From: Pawel Danielewicz Subject: [BC] Hella Micro-FF vs Bisy Date: Wed, 05 Dec 2001 14:52:04 -0500 Message-ID: <0.700001764.627908783-951758591-1007582901@topica.com> I finally got my long-awaited Hella Micro-FF dynamo lamp and had a chance to compare it to the Bisy lamp. The Hella lamp is quite small, possibly comparable in size to the active part of the Lumotec. Its diameter of 44mm is just a bit larger than half the diameter of Bisy w/o the reflecting flange. The front plastic is clear. All focusing is done by the lamp reflector. By contrast, in the Bisy, a nontrivial shape of the beam is evidently generated by the Fresnels in the front plastic. The Hella lamp generally requires a dedicated mounting bracket for a specific mounting location. Though I had no problem mounting the lamp using a standard bracket above the front wheel, I would generally suggest to get the dedicated one that would fit features of the lamp mount. In comparisons, I powered the lamps with a 6V battery and with a dynamo. When directed at a wall, the Bisy illuminates primarily a trapezoidal area, taller than wide, with a brighter smudge on top. The Hella produces a narrow horizontal smudge, wider than the Bisy's top, and a shorter smudge underneath. In my Hella, the short smudge extended more to the right than to the left. The edges of the Hella's central pattern appeared more erratic than the Bisy's (spread-out small pieces of cotton). When powered by a dynamo, the Hella's pattern was generally dimmer than the Bisy's, with no location in the Hella's pattern brighter than the Bisy's top smudge. When powered by the battery, the smudge of the Hella was just as bright as the top smudge of Bisy, despite the much larger area illuminated in a useful manner by the Bisy. The Hella's pattern is surprisingly uniformly dim farther out from the central smudges. The pattern ends with a thin circle, to one's sides and ground, stemming from the edges of the front plastic. The Bisy's edges also produce some pattern and there is some erratic illumination in-between the central region and the edge. In riding, I found it difficult to properly aim the Hella. The Bisy allows for a simultaneous illumination of close and farther out distances due to the vertically elongated rectangular shape of its beam. With the Hella, you generally need to give up on the short or far distances or both. I aimed eventually the lamp at some intermediate distance with the lamp producing a nebulous patch on the ground, dim in comparison to the Bisy's. Due to soft edges and distance, the patch was hard to find when there was too much of stray light, unlike the Bisy's central patch due to its well defined edges and proximity. I feel that to be a deficiency, since I want to know whether I see a detail of the environment to the best degree I can or whether I could sweep the detail with the beam. Even in a complete darkness, the Hella beam appeared dim and made me insecure. My mind wandered to a regular incandescent. In his note on the Hella, Andreas Oehler mentioned a dark central patch in its pattern, but I did not find it in mine. Given the erratic features of the pattern, in particular the pronounced left-right asymmetry in mine, I can believe that there may be significant individual variations in the lamps to generate a dark patch. Andreas mentioned a low Zener voltage in the Hella. Given the differences I perceived in comparing the lamps with the battery and dynamo, I removed the Zener, but the very definite difference in brightness in the dynamo comparisons remained. (In an afterthought, I wondered about a possible difference in the operating resistances of the original bulbs in the two lamps, i.e. lower in Hella ?3W?, but did not dwell more on the issue during tests. To be explicit, with the battery I connected the lamps in parallel and with a rapidly driven dynamo I connected the lamps in series.) Overall, I was rather displeased with the Hella Micro-FF, having long ridden with Bisy. The only other lamp I had at hand for a comparison was the bottom line Soubitez with a regular bulb. The Hella in comparison was clearly superior. However, the gap between the Bisy and Hella was also significant. Pawel Danielewicz From: Pawel Danielewicz Subject: Re: [BC] Hella Micro-FF vs Bisy follow-up + bulb is a bulb... Date: Sat, 8 Dec 2001 14:35:07 +0000 Message-ID: <0.700001764.60088367-951758591-1007822108@topica.com> At 09:45 PM 12/5/01 +0100, Andreas wrote: Thank you for the detailed report. Before you finally judge the Hella against the BISY have a close look at the bulbs, at least exchange them. Their properties varies significantly. After the Hella Micro-FF gets equipped with a decent bulb, it becomes a decent lamp. The difference compared to Bisy is in the shape of the beam. The Hella's beam is shorter, wider and has softer edges. In terms of the width, the Bisy's beam fits a bicycle path while the Hella's a one-lane country road. When aimed to cover intermediate and farther distances, from above the wheel, the Hella leaves a bit uncomfortable region in front of the bike covered only with a faint glow. On the other hand, because of its longer column of light the Bisy can cover distances from quite close to far away. In detail, the Hella's beam looks on the ground like a cup with some shadows. Andreas Oehler mentioned a dark patch in the center. I do not have one, but instead two darker regions pinching the cup from the sides. At the level of the shadow of the front wheel, two narrow convex bright arcs appear, concentric with the beam, as if edges marking a plate under the cup. They can be distracting and even a bit blinding when there is stray light. The electric contacts with the bulb of the Hella are a bit flimsy. Overall, above the wheel or at the handlebar level, I think I prefer Bisy because it allows for the beam from up close to the bicycle. It is of an obvious advantage in the darkness and, when there is stray light, it gets easier to find the beam. Still, with a bright bulb, I found that the Hella gave enough illumination at intermediate distances to remember the details as they moved through the darker gap. If the Hella were to be mounted on the fork, the size of the gap would shorten. As this is where I normally mount the lamp, I will consider the Hella for my regular use. At this point in testing, I have four 6V/2.4W halogen HS3 bulbs at hand, two Philips and two Osram. There is no reason to believe than any one is significantly older than the other. The bulbs can be divided into three groups significantly differing in the luminous output: Ph I > (Ph II >~ Os-Bisy) > Os-Hella , where the lamp names indicate the bulb origins, and where the two separations between the groups are comparable. The change from the Os-Bisy to Os-Hella amounts to turning a decent lamp to an essentially unaceptable. This suggests that one needs to get a quantity of the bulbs and to sort them out. To make things worse, in my recent experience, two bulbs may differently compare in battery and dynamo operation. In Germany, a halogen bulb may be had in a department store for a little more than an issue of the Herald Tribune, but what is a consumer in the US supposed to do?! Would the brighter bulb be shorter lived? Otherwise, this certainly complicates the lamp comparisons. On the side, have you explored, Andreas, the Philips blue halogen bulbs? Pawel P.S. My previous post did not get through, possibly stuck on the server. I apologize if they double up.