Fundamentals of Light Measurement Units

Light – Visible electromagnetic Candela (cd) – SI unit of luminous

radiation; enables sight & color. intensity.

Wavelength – Distance between wave Lumen (lm) – Unit of luminous flux.

peaks; defines color.
Lux (lx) – Lumens per square meter.
Nanometer (nm) – 1 billionth of a meter;
used for measuring light wavelengths. Footcandle (fc) – Lumens per square
foot.
Angstrom (Å) – 0.1 nanometer;
extremely small wavelengths. Foot-lambert – Luminance; 1 cd/ft².

Steradian (sr) – Solid angle

measurement.
Electromagnetic Spectrum
(Ordered Shortest to Longest)
Light Behavior Laws
Gamma Rays – Shortest, highest
energy; used in medicine/science. Inverse Square Law – light intensity
decreases in proportion to the
X-rays – High energy; used in imaging.
square of the distance from the
Ultraviolet (UV) – Invisible light source.
before violet; can fade materials.
Cosine Law - illuminance on a surface is
*Visible Light – 380 nm (violet) to 700 nm (red).* proportional to the cosine of the
angle between the light source and
Infrared (IR) – Heat radiation; longer
the surface normal.
than visible light.
Law of Reflection – Angle of incidence
Microwaves – Used in communication &
= angle of reflection.
cooking.
(the angle of reflection is equal to
Radio Waves – Longest; used in
the angle of incidence, also the
broadcasting.
incident ray, the reflected ray, and
the normal to the surface all lie in
the same plane.)
Photometric Terms

Luminous Intensity – strength of light

in a focused beam; unit: Candela (cd). Light Interactions

Luminous Flux – overall brightness; Reflection – Light bounces off

unit: Lumen (lm). surface.

Illuminance – Light falling on surface; Refraction – Light bends entering a

unit: Lux or Footcandle. new medium.

Luminance – Brightness perceived Absorption – Light energy taken in by

from surface. a surface.

Brightness – Subjective perception of Transmission – Light passes through a

light intensity. material.

Diffusion – Light scatters in multiple

directions.
Diffraction – Light spreads around
obstacles.
Types of Materials (by Light
Incidence – Point where light hits a Behavior)
surface.
Transparent – Allows full light
passage (e.g., clear glass).
Reflection Types Translucent – Scatters some light
(e.g., frosted glass).
Specular Reflection – Mirror-like;
smooth surface. Opaque – Blocks all light (e.g., wood,
metal).
Diffuse Reflection – Scattered; rough
surface.

Combined Reflection – Mix of specular Light Sources

& diffuse, producing a mix of clear
and scattered reflections. Incandescent – Heat-based light (e.g.,
bulbs, candles).

Luminescent – Light without heat (e.g.,

Acoustics & Lighting Terms LEDs, glow sticks).
(Cross-Concept)

Reflection Factor – Power ratio of

reflected vs incident wave.

Reflection Coefficient (Γ) – Ratio of

reflected acoustic/light energy.

Transmission Factor (T) – Ratio of

transmitted to incident energy.

Transmission Coefficient – Ratio of

transmitted wave amplitude.

Optical Properties

Reflectance – % of light reflected by

surface.

Transmittance – % of light passed

through a material.

Luminous Transmittance – Light passing

through transparent material.

Coefficient of Transmission – Portion

of energy passed through.
Optical Concepts performed (30 inches above floor)
• Beam Spread: - Used for measuring illuminance
- Spread of an optical beam in the
atmosphere
- Affected by turbulence and Light Quality & Effects
aperture radius • Brightness Ratio:
- Reduced by increasing aperture - Impacts visual comfort and
size perception
• Beam: • Types of Glare:
- Directed propagation of light 1. Blinding
energy 2. Disability
- Has uniform amplitude in a defined 3. Discomfort
area 4. Direct
• Throw Distance: 5. Reflected
- Distance at which a beam reaches • Veiling Reflectance:
1 lux - Reflections from shiny surfaces
causing discomfort

Lighting Design Techniques

• Spacing Criteria: Lighting Techniques
- Ensures visibility, comfort, and • Direct: Focused light (e.g.,
energy efficiency in lighting downlights)
environments • Indirect: Soft, wide-area light
• Point Method: • Semi-Direct: Mostly direct, some
- Calculates illumination at a point reflected
Formula: E = (I × cos(θ)) / d² • Semi-Indirect: Mostly reflected,
Where: some direct
E = illuminance (lux) • General Diffuse: Even, non-
I = intensity (candela) directional light
θ = angle • Direct-Indirect: Balanced direct
D = distance (meters) and reflected
• Lumen Method:
- Used for average illuminance or
luminaire count Efficiency & Loss Factors
- Limitations: Not suitable for • Coefficient of Utilization (CU):
irregular or obstructed spaces Fixture efficiency
• Recoverable Losses: Cleanable or
replaceable
Room Geometry in Lighting • Non-Recoverable Losses:
• Ceiling/Room/Floor Cavity: Permanent
- Spaces around luminaires • Lumen Depreciation: Output
affecting light distribution decreases with use
• Room Cavity Ratio (RCR): • Dirt Depreciation: Dust reduces
Formula: RCR = (5 × HRC × (L + W)) / (L output
× W) or RCR = (2.5 × RCH × P) / A • Room Surface Dirt: Affects long-
• Room Cavity Height (RCH): term light reflection
Formula: RCH = LP - LCW

Natural Lighting & Daylight

Task Area Lighting • Daylighting: Controlled use of
• Work Plane: sunlight to reduce electricity use
- Surface where tasks are • Sky Component (SC): SC = (Ei / Eo) ×
100%
• Daylight Factor (DF): DF = (Ei / Eo) ×
100%
• VSC (Vertical Sky Component): Sky
visibility from window center
• Heliodon: Device to simulate sun
paths

Color & Standards (CIE)

• CIE: International Commission on
Illumination
• Color Spaces: XYZ, LAB, LUV
• CRI: Color Rendering Index
• Standard Illuminants: A
(Incandescent), D65 (Daylight), F
(Fluorescent), LED

Lighting Environments
• Clear Sky: <30% cloud cover
• Overcast Sky: Diffuse, soft lighting
• Light from behind object
• Groundlight: Lights installed in the
ground
• Artificial Sky: Simulated daylight
indoors
• Cloud Panel: Acoustic-light ceiling
system

Lighting Techniques & Tools

• Cross-Lighting:
- Opposite angle lighting to
reduce shadows
• Applications: Photography,
Theater, Landscape Design
• Benefits: Enhanced depth, reduced
shadows, texture emphasis

Organizations
• IES (Illuminating Engineering
Society): Develops lighting
standards
• IES Files: Used for digital lighting
simulation
• Standards: Roadways, workplaces,
ASHRAE/IES 90.1 energy codes
GROUP 2 - REVIEWER

LAMP - device used to produce light

INCANDESCENCE - process of producing light by heating a material until it glows

BULB - glass or plastic casing that holds the light source inside

PARTS OF BULB

FILAMENT - thin wire inside the bulb that heats up to produce light

LAMP DIAMETER - width or size of the light bulb

MAXIMUM OVERALL LENGTH - length of the bulb including it's base

LIGHT CENTER LENGTH - distance from the bottom of the bulb to the center of the light
source(filament)

EXTENDED SERVICE LAMP - type of bulb designed to last longer than regular lamps

EFFICACY - measures how efficiently a light source produces light

RATED LIFE - average number of hours expected to operate before failing

TYPES OF INCANDESCENT LAMP

THREE WAY LAMP - a lamp with three brightness levels

TUNGSTEN LAMP - lamp with tungsten filament

TUNGSTEN-HALOGEN LAMP - tungsten lamp that contains halogen gas

IR LAMP - emits infrared light for heating or therapeutic applications

LAMP BASE - part of the lamp that connects to the socket and provide electrical contact

LAMP HOLDER - lamp socket, it is the fixture into which the lamp base fits

TYPES OF BULBS

A BULB - standard bulb

B BULB - rounded or blunt tip

C BULB - cone shape

CA BULB - c bulb with a bent flame like tip

R BULB - reflective coating inside for directed light

PAR BULB - weather resistant option

ER BULB - designed to focus light forward, more concentrated

A/SB BULB - smaller version of a bulb

G BULB - round globe shape

PS BULB - bulb with longer neck

S BULB - small, used in signs, indicators, decorative

TB BULB - straight, cylindrical shape

MR BULB - compact, with focused beams

BT BULB - tubular shape with rounded ends

E BULB - elliptical shape

BALLAST - regulates the current to a lamp and provides sufficient voltage to start it

STARTER - device used in fluorescent lighting system to help initiate lamp operation

FLOURESCENCE - process where something absorbs light or energy and re emit it to glow

FLOURESCENT LAMP - tube shaped light

T BULB - modern tube shaped led light that replaces traditional fluorescent tubes

CIRCLINE LAM - round shape fluorescent tube often used in ceiling fixtures

U-BENT LAMP - fluorescent tube bent into u shape

COMPACT FLOURESCENT LAMP - small spiral shaped fluorescent kano that fits regular bulb
sockets

MINIATURE FLOURESCENT - tiny version of fluorescent light

NEON LAMP - glass tube filled with neon gas

COLD CATHODE LAMP - similar to neon lamp but smaller and dimmer

PHOSPOR - powdery material inside fluorescent bulbs

TRIPHOSPOR - blend of three phosphor materials that improves color quality etc

DISCHARGE LAMP - produces light by generating arch through a gas filled tube

PRE HEAT LAMP - fluorescent lamp designed to be used with a starting switch THAT BRIEFLY
HEATS THE LAMP'S ELECTRODES BEFORE THE LAMP CAN START, ALLOWING THE GAS INSIDE TO
CONDUCT ELECTRICITY AND PRODUCE LIGHT.

RAPID START LAMP - fluorescent lamp designed to ignite quickly without traditional starter
switch

INSTANT START LAMP - lighting system that utilizes electronic ballasts to initiate illumination

HIGH OUTPUT LAMP - light source designed to produce a significantly greater amount of
luminous flux compared to standard lamps

VERY HIGH OUTPUT LAMP - produce an exceptionally large amount of luminous flux

HIGH INTENSITY DISCHARGE LAMP - type of electric gas discharge lamp that generates light by
creating an electric arc between tungsten electrodes within gas filled tube

MERCURY LAMP - electric light that uses mercury vapor to produce light

SODIUM LAMP - gas discharge lamp that uses sodium to produce light

LOW PRESSURE SODIUM LAMP - gas discharge lamp that emits monochromatic yellow light by
passing an electric current through sodium vapor at low pressure

HIGH PRESSURE SODIUM LAMP - gas discharge lamp that produces light by passing through
sodium vapor at high pressure

METAL HALIDE LAMP - type of high intensity discharge lamp that produces light by passing an
electric current through a gas mixture

SOLAR LAMP - lighting device powered by solar energy, typically using PV cells to convert
sunlight into electricity

LIGHT EMITTING DIODE - is a semiconductor device that emits light when an electric current
passes through it
GROUP 3 ACOUSTIC AND LIGHTING SYSTEM
 COLOR TEMPERATURE -  RIDGE BAFFLE- A ridge baffle
Describes light appearance, improves attic ventilation by
measured in Kelvin (K). Range directing airflow while
Typically between 2,000K and blocking debris, rain, and
6,500K for pests, enhancing roof
residential/commercial efficiency and longevity.
lighting.
 SPECTRAL DISTRIBUTION -  PRISMATIC LENSES -
Describes optical radiation Prismatic lenses correct
from a light source. Expressed double vision and binocular
in radiometric terms like vision issues by bending light
Spectral Power Distribution to align images.
(SPD).
 COLOR RENDERING INDEX -  LOUVERS -A louver is an
Measures how accurately a architectural feature with
light source displays colors. 0 angled slats that regulate
to 100, with higher values airflow and light while blocking
indicating better color rain, sunlight, and noise.
accuracy.
 LUMINAIRE - A luminaire is an  BAFFLE - baffle is a structure
architectural element that that controls the flow of fluids,
enhances design through light, sound, or air.
lighting.
TYPES OF LUMINAIRES  SHIELDING ANGLE - It is the
angle measured from the
 Indoor Luminaires: Used in horizontal plane at which
homes and offices direct glare from a light source
 Outdoor Luminaires: Designed is blocked by a fixture.
for exterior use
 REFLECTOR - Direct light  EGGCRATE - It is a grid-like
through reflection and structure used in lighting
refraction fixtures to control light
distribution and reduce glare.

 FRESNEL LENS - Fresnel lens,  PARABOLIC REFLECTOR - It is

developed by Augustin Fresnel a reflective surface shaped like
for lighthouses, uses a paraboloid that directs light
concentric stepped rings to into a parallel beam.
efficiently focus light.
 LENS - optical device that  COLLIMATE - It is the process
focuses or disperses light of making light rays parallel to
through refraction, made from reduce divergence and
glass or plastic. improve beam focus
 LENSES CALCULATION  ELLIPTICAL REFLECTOR - It is
a reflector with an elliptical
shape that focuses light from
one focal point to another.
GROUP 3 ACOUSTIC AND LIGHTING SYSTEM
 DIFFUSER - It is a material or  RECESSED LIGHT - fixture
device that scatters light to installed into a ceiling or wall,
reduce harshness and create creating a sleek, low-profile
uniform illumination. appearance
 CANDLE POWER  RECESSED FLUORESCENT
DISTRIBUTOR - It is a LIGHTING - recessed fixture
graphical representation of that uses fluorescent tubes or
how light intensity is bulbs
distributed in different
directions from a source.

 CURVE - graphical  RECESSED CAN - recessed

representation of the lighting fixture with a
distribution, intensity, or cylindrical housing that is
behavior of light emitted from typically installed into a ceiling
a source.
 SOLUX LINE - It is a high-  WALL WASH - lighting
performance lighting system technique or effect where light
that closely replicates natural is distributed evenly across
daylight. the entire surface of a wall.
 LUMINAIRE EFFICIENCY - ratio  UNDER-CABINET LIGHTING -
of the luminous flux (light added under a cabinet, shelf,
output) emitted by a luminaire or similar surface to produce
to the total luminous flux localized lighting on a work
produced by the light source. surface.
 POINT SOURCE - small light  WALL SCONCE - mounted on a
source that emits light in all wall. sconces can be used to
directions from a single point. provide general lighting, task
lighting, or accent lighting.
LIGHT FIXTURE TYPE  TASK LIGHTING - illuminate a
specific area or task
 RECESSED COVE FIXTURE -
installed into a ceiling or wall
cove, which is a specially
designed recessed area.
 INDIRECT LIGHTING - FORM  WALL WASHER - specifically
OF AMBIENT LIGHTING. IT designed to create a wall wash
MINIMIZES SHADOWS AND effect.
REFLECTED GLARE.

 DIRECT- INDIRECT LIGHTING - lighting  FLOOD LIGHT - is a broad-beamed, high-

system that combines both direct and intensity artificial light. it can provide
indirect light sources. functional area lighting for travel-ways,
parking, entrances, work areas
 DECORATIVE LIGHT - decorative lighting  DOWNLIGHTS - directional lighting
is used purely for aesthetic purposes fixtures that produce a wider, more
diffused light.
GROUP 3 ACOUSTIC AND LIGHTING SYSTEM
 SPOTLIGHT - way to layer  VALANCE lighting - installed
lighting in a space or to behind a horizontal shield or
provide task lighting. valance, mounted above
windows or along walls, to
direct light upward and
downward.
 SPILL - unwanted light that SURFACE MOUNTED
falls outside the intended area
of illumination, potentially  CEILING-MOUNTED LIGHTING
causing glare, discomfort, and FIXTURES - directly attached
reduced visibility. to the ceiling surface rather
than being recessed or
suspended.
DESIGN AND DISPLAY LIGHTS  WALL-MOUNTED LIGHTING
FIXTURES - attached directly
 TRACK LIGHTING - light to a wall rather than the ceiling
fixtures are attached anywhere or floor.
on a continuous track device
which contains electrical
conductors
 LIGHTSTRIP - row of electric INDOOR LIGHTING
lights, often LED lights
 PENDANT
is a single light fixture that hangs from
the ceiling.

 SCONCE - wall-mounted light  REEL/ DROPLIGT

fixture. It is typically attached an electric light suspended by a
to a wall rather than hanging cord or on a portable extension
from the ceiling or standing on
the floor.
 BRIDGE LAMP - floor lamp  LUMINOUS CELING
characterized by a horizontal is an architectural element that
arm (the "bridge") that extends integrates lighting and design in a
from the upright column harmonious manner.

 GOOSENECK LAMP - flexible lamp with  -RECESSED

an adjustable, curved neck that allows is a type of lighting that is installed within a
you to direct light precisely where you ceiling or wall.
need it
 TORCHIERE - tall, upright base and a  EXPOSED CANISTER
shade that directs light upward, towards is an architectural element that integrates lighting
the ceiling and design in a harmonious manner.
 CHANDELIER - decorative ceiling-
mounted light fixture
BUILT-IN TYPE  -EYEBALL
 COVE lighting - installed in a recessed is a type of lighting that is installed within a
area, usually along the perimeter of a ceiling or wall.
ceiling or high on walls
 CORNICE LIGHTING - mounted behind a  TROFFER - is a rectangular-shaped light fixture.
horizontal ledge or molding near the ’trough” coffer” referring to its recessed
ceiling, directing light downward or design.
upward.
GROUP 3 ACOUSTIC AND LIGHTING SYSTEM
OUTDOOR LIGHTING  SUBMERGED POOL- light
requires submersion to
 LANTERN TYPE - type of prevent overheating, and if
portable light source operated without water
TYPES OF LANTERN LIGHTS covering the lens, the lens will
shatter in under a minute.
 OIL OR CANDLE LANTERNS:  EMERGENCY LIGHT - battery-
- Feature glass panels to protect from backed lighting device that
wind and provide a warm, flickering automatically switches on
glow during power outages.

 GAS LANTERNS:
- Use fuels such as propane or butane.

BATTERY-powered Lanterns:
-Typically use LED bulbs and are safe,
portable, and increasingly popular for
outdoor use.

 LED LANTERNS:
use energy-efficient light-emitting diodes
(LEDs) to produce bright and long-
lasting illumination

 Solar Lanterns:
-Powered by sunlight, they're eco-
friendly and perfect for garden
decoration or areas with ample sunlight.

STREET LIGHTING

 PHOTOCELL - automatically turn

an LED light on or off based on
the amount of ambient light
available.
 BOLLARDS - typically installed
on the ground to illuminate
pathways, walkways, driveways,
gardens, and other outdoor areas.
 SPREAD TYPE - outdoor fixture
designed to cast a wide, low-
intensity light over a large area,
 GROUND TYPE LIGHT - installed
below ground
 STEP LIGHT - wall-mounted
lighting fixtures that provide safe
and effective illumination for
steps, staircases, and pedestrian
pathways.
GROUP 3 ACOUSTIC AND LIGHTING SYSTEM