Wednesday, January 13, 2010

Light brightness

I know of at least 4 different bike lists that Alex posts to on a regular basis. I also know that Alex is really good at his "real" job (we sort of work together). And watching his blog, it's clear the guy gets a lot of other stuff done. There's also other non-bike related interests that Alex spends time pursuing (electronics, computer stuff, fish stuff, beer making, home projects, etc). It's not clear to me how he does all this. But some common Alex traits thread their way through all of these pursuits: honesty, curiosity, and creativity.

Anyway, that's the Alex backstory.

The following was taken from a thread on a bike list at work. Some guy posted the chart below and then below that is Alex's reply.

I found it particularly enlightening. Or should I say illuminating? (I've been watching too many Hitchcock intros).



Claimed Lumens

Measured Lux

$ per lux

Ayup 2010 bar V4 Adventure System (Full Review here)





Ayup 2010 helmet (Full Review here





Baja Designs Stryker





Exposure Toro (Full Review here)





Exposure Diablo (Full Review here)





Exposure MaxxD





HID Technologies Lumen8r Quad





Lupine Tesla 4 (Full Review here)





Lupine Wilma 5





Lupine Betty





Magicshine MJ-808 (Full Review here)





Niteflux Enduro 8 Single



NiteFlux Max Extreme 2





Niterider Pro 600





Niterider Pro 1200





TrailLED Darkstar





Says Alex:

This chart shows while Lumens are such a silly way to measure lighting.

Lux is the intensity of the light over an area. Lumens are the total intensity of the light. You can have something with very high lumens distributed over thousands of square meters and the light wouldn't be noticable at all (so the lux would be very low). The same number of lumens could be concentrated into in one square mm and probably burn a hole through something (the lux would be very very high).

The headlight that I use (a generator headlight called the IQ Cyo) is 60 Lux, but uses a LED that only puts out around 150 lumens (CREE XR-E). The lenses just do a good job of putting the light on the ground in front of the cyclist, and not wasting it lighting up trees that are over the road or trail. The MS has 6x the number of lumens, but puts less light onto the ground becuase the light is being distributed everywhere. A lot of that scattered light is going into the eyes of oncoming cyclists and driver's, blinding them.


rory said...

alex sums it up pretty good. if you ever get into roadway design, then you do measure the intensity of a light over a statistical area. the standards then have requirments for average, max, and min intensity.

if lighting design for bicycles gets to be standardized, this would be a good method. establish an acceptable area, and then each bike light has to light this area with a minimum average, and not to exceed a maximum.

of course, this would require more design then just putting the brightest bulb in a fixture, and calling it good. also, those really, really annoying blinkies people put on the front of their bike would hopefully be extinguished from existence.

John Speare said...

My guess is that Germany has such standardization and requirements. I know blinkies are verboten. And all the good lights come from Germany. And reflective sidewalls are required. Germans are apparenly pretty serious about bike illumination.

Mike Sirott said...

I just got my MagicShine in the mail a few weeks ago. It's awsome. It's not made to the same quality specs/tollerances as my L&M or NR lights, but for 1/4 the price, I'm happy.

Dan O said...

You have a great blog going here - awesome.

I've been using Magicshine lights for a few weeks now - killer deal for the dough. If interested, my own little review here:

Some fellow riding pals are just as happy with 'em as well.

Anonymous said...

Watts -> Lumen -> Lux -> ?

Anyway, those magic shine are fine for commuting but I wouldn't recommend for off-road use... the battery pack needs to be sealed and shock-proofed better. It is nice and safe in my pannier though. I may water-proof it later but i don't think i can do much about shock-proofing the control board in the battery :/

After spending lots of money on crappy systems of the past(BLT) I don't waste much money on stuff like that.

John Speare said...

Dan- thanks for the nice words.

Anon: I agree, I think off road riding is a whole different ball of wax. Having a lot of diffused light AND a focused (helmet-mounted) light would seem to me to be a good approach. Though I've never done a lot of non-trivial off-road at night.

Ed D said...

A few of the numbers in your chart are incorrect. For example, the Baja Designs Stryker (3rd on the list) should read 52 lux, not 5, for your "$/lux" statistic to be true.

$298.00/52 lux = $5.73/lux, the number on your chart.

This 52 lux reading would match the findings of the independant comparison.

John Speare said...

Thanks Ed. Fixed it.