Managing energy:
different approaches
A headlamp's energy source can be managed in a number of ways.
STANDARD LIGHTING
CONSTANT LIGHTING
Principle: the headlamp supplies energy "directly" to the light source
Principle: the headlamp has an integrated electronic regulation system
• Light output decreases progressively as the energy source discharges.
The headlamp light is very intense for the first minutes, and then
decreases gradually over time
• Light output is constant during a predetermined period. The duration
corresponds to true usable burn time (and does not include reserve
lighting)
• Constant lighting allows the light output measured during this period to
be specified. This is the guaranteed brightness
• The rated brightness is the maximum light output, measured when the
lamp is first turned on. This is the initial light output
Notes:
- the greater the initial brightness of a STANDARD LIGHTING headlamp,
the faster it decreases
- when the performance ratings indicate a very high brightness with a very
long burn time, one must be aware that these figures often correspond to
light output in maximum mode and to burn time in minimum mode. These
two characteristics can not be obtained simultaneously
• Most regulated headlamps move to reserve lighting mode when the
energy source is nearly depleted (up to several dozen hours for certain
products)
Notes: To obtain 100 lumens of brightness for 50 hours, for example, the
equivalent of 75 AAA batteries would be required, translating to 1.1 kg on
the head! Therefore, Petzl recommends that the user use caution when
interpreting the impressive lighting performance claims made for some
headlamps.
CONSTANT LIGHTING
Brightness
STANDARD LIGHTING
Initial light
output
Guaranteed burn time
Note:
It is not possible to directly compare the
lighting performance of CONSTANT LIGHTING
headlamps (guaranteed light output over a given
length of time) with that of STANDARD LIGHTING
headlamps (high but brief initial light output).
Guaranteed
light output
Reserve lighting
t=0
Burn time
LIGHTING