I've come to the conclusion from trying lots of lights and a lot of reading that good reflector design is very task specific and ofter overlooked. This thread was started because some reflector design issues were taking other threads off topic.
For my first musing I'll be talking about using a flashlight to walk at night, I would assume this is a common task for flashlight use.
When you walk with a light what do you do. You shine the light down the path in front of you. Lets say 50 ft or so because you want to know what is coming up. When you are walking you do want a wide spill so you can see your feet as well. If you have a narrow spill you have to angle the light so the spot is only a few feet in front of you, this is undesirable. Now as you double the distance an object is away from you you have to increase the Lux by a factor of four for it to appear the same brightness. This is why you want a beam that has a well designed transition from spot to spill (preferable logarithmic **EDIT Sorry its the inverse square law **EDIT**).
Lets take the case of a light that has a tight spot at a very high lux level then has a sharp transition to a spill beam at a much lower lux level (McR18, Fenix). When you shine this light down the path, it is pretty bright at your feet, then your eyes perceive that the ground gets dimmer and dimmer the farther away it gets until you reach the edge of the spot beam where it gets very bright again.
The goal for path walking is a light that lights up the path an equal amount as it progresses away from you. This is more important the faster you are moving, aka cycling, driving. Car lights are designed this way.
The HDS light does a good job at this, the FF3 as well. I think the U2 isn't the greatest for walking because its narrow spill angle.
So reflector design is task specific and always a bit of a compromise. The McR18 reflector in my Spy is good and an excellent overall performer, but maybe not the best for walking. This is not a knock against Don's design, he understands this. When the Joker LED's came out, Don actually liked the wider beam, but he came out with a joker specific reflector because CPFers demands tight bright spots that perform well on white walls.
For my first musing I'll be talking about using a flashlight to walk at night, I would assume this is a common task for flashlight use.
When you walk with a light what do you do. You shine the light down the path in front of you. Lets say 50 ft or so because you want to know what is coming up. When you are walking you do want a wide spill so you can see your feet as well. If you have a narrow spill you have to angle the light so the spot is only a few feet in front of you, this is undesirable. Now as you double the distance an object is away from you you have to increase the Lux by a factor of four for it to appear the same brightness. This is why you want a beam that has a well designed transition from spot to spill (preferable logarithmic **EDIT Sorry its the inverse square law **EDIT**).
Lets take the case of a light that has a tight spot at a very high lux level then has a sharp transition to a spill beam at a much lower lux level (McR18, Fenix). When you shine this light down the path, it is pretty bright at your feet, then your eyes perceive that the ground gets dimmer and dimmer the farther away it gets until you reach the edge of the spot beam where it gets very bright again.
The goal for path walking is a light that lights up the path an equal amount as it progresses away from you. This is more important the faster you are moving, aka cycling, driving. Car lights are designed this way.
The HDS light does a good job at this, the FF3 as well. I think the U2 isn't the greatest for walking because its narrow spill angle.
So reflector design is task specific and always a bit of a compromise. The McR18 reflector in my Spy is good and an excellent overall performer, but maybe not the best for walking. This is not a knock against Don's design, he understands this. When the Joker LED's came out, Don actually liked the wider beam, but he came out with a joker specific reflector because CPFers demands tight bright spots that perform well on white walls.
Last edited: