Originally Posted by
Looigi
Watt rating is one of the least useful as it's the power input to a light, not the light output. For example, a 1W incandescent bulb would be useless as a bike light whereas a 1W LED could provide a useful, albeit rather low, amount of light because LEDs are much more efficient than incandescent lamps.
Lumens is a measure of total visible light output. Accuracy and truthfulness of measurements vary. How that light is distributed is also important. Lux is a measure of the maximum brightness in a beam (Lumens per square meter). For a given Lumen output, a more tightly focused beam provides higher Lux. Taken together, Lux and Lumens give a descent idea of how a light might perform, but they still only convey the total light output and the brightness at the center of the spot, not how the light is distributed around the center of the beam.
But again not all light manufactures rate their lumens honestly. The only way you can determine a light's effectiveness is to look at the comparisons sites I mentioned in my first post, unfortunately not all the lights on the market are shown, but at least most of the major brands and a couple of generic Chinese brands are.
I do believe the wave of the future, started by Phillips, will indeed be aimed optics, so instead of a round flashlight beam requiring 3 to 4 times the power they will be more like motorcycle and car headlights where the beam is aimed flat, after all no one cares about seeing the tops of trees! And as a bonus as the light output drops but illumination increases your battery can be smaller and could last longer depending on how small the battery gets of course. This inaccurate reporting of lumens by manufactures is very much akin to the highly inaccurate wattages reported by consumer home electronics, a $350 Sony surround sound receiver in no way puts out 1200 watts of sound while only consuming 45 watts.
By the way here is a 5,000 lumen light, probably closer to 1500 lumens due to the rather small battery required to run it either that or the run time is about 15 minutes:
http://www.ebay.com/itm/SolarStorm-5...80939592837%26
Here is a review of the cheaper 1800 lumen generic Chinese light, note his conclusion of what he things the actual lumens are:
http://forums.roadbikereview.com/com...mp-269236.html
Also I found out that several of the Generic Chinese brands I had time to look at all used the same battery, the one in the review used a 6400mah battery as did the one I showed in my first post as does the 5,000 lumen one I showed in this post. Meaning of course that the battery will not last anywhere near as long in the 5,000 light vs the review of the 1800 light. But these lights do represent a great value for the money, even if a particular light only lasts 2 or 3 years in the long run they would be cheaper than a MagicShine mostly because MagicShine replacement battery will cost more than the generic light but also the MagicShine life expectancy is not all that great (I don't consider 3 years as a great example of life expectancy when I have a light that is 6 times older than that!)