Luminaires - Light ControlA 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 ControlMethods of light control:

Reflection of LightSpecular ReflectionSpread ReflectionDiffuse ReflectionCompound ReflectionSelective Reflection

Reflector DesignSpherical ReflectorElliptical ReflectorParabolic ReflectorCompound Reflector

Luminaires - Light ControlMethods of light control:

Light TransmissionSpread Transmission

Diffuse Transmission

Selective Transmission

Absorption

Refraction

Concealment

Luminaires - Light ControlReflection of Light: Specular Reflection

A mirror surface. Effective in reflecting light, but creates problems with glare. Good for creating precise light control.

Angle of

Incident

Angle of

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 ControlMethods 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.

Angle of

Incident

Angle of

Reflection

Spread reflection can be seen in light reflectors. Hammered metal surfaces, etched metal surfaces, glossy paints, and brushed metals are all forms of spread reflective surfaces.

Luminaires - Light ControlMethods 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.

Angle of

Incident

Angle of

Reflection

Diffuse reflection is caused when the surface of a 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods of light control: Transmission

Materials can contain combinations of transmission properties. Colored glass can contain both selective and spread properties.

Luminaires - Light ControlMethods 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 ControlMethods 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 ControlMethods 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 ControlMethods of light control: Concealment

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.

45 degrees

Less than 30 degrees

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