Is the brightness/light output of a bike light simply determined by the amount of lumens or are there other factors ?

I can see plenty of examples of unbranded lights and torches that are a fraction of the price of branded stuff but have much higher lumen ratings, why ?

Talk to me.

Yes and no.

Most manufacturers quote the theoretical lumens, a bit like car manufacturers telling us that a car has 200bhp.

In reality its probably less than that, and there are further losses through the transmission/lense.

And you could put a huge LED behind a crap reflector/lense and get a rubbish light, either too wide/too nearrow or with an uneven distribution etc.

And build quality/spares/backup will differ, yes spending £600 might not gaurentee you great customer service, but it wil be better than spending £50 on a light from the far east on which your basicly saying they’re disposable after they stop working.

as far as I understand it (which isn’t very far)….

– theoretical lumens are generally a lot more than actual lumens, due to losses.
– the reflector/beam pattern has a lot to do with how usable/bright the lights are.

Obviously if you have more lumens to start with you can afford to lose more and still be brighter, but then you are wasting battery power.

It’s all very well having millions of lumens but if they’re being sprayed all over the place rather than actually lighting the places they’re needed then they’re wasted.

I’ll take good reflector design and sensible beam patterns over mega lumens any time.

no.
lensing plays a big part. distribution of light, and to a lesser extent, losses. also many LED light manufacturers quote maximum output from the highest binned of that LED type, when often, it’s not that grade of LED being used in the lamp housing that you will actually get. ( for binning, think like all computer processors are made to run at maximum speed, but only some will be stable at that speed, which is why you get the same processor types but at different clock speeds. similar deal with LEDS, ‘cept it’s output that is graded. ).
get a DX one. or two if you’re feeling flush. 🙂
you’re worth it.

still riding in?

What he said, ——^

Buy 2 DX lights, accept that they might not last forever, but you’ll be safe in the knowlage that when they fail you can buy next years magicshine light which will probbaly have more lumens again and still be much better off finaincialy than if you bought the expwensive one.

Even that £6 light people link to is brighter than the small exposure/hope lights! It might last a month, but at that price who cares, you could equaly drop the hope in a hedge on its first ride,a t least with cheep lights you don’t worry about them failing.

what is a dx one ?

still riding in?

had a couple of days off cos of the ice but i’ve just had an op so i’ll be off the bike for 10-14 days min.

It’s also about colour rendition. I have a MTE P7 torch, a Hope 4 and an old set of Lumis. The Lumis are by far the dimmest, but they emit a broad spread of light wavelenghts, so colours come out far better. The P7 is very blue/grey and the rendition is appalling – roots just blend into the mud and it’s very difficult to distinguish detail. The Hope 4 splits the difference. Presumably higher quality emitters than the cheapo P7.

yes, i’m with you on the colour thing. much prefer yellowy light to stark white/blue light.

however i’m on a budget so i’ll have to put up to bumping into things if leds are cheaper or more available.

thanks all for your input so far but I need to know what these dx things are so i can search for them online, is it just the topeak £25 thingies that you’re talking about ?

dx = dealextreme.com

lots of cheap electrical/electronic bits and bobs.

You’ve only got to look at car headlights as a principle. A HID bulb is seriously bright, but when numpties drop them in to their standard headlights without appropriate lenses or a purpose designed Projector lense to focus that beam you end up with light scattering everywhere and the usefulness of such a powerful bulb is cancelled out.

This goes out o all Corsa drivers that blind me with blue tinted dazzleyness 🙁

There must me 101 links on here to the DX P7/magicshine light its about £50 and takes arround 5 weeks to arrive.

They have faults, but not insurmountble, and can be faulty (some peope have chargers that get really hot, battery packs exploding or not chargeing etc, but mines been fine so far.

DX link

Trouts picture in this thread demostrates to much lumen concentration/poor distribution http://www.singletrackworld.com/forum/topic/troute-mini

8)

thanks all

keep the recoms coming

Troutie also has a comparison of the Lumen/LUX drop at the side of his light as well as the DX Light.
That demonstrates I guess that different light designs and different lenses effect the light spread and usability.

http://troutie.com/?page_id=972

No, its not just about lumens, hence why beamshots can be useful.

Failing that, Lux readings, if properly recorded and presented, can offer a numerical representation of beam pattern from a light.

As for quoting theoretical numbers. Yes, some manufs do this, for obvious reasons. They get to quote massive numbers, and they save on the cost of independant measurements being taken.

However, I would point out that I for one, have gone to the time and expense of having a lab independantly measure my lights.
So, the lumen figures quoted for my lights are actual, real world results.

Cheers

😉

getting the prehensile toes sorted out eh?

DX Light

this is the one Tim has. sure he’ll let you play with it if you ask nicely, and give his views. it has the updated battery pack, but the cheaper head unit ( functionally the same ).
you’ll need an adaptor for the charger plug, i’m sure you have those kicking around, but if not DX do them for buttons too. the charger is universal supply voltage, so you don’t need a fancy adaptor.

otherwise if you’re feeling really flush, if it were me i’d look very closely at trout’s lumen liberator. looks reet fancy.

As the guy who has measured the Trout and Luminous lights in my lab, and compared them to the magicshine, I can say that it’s definately not all about lumens.

For a start, most manufacturers state the theoretical max lumen output of the LED. as an example, the magicshine light I have states “900 lumens”. I measured it between 500 and 550. A german lab also measured it at 550.

Both the Trout and Luminous now show real lumen values. eg the LL is theoretical max of 2100 (I think), but comes out at 1700.

Lux is a measure of how bright the light seems at some set distance infront. A very focussed beam can have a high lux, but a low lumen.
A good example is the luminous 401, lower lumen than the 601, but higher lux as it’s designed for a more focussed beam, ideal for a head light.

If you can strech to it, go for a Trout or a Luminous light. Both very good with a lot of thought behind the Lumen output and beam pattern.
Which one to go for will depend on riding style and personal perference as there’s not much to choose between them.