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Princeton Tec EOS FR-TED

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  • edwardripleyduggan
    The following FR is posted on the TEST page for your reading pleasure (?) . I aware of the date discrepancy and will correct it on the final edit. Yahooisms
    Message 1 of 1 , Feb 22, 2005
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      The following FR is posted on the TEST page for your reading pleasure
      (?) <g>. I aware of the date discrepancy and will correct it on the
      final edit. Yahooisms &c.


      Field Report

      Report Date: March 1, 2005

      My initial report may be viewed here

      Reviewer Information

      * Name: Edward Ripley-Duggan
      * Age: 51
      * Gender: Male
      * Height: 6' 1" (1.85 m)
      * Weight: 215 pounds (98 kg)
      * erd@...
      * Catskills, New York State

      Reviewer Background

      I enjoy walking in all its manifold forms, from a simple stroll in
      the woods to multi-day backpack excursions. Though by no means an
      extreme ultra-light enthusiast, from spring to fall my preference is
      to carry a pack weight of 12 lb, 5.5 kg (i.e. before food and water),
      more or less. In recent years, I've rapidly moved to a philosophy of
      "lighter is better," within the constraints of budget and common sense.

      Product information in brief

      * Manufacturer: Princeton Tec
      * URL: http://www.ptsportlights.com/
      * Product: EOS Headlamp
      * Year of manufacture: 2004
      * MSRP: US $38.99 (from press release)
      * Batteries: 3 AAA
      * Manufacturer's stated weight: 3.7 oz (105 g) with standard
      AAA batteries
      * Measured weight (digital P.O. scale): 3.7 oz (105 g) with
      standard AAA batteries
      * L.E.D: 1 watt Luxeon with Princeton Tec designed lens/collimator
      * Light settings: four modes, three standard at varying levels
      of intensity, one flashing
      * Method of control: "active current control circuit"—from the
      package enclosure
      * Battery life (based on use of alkaline cells, taken from
      corporate press release):
      * High output mode–2 hours of constant brightness / 6.5 hours
      of run time
      * Medium output mode–9.5 hours of constant brightness / 12.5
      of run time
      * Low output mode–28 hours of constant brightness / 36+ of run
      * Waterproofing: "1 m waterproof" according to package (no
      standard cited)

      Field and Test Information

      For this field report, the Princeton Tec EOS headlamp was used
      extensively for "day" hikes (ending well after dark) and backpacking
      trips in the Catskill and Adirondack Mountains of New York State, at
      elevations to 4500 ft (1370 m). Much of the hiking involved off-trail
      excursions and included a number of the more difficult Catskill peaks.
      For reasons of winter safety, minimum pack load was 15 lbs (5.4 kg) or
      so for day hikes and up to 28 lbs (11.3 kg) for backpacks.

      The lowest temperatures experienced during the testing period were
      at elevation, at approximately -10 F (-23 C). The winter (and the
      testing period) began with very mild conditions, but intensified in
      mid-January with a period of intense cold and deep, dry snow. This was
      followed in early February by a period of remarkable warmth, with
      temperatures at elevation of close to 45 F (7 C). One could fairly
      characterize the weather for the Field Test period as bizarre.

      Product Use and Performance

      Some general observations

      A headlamp is a critical part of the basic equipment of the
      serious hiker and backpacker. I have led too many hikes during which
      someone tried to illuminate their way along an icy path holding a
      torch, usually with the predictable result of a slip or fall, with the
      dropped torch skittering downhill (this actually happened on a hike I
      led during the Field Test period). For safety, a good powerful
      headlamp that leaves the hands free for balance, self-arrest or other
      tasks is far and away the best tool.

      L.E.D. (Light-Emitting Diode) headlamps now have a huge advantage
      over those with bulbs, in that they make a far more efficient use of
      battery power. This in turns conserves weight, as fewer batteries are
      needed. Within the past year I have seen the technology come a long
      way. Last year's L.E.D. units produced adequate light, but that tended
      to be somewhat bluish in tint. This year, L.E.D. "bulbs," such as the
      Luxeon used in the EOS, are twice as bright and produce light with
      much less tint. "White" L.E.D. devices actually use a blue L.E.D.,
      surrounded by a plastic that contains materials that absorb and
      re-emit the light in such a fashion that a certain portion is
      converted to other colors of the spectrum. While the result is not
      exactly chromatically equivalent to white, they are now probably
      closer than many torch bulbs. While tint is not a critical issue, it
      does have bearing on such tasks as map-reading.

      How bright is "bright?"

      The critical part of testing a headlamp is how it performs in the
      field. However, as headlamp technology becomes increasingly
      sophisticated, some other measures of performance are useful in
      addition (not least because the eye is rather poor at determining
      relative brightness, etc.). I had previously developed a methodology
      for testing light output at various temperatures during another
      headlamp test. I have applied the same methods here

      Light output from the EOS was measured in lux, the International
      Standard (SI) unit of measure for luminous flux density at a surface,
      using an inexpensive digital light meter. A distance of two feet
      between the front of the lamp housing and the light meter's sensor was
      chosen for the test. This enabled the brightest region of the beam to
      coincide with the light sensor's dome. The measuring unit has a stated
      accuracy of +/-5%. A refrigerator and freezer provided the constant
      cold temperatures required.

      As a key aspect of the EOS is the circuitry designed to control
      the voltage supply to the diode, and hence maintain its brightness as
      a constant level, my tests involved charting how well this technology
      worked at the available light settings (excluding the flash setting).
      The 150 lux level shown on the charts below is equivalent to an
      intensity that I had (on a previous test) determined to be barely
      adequate for trail walking, allowing blazes to be seen but at no great
      distance. I have taken it as the minimum useful level of illumination.
      The following chart shows the output of the EOS over time at the three
      brightness settings, as an indication of the time one can expect the
      headlamp to provide useful light. The temperatures noted are the
      ambient air temperature; the lamp itself may be slightly warmed due to
      heating effects by the diode (some heat is generated, as well as light).

      room temp

      On the maximum brightness setting, when at room temperature, the
      EOS's circuitry keeps the light at constant brightness for
      approximately two hours (allowing for error, shown by the +/-5%
      vertical error bars). There is usable light for approximately eight
      hours. The two-hour period is in line with the manufacturer's claimed
      time. At the middle brightness setting (adequate, as I have noted in
      the field, for most things except serious bushwhacking), the light
      level remains constant for ten hours, before dropping off, though at
      least two hours of usable light remain (time constraints prevented me
      from depleting the output to the 150 lux level). This is also in line
      with the manufacturer's specs. At the lowest setting, enough light for
      careful trail walking over moderate terrain (and basic camp tasks) was
      generated at an almost invariable output for at least twelve hours,
      and I have little doubt that the manufacturer's claim of 28 hours of
      constant illumination at this level is accurate. Things get more
      interesting when one goes to lower temperatures.

      Freezing temps

      The pattern shown on this chart is typical of low-temperature lamp
      performance. At the maximum brightness setting at 40 F, 12 C, only one
      hour of constant brightness was produced. Usable light was produced
      for slightly in excess of six hours. At 10 F, 4 C the voltage
      correction circuitry could not keep pace with the rapid battery drain
      at all (and the initial brightness was much reduced). The light output
      of the lamp was depleted after a mere four hours. This is not a
      weakness of the headlamp, it should be noted, but of alkaline
      batteries. The chemical reaction that is responsible for creating
      electrical current is highly dependent upon the temperature of the
      battery. Clearly, if one is going to use the lamp in cold weather with
      alkaline cells, one must use the lower brightness settings and
      conserve use as much as possible.

      The solution? Lithium AAA batteries are rather expensive but I
      have been using them with this lamp in these winter months, and with
      them the performance of the lamp at low temperature is roughly
      comparable to that with alkaline cells at room temperature (see plot
      above). For winter hiking and backpacking the extra cost is money well
      spent. In addition, they are slightly lighter! However, it should be
      noted that, once they start to become depleted, performance drops far
      faster than with an alkaline cell; they discharge in a very different
      manner. Still, I was provided with full-intensity light for well over
      three hours (I tested quickly at the 3.5 hour mark, and was still
      obtaining full output).

      Out of the "lab" and on the trail!

      Eos was the Greek goddess of dawn, and while the Princeton Tec EOS
      headlamp can't rival the rising sun, it is certainly bright! On one
      hike during the Field Test period, I needed to illuminate a rugged
      snowy trail for two members of my group. This the EOS was able to do
      very capably on maximum output. The only disadvantage (true with any
      headlamp, especially so with L.E.D.s) is that anyone turning to look
      in my direction risked being painfully dazzled

      The distance at which illumination is effective is something
      that's difficult to evaluate absolutely (and which is, in any case,
      dependent on atmospheric conditions) so I am not going to attempt to
      assess the utility of the lamp in terms of how distant an object could
      be illuminated, but rather its overall utility at the various
      brightness settings. The full-power setting proved bright enough for
      just about any activity, on or off trail. It was adequate for
      bushwhacking over rough terrain, if correctly angles, showing up any
      sudden ledges well ahead of time, and with enough power that one could
      scan them to find the best point of ascent or descent. On this
      setting, if I blundered off a winding trail, as I did at one point,
      sweeping the surrounding woods was sufficient to spot a missing blaze.
      It's a comfortable feeling to have this sort of lighting power at a
      finger's touch. It proved adequate for some moderately serious
      backcountry cross-country skiing, as well as hiking.

      The middle brightness setting was adequate for some use off-trail
      on less demanding sections, and was sufficient for any trail I
      encountered. Fairly distant blazes (in this area, plastic disks)
      showed up well. The minimum setting is more than adequate for general
      camp use, and good for reading. Additionally, it's possible to walk on
      trail quite comfortably even at this level, with a little care. I
      tested the flashing mode. It flashes at maximum brightness; however,
      the beam, because it is focussed, is rather directional. Placed on top
      of a tent, it made the campsite obvious without wasting battery power,
      but in my opinion this mode should be used only as an adjunct method
      of attracting attention in an emergency.

      The manner in which the beam is focused by the collimator is
      worthy of mention. A high percentage of the light output is
      concentrated at the center of the beam; which is really where it is
      wanted. Sufficient light is dispersed to the sides to allow for some
      degree of illumination of the periphery, and this is useful. Also, as
      mentioned previously, the quality of the light emitted by the diode is
      very good. Though it tends slightly to the blue end of the spectrum
      (as an incandescent bulb tends to the red) the light is really a
      better approximation of white than I have generally encountered in
      headlamps of any kind. I have noted very little distortion of color
      values, which I find impressive.

      Other practical notes

      The headband is very easily adjusted, and provides a tight, stable
      fit, even over a winter hat (the hood of my jacket, or my Gore
      Windstopper bonnet). On bushwhacks (where it is very easy to have a
      headlamp dislodged by a branch) the lamp stayed stably on my head.
      While I tend to keep the band fairly tight, I find the lamp perfectly
      comfortable to wear for periods of several hours at a time. I tried
      setting the band to the head of one of my daughters; it is easily
      adjusts to any head size. It even fits a plastic helmet reasonably firmly.

      Changing the batteries is straightforward; using the thumbscrew at
      the rear of the lamp housing accesses the battery compartment. This
      may be firmly tightened (if preferred) by using the buckle on the
      headband, which fits into the slot on the screw. The lamp swivels
      through almost ninety degrees, from the straight-ahead position to a
      point where it is pointed down at the ground. There is a ratchet
      mechanism (not externally visible or accessible) that allows the angle
      to be changed in increments of about twelve degrees. It's very easy to
      select a position that illuminates the terrain ahead to the necessary
      extent, as I found when skiing with the lamp on. Because of the
      ratchet the lamp, once correctly angled, tends to stay locked in
      position. One minor cavil I have with the unit (as with many headlamp
      designs) is that it does not rotate up beyond the horizontal.

      As this Field Test was conducted over winter (admittedly a rather
      eccentric one, with periods of unseasonable warmth in January and
      February) I have not yet been able to test the lamp in rain. The
      waterproofing of the battery compartment (and the circuitry) is
      effected by means of a rubber gasket that sits in a groove molded in
      the lid. One point of minor concern is that (in my lamp at least) this
      gasket is a poor fit, and is loosely seated. It bulges out of its
      track slightly. While I do not think this will substantially diminish
      water resistance, I feel this worthy of note and I will be watching
      this carefully. I'm concerned that the gasket may potentially become
      completely unseated and even dropped in the process of changing
      batteries. It would be virtually impossible to remount with gloved
      hands (and easily lost against a background of forest duff or similar).

      While on the topic of gloves, I have tried operating the switch
      using a light fleece glove with a silk liner, with a heavy glove with
      an insulated liner, and in mountaineering mitts. Wearing the first
      two, switching the lamp on proved fairly easy, although slightly
      harder with the insulated gloves, naturally. Predictably, it proved a
      more awkward task wearing mitts, but it was still possible to turn the
      lamp on and off and alter the brightness mode. Changing batteries
      wearing the mitts was not really feasible, but was simple enough
      wearing gloves.

      Despite heavy use over the Field Report period, the lamp still
      looks pretty much as new. It has been dropped a couple of times
      (though not terribly hard) but doesn't seem unduly sensitive to shock.



      * Bright, controllable illumination at a low weight.
      * Comfortable and easy to adjust.
      * Excellent quality of light, with minimal color distortion.


      * Gasket that can easily become displaced or detached.
      * Lamp does not rotate up beyond horizontal.

      Future Testing Strategy

      In my further testing over the next four months, I will examine
      the following aspects.

      1. How waterproof is the lamp in heavy rain?

      2. Does the ratchet mechanism hold up to wear (there is no method
      of externally tightening this if the lamp becomes loose).

      3. Does the lamp continue to be durable overall?

      Most of the points in my initial testing strategy have been
      addressed in this report, however I'm sure there will be plenty of
      observations to be made for the Long Term report as I refine my
      knowledge of this lamp.

      I thank BackpackGearTest and Princeton Tec for permitting me to
      participate in this extremely interesting and enjoyable test.
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