Originally Posted by
Telly
I've been reading (and have posted) in this thread from day 1, and IMHO, I believe that you are missing the point on bicycle lighting. To explain this, I prefer to give a real world example with a couple of different light I already own and use on my nightly commutes.
I recently bought a MagicShine clone supposedly rated at 1800 lumens which had a very bright spot beam which only a very small portion was utilized for viewing the road (city streets). After a fellow forum member suggested, I went ahead and purchased a diffuser lens which replaced the original clear lens and threw a much wider beam across my path, with a big hit on the distance ahead, but overall a major improvement.
And for the comparison; I have a B&M CyoT (properly aimed via the instructions) driven by a dynamohub on my other bike which is rated at 60 lux, with my guesstimate of around 200-300 lumens (compared to other quality lights I've seen).
Even though the MS has a more powerful light source, the CyoT is a far better light for commuting since the optics on it almost 100% utilize the light with almost no side spill and total vertical cutoff. I have never been told of having the light shine onto cars or pedestrians, or fellow cyclists, which is not the case with the diffused MS.
At least in the urban environment, more is NOT better if you have the majority of the light shining on everything except where it should be focused on.
That's my 0,01 cents and I hope I didn't come out condescending.
I don't total disagree but for different reasons. However, a couple of issues to address first. It is helpful if you use the "Reply With Quote" button when you reply to posts. Using lets everyone know to whom you are addressing your comments.
It took me a long time to understand why the "1800 lumen" claim on lights was wrong. I'm not an electronics guy but I can learn. The Cree emitter that is used on these lights has a maximum output of around 700 lumens. The claims of 1800 lumens is highly inflated and I wish that the manufacturers wouldn't do that but they do. We just have to live with the claims and understand that the output is more realistically in the 600 to 700 lumen range. That, by the way, is about what a car provides per lamp on low beam. Now on to the lights.
I think you are misunderstanding what you are seeing for the clone. Magic Shine and their clone lights use a reflector that is about a 35 degree flood light. That means that the light intensity across the beam is greatly reduced. It will have a central hot spot but all lights have that. The rest of the light will be spread out over a large circle on the ground. When you add a diffuser, you are increasing the diffusion of the beam to something similar to a 50 degree flood light. If the light were evenly spread over the beam, a 35 degree 600 lumen light has a lux of 77. Diffuse the light over a wider area with a wider angle and the lux drops to 35. Going to a diffuser or even a wide angle flood light shots more of your light off into directions that you don't want it to go.
Going to a tighter beam puts more light in a smaller space, which is what the CyoT does as well as other tighter beam spot lights do. All you've done is purchase a narrower spot light and noticed that you have a better beam. I use a spot light...not a Magic Shine clone but another type of LED...which has a reflector angle of about 20 degrees. Back in my halogen days, I use a beam that was 12 degrees and a 7 degree spot. Because of the very tight angle, you don't get much spillage outside of the beam's hot spot and glare is reduced. In fact the 7 degree beam was too tight. You need a little spillage outside of the beam or you end up with tunnel vision.
I agree that more isn't better if you diffuse the light all over everywhere. But I don't do that. I want...and get...a bright coherent beam that lights up what I need to be lighted while still providing enough illumination to be seen against a sea of lights in an urban environment.