Sigma Ellipsoid Plus, Bisy/Schmidt, and other lamps

From: Pawel Danielewicz

This is an evaluation of the Sigma Sport Ellipsoid Plus and Bisy/Schmidt lamps. Lumotec and Union lamps and my own standlight are used for comparisons.

Sigma Ellipsoid Plus is an upgraded version of their Ellipsoid halogen lamp run from rechargeable batteries. The lamp and batteries are in one housing that mounts on handlebars with a click-type plastic mount. The Plus allows for attaching a dynamo and a dynamo driven rear lamp and it provides a standlight function. The dynamo plugs into the same phone-type jack as the charger. The wire from the rear lamp attaches to pointlike contacts in the housing of the Plus through a slide mechanism characteristic more of bike computers than lamps.

With the power from batteries on, the lamp switches to the dynamo at a rather high threshold, higher than from requiring that the light powered by dynamo be completely white.

When bike stops the light first goes out and then after ~0.6s switches to batteries. With the power from batteries off, the standlight function is activated just by operating the dynamo for a while. After the dynamo goes off the light is powered from batteries for about 4.5min. If the batteries are weak so that the light slightly yellows, the batteries shut off and an LED flashes. The lamp may be taken off from the handlebars and used as a flashlight.

The circuitry inside the Sigma Plus consists of chip, 4 diodes, 4 resistors, a capacitor, and a relay. The standlight function is operated by the relay. When the power is taken from the dynamo, the relay lets the AC through to the lamp. It is not clear that the chip has anything essential to do with the standlight function. At high speeds, the dynamo charges the batteries.

The standlight based upon the relay, with the AC going through when the power is taken from the dynamo, with charging of the batteries at high speeds, appears to be a similar solution as in my own standlight. The advantage of my own standlight is that it just dims momentarily when switching from the dynamo to the batteries, rather than going off. The advantage of Sigma is that it can be activated by dynamo alone without flipping a switch. (This may be a drag with Schmidt, though.) I like better the lower threshold for dynamo power in my own standlight. As to the batteries shutting off in Sigma, I prefer a yellow light than none at all. The Sigma standlight is tied to the particular light which is so so (see below).

Having to mount the light on the handlebars is limiting, e.g. I have a basket in front and there is no way to mount the lamp without the basket getting in the way of the light. (More than half of the bikes in Germany, where the lamp is marketed, have a front basket.) Mounting the lamp and attaching the wires each time the bike is ridden in the evening is cumbersome. (Sorry, you guys with elaborate battery systems.) The phone jack for dynamo is covered with a rubber patch that is difficult to move even in full daylight. The ability to use the lamp as a flashlight balances a little bit the disadvantages.

Now to the assessment of light from Sigma Plus, Bisy, and the two other lamps. It should be mentioned that the design of the Bisy lamp has been purchased by the Schmidt company (makers of the best hub dynamo) and, with possible modifications, will be hopefully marketed by them in the future. The Bisy company is now owned by Marwi which also owns Union. OK, my criteria are as follows. I want to have a bright beam with well defined boundaries that illuminates in a reasonably uniform fashion the path in front of me, that I do not need to readjust all the time as the environment changes. Irregular borders of the beam confuse the eyes. Similar is the effect of a spiky top boundary or light scattered to the sides especially with patterns. (Some scattered light is OK.) Given how a light is mounted, for a good illumination the beam should have a rectangular or trapezoidal shape with a wider bottom. The top of the beam should be the brightest given that it illuminates the farthest area.

From the 4 lamps I tested, Sigma was the poorest. The outline of the beam was quite erratic with plenty of scattered patterned light. Next came Lumotec. The outline was better defined but still quite blurred and there was a good amount of patterned scattered light. The Union was better with well defined beam and noticeably less scattered light. I may mention here that general opinion is that the Lumotec is better than Union. Union may be bought in Germany in supermarkets or department stores where it represents, though, the top of the line. Lumotec is, in practice, available in the bike stores.

Someone mentioned in the bikecurrent that Lumotec is better sealed against the weather than the Union and it may be true. With side by side comparisons of the beam, however, the cheaper Union beats the Lumotec. (Sorry, Lumotec owners.) Anyway, Bisy is superior to the three other lamps. The scattered light is weakest and least patterned. The beam is defined as well as in the Union but and it has a shape that is a taller rectangle than in the three other lamps. The brightness of the top is more pronounced than in the other lamps. When mounted, the lamp illuminates the largest spread of distances from the four, with a good illumination of the close and the far distances. Thus, there is little temptation to readjust the beam when condition change. The lamp is a winner for me. The only drawback in the lamp, I can see, is a slight coloring of the beam that appears to be due to the dispersing properties of the plastic in the front of the lamp.

Just few comments on the construction of the lamps. Lumotec, Union, and Bisy/Schmidt are all round, with 7.5cm outer diameters for the first two, and 8.5cm for the third. The outer ring of the front surface in the first two is used for a reflector, leaving ~4cm of diameter for the mirror for a halogen. Bisy gives up the reflector and ~7cm of the diameter is used for the mirror. The larger the mirror, obviously, the easier it is to focus the light. The sealing of Bisy seems to be just about as good as that of the Lumotec. My worry now is how I replace the Bisy when it gets stolen. (I’ve got it as a gift from Andreas Oehler.) I hope Schmidt decides to put it soon into production.

Pawel Danielewicz