Lighting Engineers - Optical Data
Design the most efficient and cost effective fixtures using the world's
leading reflective surfaces with the optical data at your fingertips.
Available exclusively in Canada through Anomet, Alanod's reflective surfaces are measured and developed to meet certain photometric values, allowing for the best possible engineered lighting systems.
Click here to visit Alanod's website for additional information
Photometry
Photometry
is the science of measurement of light, in terms of its perceived brightness
to the human eye. The human eye is not equally sensitive to all wavelengths
of light. Photometry attempts to account for this by weighting the measured
power at each wavelength with a factor that represents how sensitive the eye
is at that wavelength. The standardized model of the eye's response to light
as a function of wavelength is given by the luminosity function.
Note that the eye has different responses as a function of wavelength when it is adapted to light conditions (photopic vision) and dark conditions (scotopic vision). Photometry is based on the eye's photopic response, and so photometric measurements will not accurately indicate the perceived brightness of sources in dim lighting conditions.
Photometric Quantities.
Many different units of measure are used for photometric measurements. People
sometimes ask why there need to be so many different units, or ask for conversions
between units that can't be converted (lumens and candelas, for example).
We are familiar with the idea that the adjective "heavy" can refer
to weight or density, which are fundamentally different things. Similarly,
the adjective "bright" can refer to a lamp which delivers a high
luminous flux (measured in lumens), or to a lamp which concentrates the luminous
flux it has into a very narrow beam (candelas). Because of the ways in which
light can propagate through three-dimensional space, spread out, become concentrated,
reflect off shiny or matte surfaces, and because light consists of many different
wavelengths, the number of fundamentally different kinds of light measurement
that can be made is large, and so are the numbers of quantities and units
that represent them.