BLACK DIAMOND ZENIX HEADLAMP
FIELD REPORT
Report Date: April 13, 2004
Reviewer Information
Name: Edward Ripley-Duggan
Age: 50
Gender: Male
Height: 6' 1" (1.85 m)
Weight: 215 pounds (98 kg)
E-mail: erd@wilsey.net
Locarion: Catskills, New York State
Reviewer Background: See end of report
Product information
Manufacturer: Black Diamond
Address: Black Diamond Equipment, Ltd.
2084 East 3900 South
Salt Lake City, Utah 84124
Tel: 801-278-5533
E-Mail: climb@bdel.com
Year of Manufacture: 2004
URL:
http://www.bdel.com/
MSRP: $44.50
Testing environments and field-specific notes
The headlamp was first tested in the field on February 28, 2004 for 4 hours, at an altitude of approximately 2500 to 2000 ft (760 m) at the end of a long Catskill bushwhack. The ambient temperature, unusually mild for February, ranged from 28° F (-2° C) to 35° F (2° C). After the ascent of two mountains, the party I was leading lost daylight at the start of the long river-walk out of the wilderness area. This involved threading through brush, several crossings on ice bridges and avoidance of an area of known risk involving an undercut cliff below a steep sloping bank. Weather conditions were clear, with no mist.
The Zenix lamp, used on the HyperBright setting (a single high-intensity lensed LED—Light Emitting Diode), proved only just adequate for this fairly demanding section of off-trail navigation. The beam was fine for simply walking, just adequate for mid-range illumination of the navigational path, but unsatisfactory in (for example) discerning features on the other side of the river, this at a distance well within the working range specified by the manufacturer. The batteries used initially were those supplied with the unit, after approximately one hour of previous testing use. Measurement the day after this first field test gave a reading of about 150 lux (using the testing protocol outlined under "testing methods"). I've therefore taken this level of illumination to represent the absolute minimum light output for use for safe off-trail travel. In practice, 200 lux gives a far more comfortable safety margin.
The lamp was again tested on the Eastern Devil's Path in the Catskills at the end of a multi-peak traverse, with temperatures around freezing. This involved about one hour following a blazed trail, again on the HyperBright setting. The lamp, with new batteries at this point, proved perfectly adequate for picking up the slightly reflective blazes from a distance.
The SuperBright setting (two lower-intensity LED bulbs) was used overnight on a solo winter backpack a couple of weeks later. Temperatures were 15° F (-9° C) in the tent, about 10° F (-12° C) when outside. Camping elevation was 3500 ft (1100 m). This setting provided ample light for cooking, cleaning etc. outside the tent, and gave a pleasant level of light within the tent, sufficient for reading a map or book.
Shortly after this, based on concerns I had expressed regarding the rapid deterioration of light output at lower temperatures, Black Diamond generously provided me with a second Zenix lamp. Surprisingly, this proved on average eighty percent brighter with fresh batteries at room temperature (on the HyperBright setting) than the first example, though the SuperBright performance was equivalent. At 38° F (3° C) the differential between the light output was less, but still just over 40 percent. For purposes of comparison, this new lamp was used around an overnight campsite at 2490 ft (760 m), with temperatures from 24° (-4° C) to 40° F (4° C).
The difference in performance between the first and second headlamp on the high-beam setting was very striking. I have not been able to determine if the variation noted represents a quality-control issue or whether Black Diamond has improved the lamp performance.
General observations
A recent reading of incident reports in the Adirondack region of New York State serves to illustrate the importance of adequate lighting, especially during short-day winter ascents. A significant percentage of the mishaps involved hikers with inadequate lighting being overtaken by darkness. Certainly, a headlamp (which leaves hands free for poles, ice axe or simply balance) is preferable to a torch under these conditions. The Zenix, even with the shortcomings noted with the unit initially supplied, is adequate for all but the most exacting tasks, at least with fresh batteries.
"White" LED devices actually use a blue LED, treated in such a fashion that a certain portion of the blue light emitted is converted to yellow. The combination of blue and yellow light, while not exactly chromatically equivalent, does provide an adequate approximation to white light. I noted that the HyperBright LED was considerably whiter than the twin LEDs intended for task lighting, which have a blue cast. Though this does have some effect on accurate color perception, it does not in any consequential way affect their utility.
The headlamp generally proved stable on the head, though not as secure as some I have used, perhaps because the battery compartment is comparatively small and does not provide a terribly strong grip. In changing batteries under field conditions, I found it possible to twist the central strap by accidentally rotating the lid to the battery compartment through a full turn during reassembly, which can be rather easily done. It took me a few minutes of perplexity to work out what had happened, but my excuse is that I was tired and a bit cold! The lamp can be worn with this twist, which is easily corrected. Of greater practical import, it was quite easy to change the batteries with heavily gloved hands. The recessed mode/on-off switch is quite difficult to use in full gloves, though with great care and some practice it can be done. The gloves used had a heavy liner beneath a shell, pretty typical of what I (and most people) wear for winter mountain pursuits. A lighter fleece mitt presented no such difficulties.
My initial concerns about the brightness of the beam and, additionally, about the comparatively rapid dimming of the lamp at lower temperatures, led me to conduct some tests. The results of these are documented in the next section of the report.
Testing methods
Light output from the main HyperBright LED was measured in lux, the International Standard (SI) unit of measure for luminous flux density at a surface, using an Extech Model 40125 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. I was aware of other data pertaining to the Zenix that had also used the two-foot distance for testing, as well as the same temperature range, and I was therefore able to compare the results of the "fresh battery" test. Any major difference would indicate a problem with the testing protocol (though it would not determine which tester was at fault). In fact, the figures indeed coincided at the outset, within the tolerance of my instrumentation. The Extech has a stated accuracy of +/- 5 %.
The Zenix was outfitted with new batteries and was placed in a refrigerator, next to a calibrated digital thermometer. It was left there (turned off) for two hours to achieve thermal equilibrium. The lamp was then taken out, turned on, the refrigerator temperature was noted, and a reading in lux of the lamp brightness was taken in a darkened room. The lamp was moved until the beam was centered on the measuring element, and the highest recorded figure from the light meter was noted. This procedure generally took under a minute; so any warming of the battery compartment was of minimal concern. The lamp (now left on for the duration of the test) was then replaced in the fridge, and readings were taken by the same method at exact hourly intervals, for eight hours total, yielding nine data points. The average temperature at time of test was 38° F (3.3° C). The variation from this average was +/- 2° F (1.1° C).
An Excel spreadsheet was prepared with the results and a plot was made (with error bars of +/- 5 %), and is shown below. Not shown on this chart is one final result. At 14 hours the Zenix registered a meager 19 lux, an essentially useless level of illumination for navigation, though barely adequate for limited task lighting. The comparatively rapid drop in illumination to the 150-lux threshold was what led me to contact Black Diamond, who (as previously noted) gave me a second lamp for testing. The performance of this lamp is also shown on the chart. Unquestionably, this second lamp provides far superior performance, but (as I have no way to determine which of the lamps is anomalous) my review and remarks are based on the lamp initially supplied.
Interpretation of results
Alkaline batteries perform poorly at temperatures close to or below freezing, an issue of particular concern in a headlamp. The rate at which they exhaust is dramatically accelerated in comparison to that at milder temperatures. The light output of the headlamp on the high-beam setting is roughly proportional to the available battery power. My field-testing has demonstrated that the minimum light level for off-trail navigation, or even confident navigation on-trail (with some ability to resolve terrain details at the manufacturer's suggested 115 foot, 35 meter maximum range) is in excess of 150 lux. With the battery compartment at 38° F (3.3° C), testing shows that this level will be reached in about 4.5 hours. In addition, an almost thirty percent reduction in beam strength will be experienced within the first hour, although after that time the deterioration in beam strength is closer to ten percent per hour.
Possible solutions
Once Lithium AAA batteries come on the market (Duracell projects that these will be offered towards the end of 2004), low-temperature performance of headlamps and other hiking tools using AAA batteries will be much improved, though at a monetary cost. Lithium cells are far less sensitive to performance deterioration at low temperatures and discharge in a far more predictable and linear manner.
Until that time, there are several possible cold-weather strategies (short of carrying a lot of batteries and changing them rather frequently) to maximize the usefulness of the Zenix. First, the headlamp should be kept within a pocket against the body, as warm as possible, until needed. Second, a disposable handwarmer pad strapped to the outside of the battery case appears to be effective in keeping the temperature elevated for a considerable period. Third, the battery pack should be kept under a hat or neck gaiter, to maximize warming by body heat. Unfortunately, this is not comfortable during periods of intense physical activity unless the temperature is well below freezing. Other solutions await the ingenious.
Reviewer biography
I hike regularly year-round in the Catskills, with occasional excursions to the Adirondacks and elsewhere. A hiker since my teens, I was born and grew up in rural Hertfordshire in England, moving to the US at age 19. Given the harsh winters of the region where I make my home (and the need to keep active or perish of boredom) I make frequent ascents of local peaks on snowshoes and crampons, with an occasional foray on cross-country skis. Nothing could be further removed from the landscape of my childhood.
I enjoy walking in all its manifold forms, from a simple stroll in the woods to multi-day backpack excursions. I through-hiked the Northville-Placid trail over ten days on 2003. Though by no means an extreme ultralight enthusiast, from spring to fall my preference is to carry a packweight of 12 pounds (5.5 kg), 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.
