Cycling UK Forum

rogerzilla wrote: ↑2 Sep 2024, 5:24pm Only the German approved ones gave a proper cut-off like a car's dipped beam.

There's a growing number of lights with a good cut off but without German approval, I give a couple of examples upthread. The reason they don't it is likely to be because they also have a flashing mode which wouldn't be permitted.

A dynamo light is always nice to have. With battery lights I find I always try to manage charge and don't use any light at maximum. So, some of the theoretical benefits of max brightness might never be realised.

Regarding getting more than 3W out of a dynamo, that is indeed possible, although many commercial lights that adhere to StVZO don't seem to do this. One reason is they try to be compatible with rear lights in parallel, and the standard is both must operate at 6V. I've seen lights with resistors in series solely to load the dynamo up so it reaches 6V. The more advanced ones have switching drivers, though.

The trick of putting two lights in series to reach twice the output (at speed), which seems to have been common with resistive loads like classic halogens, might be more complicated with switching drivers. E.g. if a driver is at 50% duty cycle, perhaps it could eke out twice the current at output, as the cycle may mimic a higher impedance (I have no idea if this is the case), allowing the dynamo voltage to rise. But two switching regulators in series may interfere with each other. E.g. if both were identical but 180 degrees out of phase, perhaps they would present a 100% duty cycle to the dynamo, which would load the dynamo down to saturation - although crucially at what voltage? This is completely theoretical of course, as an exactly identical pair of waves would be very unlikely, and smoothing capacitors may make this a moot point.

However, this is overthinking the issue slightly. With my own DIY attempts, it is very much possible to make a 7-8W dynamo light without a switching driver, and it will produce such output at the very speeds when it will likely be of use. Some single-unit commercial lights do this too, albeit only the most expensive ones. I don't think using a supercapacitor (or battery) to store extra juice for a boost mode is really necessary if the light already scales this way.

No light will illuminate an oil patch on a dark wet night.

I regularly ride pitch dark back roads. In the dry, my £300 Exposure light is as good as a car headlight, in brightness and beam pattern, allowing normal speed riding even on fast descents.

On wet roads the difference is shocking...far less light is reflected and this is where you actually need a light specced with so many lumens that to many it seems ridiculous.

If you ride dark unlit rural roads regularly....

Tip 1: buy as bright a light as you can afford.

Tip 2: set the bar bracket to a tightness that allows you to dip the light to avoid incoming traffic, by swivelling it down.

Tip 3: it's the deer and badgers that represent the biggest danger to life especially on fast descents.

rogerzilla wrote: ↑2 Sep 2024, 5:24pm Only the German approved ones gave a proper cut-off like a car's dipped beam.

British made Exposure have for many years been making arguably the best high power led road bike light with a car-like cutoff beam pattern. With dipping/full beam function.

Or like I suggest above, dip it manually, although this is maybe practical only where car encounters are infrequent I must admit (I'm in rural Scotland).

PH wrote: ↑2 Sep 2024, 12:00pm We are a bit spoilt for choice, we can find lights to match however we wish to ride, unlike a few years ago when we had to match our riding to the lights available. It's easy to forget that the second still remains an option.

My underlining, and in answer to the thread’s tittle (rather than the OP).

The above (by PH) was along the lines of what I was thinking this morning. Fit what you do to what you have, or can readily have, rather than pushing the boundaries of what’s available and still not finding anything quite good enough. What lighting is available is certainly very capable and far better than the stuff that used to safely guide riders through the night a generation ago. It should also be remembered that light from the sky isn’t replaced by light from a torch (in many ways they are different) and that light from a torch, with some limitations, only enables us to proceed into the (otherwise) dark.

My own front light is a mere 20 lux LED light and imho it’s significantly better than the 3 watt halogen light that once used to guide me safely through the pitch black - so it’s ‘obviously’ ‘enough’. As a big plus that ‘mere’ 20 lux is available from pretty much a walking pace. Whilst, in use, I’ve been very pleased with what I have my 20 lux LED (£20) is very much at the lower output end of what’s available, higher output lights are readily available for relatively affordable prices (I could buy 30 and 50 lux lights for £30 and £50 respectively). These days we’re actually spoilt for choice … and particularly so if we have reasonable expectations and modify our own behaviour.

If I had to buy a new light then I’d likely decide to ‘put a bit of fat on it’. ie. I’d spend an extra tenner (£30) to get a 30 lux unit.

TLDR: 20 lux at £20 is (imho) all you need, if you’re feeling flush, 30 lux at £30 would be nice. Ride within the light that you have available.

You should always adapt your riding (driving, walking) to the visibility. That goes without saying. I suppose it depends on your individual eyes, how fast you would naturally ride, how much you trust your reactions (and brakes and tyres), but I'm wary of saying that "we had this much in the past so we don't need more". Certainly, outside of well-lit towns, I never felt entirely comfortable with any lighting I had in the pre-LED era, at any speed. I've no idea how many lux or lumens is a decent minimum – and other factors, such as beam width, distribution, colour spectrum, are at least as important – but it is definitely possible to have "not enough".

CliveyT wrote: ↑2 Sep 2024, 11:50am The other thing to remember is our eyes are incredibly adaptive, so switching from 60 lux to 70 lux will look a lot brighter, but within a few miles you really won't notice any difference. So unless you know roughly where the oil spill is then above a certain point numbers don't matter that much

The original post has been answered so I can’t see the harm in digressing a little from it, and we’re still addressing the thread’s tittle.

There’s the law of diminishing returns to consider and then there’s getting into the levels of light that aren’t noticeably different to the adjusted eye. Powerful dynamo lights can be expensive and the £1 per 1 Lux relationship soon drops away. I’m not sure but powering a more powerful lamp surely has drawbacks: maybe it’s dimmer in the low speed (walking plus) range and maybe there’s more drag on the dynamo too. In terms of light output I’ve found what I think of as perfectly functional and a bit more than acceptable, but where the optimum points are I’m not so certain … and then adding individual’s factors into the ‘equation’ further confuses matters.

TLDR. You might prefer but you probably don’t need the fancy stuff - need, better, want and best are four different words that mean four different things.

Having read Carlton Green's posts, I thought I'd add its not just about the lumens but also the way the light is thrown put onto the road...
..I've got several 2nd hand dynamo driven leds, ones rated at 60 lux and the other at 70 lux. The issue with both is that each one produces a 'hot spot' of light in front of the bike.. this hot spot turns the normal dark grey of the tarmac into a light grey, and because its quite bright by default makes the other areas look artificially darker...
..infact I might be better of with a lower lux to reduce this 'hot spot' of light...

..looking at the way 'off road vehicle' leds are designed, I don't think cyclists are best served with a headlamp running just one very bright led.... I think we would get a better spread of light if bike head lamps were much wider and featured a strip of lower powered leds, to create a much more even throw of light...

..Philips was one of the first headlamps to use leds and as far as I can tell it remains the only dynamo headlamp which used two leds to produce a more regular spread of light..

cycle tramp wrote: ↑4 Sep 2024, 9:28pm ...

..looking at the way 'off road vehicle' leds are designed, I don't think cyclists are best served with a headlamp running just one very bright led.... I think we would get a better spread of light if bike head lamps were much wider and featured a strip of lower powered leds, to create a much more even throw of light...

..Philips was one of the first headlamps to use leds and as far as I can tell it remains the only dynamo headlamp which used two leds to produce a more regular spread of light..

The B+M clamshell reflector can spread the light well from one LED. Their more expensive lights and the Schmidt Edelux II, which uses their reflector, can do this. My Supernova light (see my avatar pic) also has a very well-distributed beam with no bright spots but it is not wide enough for riding tight curves.

cycle tramp wrote: ↑4 Sep 2024, 9:28pm Having read Carlton Green's posts, I thought I'd add its not just about the lumens but also the way the light is thrown put onto the road...

Indeed, Bmblbzzz covers it as "other stuff" the post immediately above Carlton's.
The difference between the original Edelux and the Edelux II is huge, despite them sharing the same power source and the modest increase in Lux. Whilst I agree with Carlton that want and need are subjective, better is very often quantifiable.

As Plancashire notes, B+M headlights use a design in which the LED faces backwards, towards the reflector, which then shapes the beam. It works very well at producing a bright but evenly spread beam, avoiding or at least ameliorating the hot spot problem.

As per other posters, lumens are irrelevant because the measurement doesn't account for how the light is effective in lighting up the road and claimed lumen output is not always reliable. I'd go further and say that lights that make a big selling point of high lumen output are often best avoided because their design tends to be driven by that and not on their efficacy in illuminating the road ahead without dazzling other road users.

For road use, I would only recommend StVZO (front) lights. Some have wider or narrower beam spreads and longer or shorter throw than others but all are effective by design. My B&M 80 lux lights are good for unlit winding country lanes at "reasonable" speeds and I am impressed with my much cheaper Büchel Tour LED Headlight (45 Lux) that I have on my utility/pub bike (though it can get very warm). A battery 30 lux light from Lidl that I've used was more than adequate for urban riding and good for unlit country riding at a "relaxed" pace.

For off-road riding where there are twist and turns, or rough surface that needs attention, I like to use a decent head torch (I use a Fenix HM50R that can output 700 lumens) so that I can see where I'm looking. I have used a powerful hand torch mounted on the handlebar as a high-beam floodlight but find that it doesn't offer any real benefit over the B&M 80 lux light coupled with the head torch.

Bmblbzzz wrote: ↑5 Sep 2024, 10:48am As Plancashire notes, B+M headlights use a design in which the LED faces backwards, towards the reflector, which then shapes the beam. It works very well at producing a bright but evenly spread beam, avoiding or at least ameliorating the hot spot problem.

However it’s achieved I’d have thought that the spreading the light and avoiding intense light spots would be best - a uniformity of moderate intensity in a central area and lower light levels to the side. The B+M headlights can, I think, be rather ‘pricey’.

Being a tightwad I wonder about spreading light by using two (already owned) lower powered lights that are pointed (forwards) towards two different points on the road ahead - near and far beam.

plancashire wrote: ↑4 Sep 2024, 9:55pm

cycle tramp wrote: ↑4 Sep 2024, 9:28pm
..Philips was one of the first headlamps to use leds and as far as I can tell it remains the only dynamo headlamp which used two leds to produce a more regular spread of light..

The B+M clamshell reflector can spread the light well from one LED. Their more expensive lights and the Schmidt Edelux II, which uses their reflector, can do this. My Supernova light (see my avatar pic) also has a very well-distributed beam with no bright spots but it is not wide enough for riding tight curves.

One of the led lamps to which I earlier referred, was a B&M lamp rated at 60 lux.. I shouldn't complain too much as it was kindly donated by my brother to me, to ween me of halogen bulbs.... don't get me wrong, it's a nice bit of kit (although somewhat battered).. and throws out some good light except for a square foot or two when the strength or wavelength of the light turn the tarmac a lighter shade of grey and removes some of the detail from it.... (or at least to my eyes).

....if you look at the way lighting is done in a large room, there is rarely one source of light... there's several sources to eliminate things like shadows and uncomfortable bright areas... (overhead bulbs and wall lamps, table lamps, standard lamps and so on)...

...cost wise a strong 60 lux (or more) headlamp seems to cost two or three times that of a headlamp which produces 20 to 35 lux.. if you could run two led dynamo headlamps of 35 lux each, that would be 70 lux in total.. (and perhaps at a lower purchase price than one 70 lux headlamp) you would also be able to play about with the beam patterns to suit you, by positioning the lamps at different angles and even different widths apart. .. and you may then have the back up of limping home with just one light should the other fail or becomes damaged..

..has any one tried using to lower powered leds together from the same dynamo? And if so what we're the results?

cycle tramp wrote: ↑4 Sep 2024, 9:28pm Philips was one of the first headlamps to use leds and as far as I can tell it remains the only dynamo headlamp which used two leds to produce a more regular spread of light..

That is going back about 15 year I think. I had one. A nice feature was that you could turn off the standlight when you stop to go to a cafe or whatever. On returning, switch on and you had instant light to see around to unlock perhaps.

The dynamo light produced a much narrower beam than the battery equivalent (which I still have) or the Edelux 2 that I have been using for the last 4 or 5 years. This made sharp corners in pitch black lanes a bit interesting.