F
On May 7, 12:01 am, SMS <[email protected]> wrote:
> Prisoner at War wrote:
> > Anyway, a good reminder, your post. I almost never feel the need for
> > a light, but all club rides require them (except the anarchist Time's
> > Up! rides -- hooray!), and, in keeping with my nature, if I get
> > something I'd like to get the best. ^_^
>
> I'm glad to see more night rides by clubs. Some clubs are very explicit
> as to the brightness of lights that are required,
Oh? How do they measure brightness?
> but any available HID
> light should be sufficient, usually the minimum is a 6 watt
> quartz-halogen headlight...
"Usually"? I'd like to see some citation for that.
> With the HID and MR series of lights, you don't really have to worry
> about blinding other cyclists, as the optics on these are very precise.
>From what I've seen, the optics on HID and MR lights are very precise
only in that they don't throw light out the back! They do throw a fog
of light out the front, _roughly_ in an eight degree (fairly typical
spot) or 30+ degree (fairly typical flood) radially symmetrical
pattern. IOW they throw as much light up as down.
Compare this with the optics on, say, my car headlamps, my motorcycle
headlamps, or my bicycle generator headlamps. All these direct less
light upward, since more light is needed downward onto the road. The
cutoff plane is easily apparent. They use the light output
efficiently.
Remember, light going upward toward other road users travels directly
from your lamp to their eye. It doesn't need to be as powerful as
what goes down. The downward light must hit the road, where some gets
absorbed and some gets scattered. Only a small percentage bounces
back to your eye to show you the road.
You need bright light down, much less light up. Radially symmetrical
optics don't do that.
- Frank Krygowski
> Prisoner at War wrote:
> > Anyway, a good reminder, your post. I almost never feel the need for
> > a light, but all club rides require them (except the anarchist Time's
> > Up! rides -- hooray!), and, in keeping with my nature, if I get
> > something I'd like to get the best. ^_^
>
> I'm glad to see more night rides by clubs. Some clubs are very explicit
> as to the brightness of lights that are required,
Oh? How do they measure brightness?
> but any available HID
> light should be sufficient, usually the minimum is a 6 watt
> quartz-halogen headlight...
"Usually"? I'd like to see some citation for that.
> With the HID and MR series of lights, you don't really have to worry
> about blinding other cyclists, as the optics on these are very precise.
>From what I've seen, the optics on HID and MR lights are very precise
only in that they don't throw light out the back! They do throw a fog
of light out the front, _roughly_ in an eight degree (fairly typical
spot) or 30+ degree (fairly typical flood) radially symmetrical
pattern. IOW they throw as much light up as down.
Compare this with the optics on, say, my car headlamps, my motorcycle
headlamps, or my bicycle generator headlamps. All these direct less
light upward, since more light is needed downward onto the road. The
cutoff plane is easily apparent. They use the light output
efficiently.
Remember, light going upward toward other road users travels directly
from your lamp to their eye. It doesn't need to be as powerful as
what goes down. The downward light must hit the road, where some gets
absorbed and some gets scattered. Only a small percentage bounces
back to your eye to show you the road.
You need bright light down, much less light up. Radially symmetrical
optics don't do that.
- Frank Krygowski