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Reviews posted after mid February 2005 will include runtime
graphs which display the output of the light over time. This
is possible thanks to our advertisers who have paid for banner
space on the front page. The revenue has allowed FlashlightReviews.com
to purchase an Extech 401036 data logging light meter. This
meter serves as a stand-alone recording device and needs no
monitoring once recording is initiated. The data is later
extracted from the meter and manipulated in a spreadsheet
program to create the plots seen in the reviews. Reviews posted
before mid February 2005 will have runtime plots added as
time permits and resources allow.
On each graph you will see the following:
A red
line which plots the output of the light over time.
A Y-axis which marks the percentage output level from the
start of recording.
An X-axis with a time scale.
Conspicuously
absent on the Y-axis is the output level of the light in Lux,
which is what the light meter actually reads. Why was this
removed? It was removed simply because it is very difficult
to align the light with the light sensor so that the distance
between the two is exactly 1 meter. The support rig I have
designed allows the light and meter to be separated by various
set distances, but fine tuning is not possible. Since the
recording distance is not 1 meter, the numbers on the runtime
plot do not match the "throw" numbers listed in the review
which are taken at 1 meter. To avoid confusion, the Lux numbers
were simply removed from the plots. The change in output over
time is the same regardless of the distance from the meter,
so the plot looks the same whether taken at 10 meters, 1 meter
or 0.25 meters.
Despite
the lack of Lux numbers, we can learn a great deal about a
light from the runtime plot. Regulated lights tend to have
either a flat or fairly flat curve which suddenly drops to
very low levels. Very well regulated lights will have a very
flat horizontal plateau followed by a sharp drop. Unregulated
lithium lights under low current loads decline for a while,
drop a fair amount, then continue on at low levels for a long
time. Unregulated lithium lights under high current loads
form a short plateau, a long sliding decline, followed by
a short bottom plateau. Unregulated alkaline lights drop rapidly
followed by a long tail. So, based upon the curve we can often
tell the battery type used and whether the light is regulated
or unregulated.
Example
of a regulated light
Example of a non-regulated Lithium powered light under low/medium
current draw
Example
of an unregulated alkaline light - note most light produced
is less than 1/2 Starting brightness
One of
the main purposes of having runtime plots in the reviews will
be to dispel the manufacturer's claims of ridiculously high
numbers of runtime hours. This problem is rampant when dealing
with LED lights. Sure you may be able to use the light to
read a newspaper in the pitch dark at 3 inches after 100 hours
of operation, but what good is it?
Packaging claims output for 72 hours.
Output drops below 50% in less than 3 hours and is
less than 1% by 9 hours.
The runtime graph exposes the marketing hype for what it
is.
I have
chosen the 50% output point as a good indicator of true battery
life. I would expect that a consumer would buy a light which
has output that matches their needs and when it drops below
50% of that output the light is no longer meeting their original
needs and the batteries will have to be replaced. The additional
10, 100, 1000 (or whatever) hours of runtime are essentially
useless for the meeting the needs of that consumer. Another
reason the 50% point of output is good to use as an indicator
of the effective life of the batteries is because this point
is often reached soon after a regulated light drops out of
regulation. For unregulated lights it marks the point when
output is in a significant decline phase and the drop in output
is very noticeable.
The graphs
will be made with the batteries included with the light (if
batteries are included). Different batteries will result in
different runtime graphs. If we wanted a greater degree of
accuracy for runtime data in general, all lights would be
tested with the same batteries, or each would be tested with
multiple brands and the data averaged. Since financial constraints
prevent this, we will have to work with the batteries provided.
If no batteries are provided, the brand of batteries used
will be randomly selected from new in-stock cells available
(aka, "whatever new batteries I have lying around..."). The
brand used will be stated in the review.
All runtime
plot analysis is completed after initial testing of the light,
beam photographs, and initial readings for Throw and Overall
Output are taken. Therefore, each set of batteries used for
the runtime plot will have about 5 minutes of total use before
the plotting is actually started. As a result, and as a result
of the differences in the runtimes resulting from different
brands of batteries, the runtime to 50% output should be considered
approximate.
The time
scale on the X-axis will likely change from graph to graph
due to space constraints. Take this into consideration when
viewing different graphs.
I sincerely
hope that including the runtime graphs is a beneficial move
for everyone who enjoys reading the content here at FlashlightReviews.com.
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