Last night I got to spend a few minutes comparing the beams between the Supernova Airstream and the Busch and Muller Cyo. It was an interesting exercise.
The Airstream wins handsdown for brightness. It projects an even swath of light from the tire, well out in front. The Cyo’s beam begins a bit further out, then also shoots pretty far. Both lights shoot enough light out to relieve any fear of outrunning the beam. (image from Peter White’s site)
The Cyo beam, however, is not nearly as even. There are certain bright spots as well as shadows caused by the reflections off of the lens.
In comparing overall brightness, I’d say the Cyo falls somewhere between Level 2 and 3 for the Airstream. I should mention that I was riding just fast enough for the beam on the Cyo to “power up.” Its possible that it may be a little brighter at speed, but the brightness levels make sense given the Airstream’s 4 watt rating v. the Cyo’s 3 watt LED. Both lights use different measurements (Lumens v. Lux) to advertise brightness, so I can’t make a true comparison using their data.
(Image from Peter White’s site)
Where I think the Cyo pushes ahead though, is with spill light. Those reflections throw some random light a little further out to each side. This is nice at reducing the tunnel effect on really dark nights; as well as rolling into turns. The Airstream, with it’s Terraflux lens, creates a very sharp cutoff – the view is either lit or its not. I think you could actually park the bike with the unit on; and draw a chalk line around where the beam hits. There are “logo lights” on the sides of the housing, but these are pretty much worthless because of hand placement on drop bars. I didn’t notice any real amount of spill coming off of them anyway.
So having the brightness of the Airstream is great, although I think it borders on overkill and I will most likely use Level 2 to get a little more time out of the battery. But having the wider beam of the Cyo, not to mention the convenience of the dynamo hub and taillight, also represents a good light and an excellent bargain.
I think choosing between the two configurations becomes a matter of personal need. If I had only one bike, and I did a fair amount of night riding, I’d choose the dynamo/Cyo. If I had more than one bike, but only funds for one light, and I’d be riding those bikes after dark; then the Airstream might be a good choice. As far as touring…while there usually isn’t a lot of night riding, and the Airstream can function as a flashlight; obtaining a charge could be a deal-breaker.