically photosensitive retinal ganglion cells (ipRGCs) connect to the brain's biological clock (SCN), influencing physiological processes independent of visual perception.
Spectral Sensitivity Differences
Biological sensitivity peaks in the blue spectrum region (around 460-480nm), unlike visual sensitivity which peaks in green-yellow (555nm).
Lighting Therapy
Controlled lighting can treat sleep disorders, seasonal affective disorder (SAD), eating disorders, and circadian rhythm disruptions from jet lag or shift work.
Chapter 8: Lighting Quality
Lighting Level Requirements
Appropriate illuminance levels range from 0.25 lux (moonlight) to 100,000 lux (direct sunlight), with specific recommendations for different applications based on task difficulty and user age.
Spatial Distribution
Uniformity ratios, luminance distributions, and glare restrictions ensure balanced visual environments. Recommended reflectance ranges: ceiling (60-90%), walls (30-80%), working planes (20-60%), floor (10-50%).
Directionality of Light
Directional light creates modeling and shadows, diffuse light minimizes shadows, and indirect light provides soft illumination. Luminaire light distribution determines lighting effects and potential glare.
Color Considerations
Color rendering index (Rₐ) and color temperature selection depend on application requirements. Dynamic lighting can adjust both parameters to support biological needs throughout the day.
Economics and Environment
Total cost of ownership analysis balances investment costs with running costs (energy, maintenance). Lighting accounts for 19% of global electricity use, emphasizing importance of energy efficiency and environmental responsibility.
Note: This HTML provides a comprehensive overview of the book's content. The complete PDF contains detailed explanations, illustrations, formulas, and practical examples. We recommend downloading the full document for in-depth study.