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Lighting
Reference System
What
is a lighting reference system?
Black
Diamond, key headlamp suppliers and retailers came
together recently to build a single system for
measuring light output and burn times. That means
that as you try to compare the brightness and battery
life settings of headlamps of different brands
you should find the measurements calculated using
the same system, making it easier for you to cross
compare models and make the right buying decision.
The
limits: It’s impossible to find
a measurement system that captures all the important
features of light output and light duration.
The current system favors lamps that have a strong
center point of light and does not take into
account the overall shape of the light output
or the strength of the light output outside of
the center point. Therefore a lamp that projects
a very strong pinpoint of light with a very weak
surrounding beam might receive a longer, farther
distance rating than a lamp that offers a stronger
wide beam with very strong pinpoint center.
What
does it measure?
The
first step in measuring light output is determining
the minimal amount of light needed to perform an
activity. We call this minimal amount of light usablelight. Usable
light is defined as the light provided from
a full moon on a clear night. As a base reference,
this has been calculated to be 0.25 Lux (lumens
per square meter).
In
all measurements of battery life and distance,
0.25 lux from a distance of 2 meters serves as
the baseline.
The
Lighting Reference System rates headlamp performance
based on two criteria: distance of the beam and
battery life.
Distance = Distance
light can reach and still provide 0.25 lux of light
at the center point.
Battery
Life = Battery life is measured
as the amount of time the lamp will illuminate
a single axis point with 0.25 lux measured
from 2 meters distance.
Distance – How
to calculate
Distance,
measured in meters, is defined as the distance
a light can reach maintaining the output of 0.25
lux. As battery power is used, the distance the
light project at a minimum of 0.25 lux will decline
(current can be regulated to provide a unique light
projection pattern). Distance is measured at the
following time intervals:
t
= 0 h Initial brightness (to
be recorded within the first 5 minutes of turning
the lamp on)
t
= 0:30 h The average amount of use
a light 30 minutes after start-up
t = 10 h The
amount of light after a full night
of use (10 hours)
t = x h Additional points of time to measure
Distance
We
provide Distance specifications in the
following format:
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t
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Distance
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0
h
|
xx
m
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0:30
h
|
xx
m
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4
h
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xx
m
|
|
|
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10
h
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x
m
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Testing
Procedure for Distance
Five
lamps are each tested with 2 sets of batteries
of the same brand provided at retail. The average
of the 10 data points collected is what is published
on our packaging and website.
To
calculate the beam distance, measure peak intensity
at 2 meters at the optical axis or brightest point
in the beam pattern using a constant power source
where the input voltage is equal to the battery
input.
For
example: 4AA batteries = 6 volts
2
AA batteries = 3 volts
Use
the inverse proportion formula to calculate the
distance the light source will provide 0.25 lux.
To
calculate the beam distance at each of the time
periods T
EXAMPLE:
1.
Measure peak luminance of the light source at
2 meters (d =2 m).
(For
this example we assume the luminance is 200 lux)
2.
Calculate the intensity
(The intensity is: 200 lux x 2² meters = 800 candela).
3.
Calculate the square root to obtain the distance
(Working backwards: .25 lux is the square root of (800/0.25lux)=56.6 meters
Battery
Life
Battery
Life, measured in hours, is defined as the amount
of time the lamp will illuminate a single axis
point with 0.25 lux measured from 2 meters distance.
Battery life is listed in hours and rounded to
the nearest 30 minutes.
Testing
Procedure for Battery Life
Measure
light output at time t = 0 hours using a power
source of constant voltage equal to the output
of the battery system intended for the lamp. Place
lamp in a fixture that is set at 2 meters distance
from the light sensor and lower the voltage of
the power source until the light output from 2
meters is 0.25 lux. A multimeter is used to measure
the voltage going into the lamp while the lamp
is producing 0.25 lux at 2 meters.
To
test battery life, insert fresh batteries of the
same brand and type as the batteries included with
the product. Turn the lamp “on” and
start the time monitoring the time expired until
the voltage of the batteries is the same as the
voltage read when the light meter measures 0.25
lux. If batteries are not included with the product
use Energizer® or Duracell® alkaline batteries
or whatever battery is recommended on the packaging
or instructions. If the lamp has an auto-shutoff
feature manually restart the lamp within a minute
after it automatically shuts off.
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