Forum home Commuter cycling forum Commuting general

Lights

Vaughan1Vaughan1 Posts: 65
edited December 2014 in Commuting general
Hi. I am sure I am not alone in being very confused when looking at lights. Watts, lumens, Lux etc etc. So who has say a table so these can all make sense. I went Hanford to have a look and they had lights at 2.5lux as suitable for unite roads. As far as my understanding goes 1 Lux is 1000lumens per square meter. But how useful this amount of light is I know not! Any experience or understable info would good. Just to add to the confusion price seems to bear no relevance either.

Posts

  • I've never understood this kind of thing and don't have any desire to.

    For something understandable the Exposure site is quite useful (go to the Light Comparison bit):

    http://use1.com/exposure-lights
  • dj58dj58 Posts: 2,139
    http://www.ctc.org.uk/article/technical ... andles-lux

    http://www.bicyclelightshop.com/pages/b ... -explained

    http://www.bicycle-and-bikes.com/bicycl ... rmats.html

    I have one of these for unlit roads, used a the full 700 lumen dynamic setting, angled correctly it does not dazzle oncoming traffic. Can be switched down to 300 lumen and 100 lumen plus Hyper constant and flash modes. Not cheap but the best I have had to date. http://www.cateye.com/en/products/detail/HL-EL470RC/
  • The RookieThe Rookie Posts: 27,747
    From my experience you need at least 500 lumens for cycling on an unlit road, lux doesn't help as you can get a hi. Lux by putting all your light into a small area (of course the beam pattern on your 'lumen' light can be poor!).

    I like my Lezyne Macro drive, 550lumen, excellent beam pattern, compact and lightweight, not the brightest though, but I find it more than good enough.
  • whoofwhoof Posts: 756
    You can think about Lumen and Lux a bit like force (related to mass) and pressure (force over an area).
    An elephant exerts a large force on the ground as it's heavy, a 50kg woman exerts far less force.
    An elephant stands on your one of your feet and the woman stands on the other in stilettos (you're in a fetishish circus type place). The foot with the woman is going to hurt more as the force is over a smaller area so has a larger pressure.
    The Lumen like force is the amount of light emitted and the Lux like pressure is the amount light over a square metre.
    A Watt is a unit of power (one joule/second) and Lumens/Watt is how efficiently that power is turned into light. i.e. a Fluorescent bulb has a lower power usage but getter light output than an incandescent bulb and is therefore more efficient.

    Therefore buy some nice bike lights.
  • whoofwhoof Posts: 756
    gbsahne wrote:

    The wiggle one is actually very useful.
    The only thing is if you compare an Exposure Joystickwith Moon Meteor it looks like it has the power to trim the hedge and put up gate.
  • Thank you guys. Good sites especially the compare ones. Pricey though for the car headlamp replacements.
  • InitialisedInitialised Posts: 3,047
    Vaughan1 wrote:
    Hi. I am sure I am not alone in being very confused when looking at lights. Watts, lumens, Lux etc etc. So who has say a table so these can all make sense. I went Hanford to have a look and they had lights at 2.5lux as suitable for unite roads. As far as my understanding goes 1 Lux is 1000lumens per square meter. But how useful this amount of light is I know not! Any experience or understable info would good. Just to add to the confusion price seems to bear no relevance either.

    Just buy these, swap the mount for a Cateye (trimmed to fit) and stop worrying:
    http://www.ebay.co.uk/itm/6600LM-3x-CRE ... 43c8bc236f
    I used to just ride my bike to work but now I find myself going out looking for bigger and bigger hills.
  • supersonicsupersonic Posts: 82,708 Lives Here
    This is part of a guide I wrote in the MTB section:

    Manufacturers often quote many figures with their lamps, such as lumens, runtime, candela, amp-hours and all manner of jazzy words that many simply don't understand. Quite often they exaggerate the figures, or quote spec from the LED manufacturer rather than testing what their units are actually outputting. Actual lumen output depends on the LED, the drive current, and losses from reflectors/lenses and electronics. Here is a lowdown on terminology:

    Lumen: a lumen is the scientific unit for the 'luminous flux' - in simple terms it is the amount of light that a source is producing. The higher the figure, the more light (photons) is emitted, but this does not always mean that it appears brighter - it depends how concentrated the beam is. More lumens consumes more power for a given efficiency.

    Lux: the unit of illuminance (and luminous emittance) that is, 1 lumen per square meter.

    Candela: a candela is the scientific unit for 'luminous intensity' - basically how concentrated the light beam is and is equivalent to 1 lumen per steradion (solid angle). But as above, it doesn't tell the whole story. Imagine a laser bean. Very intense, high candela rating, but you wouldn't light a trail with them as are far too narrow!

    Beam pattern: is the beam uniform in brightness? Some are, many aren't, with a central hotspot. What is best here is often personal preference. Photos of the beam can be useful to compare (if camera setting are equal for a fair test)

    Beam angle: different lamps will output their light over differing angles. This can be a artefact of the LED, lensing and/or reflectors. A wide flood type beam can be useful to illuminate a large field of view, but a more spot type lamp can often pick out objects better. If two lamps have the same lumen output and even beam patterns, but one of them spreads it over twice the angle (or four times the area), then this lamp will appear to be a quarter as bright.

    Amp-hour: this is a unit of electrical charge and is related to the battery cells and runtime. For a given voltage, a larger amp-hour, or milliamp-hour figure results in a longer runtime.

    Runtime: how long the unit will run for. Many lamps have multiple power settings so be aware that very long runtimes may be at the lowest settings.
Sign In or Register to comment.