Join Date: Jul 2008
Location: Austin, TX
Bikes: Giant OCR2, Bridgestone RB-T, Bike-E, Vision R-40, Novara Safari
I haven't run that specific light, but I've bought zoomable lights on eBay before.
In my case, the LED had a lens in front of it that you could move back and forth (by screwing the head in and out) and that was the zoom. And it worked fine.
HOWEVER, there was no reflector in the light -- just a LED with a lens in front. So presumably this light was wasting at least half the light emitted by the LED right off the bat. They could add a reflector and fix this, but it would screw up the ability of the lens to focus the beam -- it would cause the beam to be less focused.
So, which is more important? Being able to precisely control your beam, or getting as much of the light from the LED out in front of you?
Personally, I think #2 is more important (as a reflector make a pretty decent beam pattern as well), so I won't be buying any more of these lights. That said, it's not a bad light (the one I have, which is not the one you're looking at), just somewhat less efficient than others with the same emitter.