Luminaires - Light Control
A fixture is a lighting device without lamps.
A luminaire is a light fixture with lamps installed.
Typically bare lamps are not acceptable. Bare,
exposed lamps can cause problems with glare.
Luminaires are designed to assist with light
control. Well designed light control may reduce
glare, improve aesthetics, increase visual comfort,
and allow for precise light distribution.
Luminaires - Light Control
Methods of light control:
Reflection of Light
Specular Reflection
Spread Reflection
Diffuse Reflection
Compound Reflection
Selective Reflection
Reflector Design
Spherical Reflector
Elliptical Reflector
Parabolic Reflector
Compound Reflector
Luminaires - Light Control
Methods of light control:
Light Transmission
Spread Transmission
Diffuse Transmission
Selective Transmission
Absorption
Refraction
Concealment
Luminaires - Light Control
Reflection of Light: Specular Reflection
A mirror surface. Effective in reflecting light, but creates
problems with glare. Good for creating precise light control.
Angle of
Angle of
Incident
Reflection
On a specular surface
the angle of incident
equals the angle of
reflection. Luminaires
that use specular
materials are typically
trying to precisely control
the light.
Luminaires - Light Control
Methods of light control: Spread Reflection
When light strikes a surface and the light is reflected in the
same general direction it can be classified as spread
reflection.
Spread reflection can be
Angle of
Angle of
seen in light reflectors.
Incident
Reflection
Hammered metal surfaces,
etched metal surfaces,
glossy paints, and brushed
metals are all forms of
spread reflective surfaces.
Luminaires - Light Control
Methods of light control: Diffuse Reflection
When light strikes a surface and the light is reflected all
directions the material is diffuse. These surfaces are
typically non shiny and matte.
Diffuse reflection is caused
Angle of
Angle of
when the surface of a
Incident
Reflection
material is rough and the light
is reflected in all directions.
Due to the rough surface dirt
is easily collected on the
surface of the material.
Luminaires - Light Control
Methods of light control: Compound Reflection
When light strikes a surface and the light reflects off the
material in a combination of specular, spread, and or
diffuse it can be classified as compound reflection.
Luminaires - Light Control
Methods of light control: Selective Reflection
When light strikes a surface some of the wave lengths of
energy are absorbed and some are reflected. The light
reflected from a surface will take on the color of the
material.
If the inside of a cove that is
painted green the light will
take on a green hue.
Luminaires - Light Control
Methods of light control: Spherical Reflector
When light strikes the
reflector it is reflected directly
back through the light source.
Spherical reflectors are
typically found in projectors.Ê
Luminaires - Light Control
Methods of light control: Elliptical Reflector
An ellipse is made of two focal points. In an
elliptical reflector the lamp is centered in one of
the focal points.
Luminaires - Light Control
Methods of light control: Elliptical Reflector
The light is reflected from the reflector back to the
second focal point in the ellipse. Elliptical reflectors
are used for creating spot lighting. The spots can be
narrow and focused or wide floods. Some elliptical
reflectors can be adjusted to change the focal point
length.
Luminaires - Light Control
Methods of light control: Parabolic Reflector
In a parabolic reflector
the light is reflected in
a parallel pattern.
Parabolic reflectors
and optics are found in
ambient light fixture to
help reduce glare.
Luminaires - Light Control
Methods of light control: Compound Reflector
A compound reflector
combines two reflector
forms. A combination
spherical and parabolic
reflector is often used
in cove lighting.
Luminaires - Light Control
Methods of light control: Direct Transmission
Direct transmission
occurs in clear materials
such as glass. Light
passes through the
material with little change
in direction. Some of the
light energy is absorbed
when it is transmitted
though a material.
Luminaires - Light Control
Methods of light control: Spread Transmission
Spread transmission
occurs in materials when
light has a slight
spreading effect when it
passes through a
material. Patterned and
frosted glass are
examples of spread
transmission materials.
Luminaires - Light Control
Methods of light control: Diffuse Transmission
Diffuse transmission
occurs in materials when
material has the same
brightness from all
angles. In a material with
diffuse transmission you
can not see the light
source behind the
material. Opal and milky
glass have diffuse
properties.
Luminaires - Light Control
Methods of light control: Selective Transmission
Selective transmission
occurs in materials when
some of the wave
lengths of the light are
absorbed and other
wave lengths pass
through the material.
Color glass would be an
example of selective
transmission.
Luminaires - Light Control
Methods of light control: Transmission
Materials can contain
combinations of
transmission properties.
Colored glass can
contain both selective
and spread properties.
Luminaires - Light Control
Methods of light control: Absorption
Absorption reduces the efficiency of a light
fixture, but it is effective in aiding in the
control of light and reducing glare. Many
down light fixtures are designed with black
baffles. The black absorbs the light and
reduces the glare.
Luminaires - Light Control
Methods of light control: Refraction
Refraction is the change in direction of light as it
passes between media with different densities.
Refraction is used in lenses. This technique is
common in lenses used in light fixtures.
Luminaires - Light Control
Methods of light control: Concealment
Concealment is used to hide the light
source from normal viewing angles. Coves,
louvers, and cornices are uses to obstruct
lamps from direct view.
Cove Detail
Cornice
Example
Luminaires - Light Control
Methods of light control: Concealment
Less than
30 degrees
45 degrees
Louvers with a viewing angle of 45
degrees are typically optimal for
increasing visual comfort. A louver with
less than a 30 degree viewing angle are
not effective.
Luminaires - Searching on
the Internet
LightSearch - An internet sight that links manufactures of fixtures and
lamps across the architectural lighting industry.
http://www.lightsearch.com