What is beam intensity?
How strong a fixture’s light is across its beam, from the peak on the axis to the edge where it falls away.
Beam intensity is the luminous intensity at points within a fixture’s beam, measured in candela. It is highest on the beam axis, where the peak is found, and falls as the angle moves away from it.
The beam edge is where intensity falls to a stated fraction of the peak, and the angle between the two edges is the beam spread. The fraction is set by the standard or the manufacturer, so spread values only compare when the same level is used. That is why AGL requirements are written as intensity at defined angles, not as one number, and why a fixture is checked across its beam.
Frequently Asked Questions
Q1What is beam intensity?
The luminous intensity at points within a fixture’s beam, measured in candela. It shows how strong the light is along the beam axis and at angles away from it.
Q2Where is beam intensity highest?
On the beam axis, where the peak intensity is found. It falls as the angle moves away from the axis, so a beam is described by a pattern of values, not a single number.
Q3What defines the edge of the beam?
The angle at which intensity falls to a stated fraction of the peak. The fraction comes from the standard or the manufacturer, so beam spread values can only be compared when the same level is used.
Q4Why is beam intensity given at many points?
Because it changes with direction. A fixture can meet its requirement on the axis and still fail at another angle, so the requirement and the measurement cover a set of defined angles.
Q5How is beam intensity different from luminous intensity?
Luminous intensity is the general quantity, the light sent in one direction. Beam intensity refers to those values inside the beam, which is the part of the distribution that does the work of guiding the pilot.
Q6How is beam intensity checked?
It is measured at defined angles during photometric testing and compared with the requirement for that fixture type from the standard and the manufacturer’s data.
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