Tail Light - LED vs Incandescent
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Thread: Tail Light - LED vs Incandescent

  1. #1
    Member jbergen's Avatar
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    Tail Light - LED vs Incandescent

    There seems to always be a thread about moving to LED lights on these old bikes, and a bit of controversy over which is brighter/better etc. I recently switched to LED on my '78 CB400 and decided to figure out what the differences are between the two types of bulbs in terms of brightness and visibility. Anecdotal accounts swing both ways with some people claiming LED is brighter, and others that incandescent is brighter.

    Initially I tried to take lux measurements of the light using a light meter, but quickly determined (and verified) that the light meter I have is not accurate for LED light. So I reached for my DSLR instead. My method was to take three photos of the tail light from the same position in hi/lo and from straight back (0°), and an oblique angle (~40°) to measure visual brightness. Using my DSLR I set it to manual and stopped down the exposure and set the shutter to 1/30sec to make sure I didn't catch the LED off cycle (LEDs blink at 60hz). No matter how bright the light, the camera takes the same photo (in a sense) and makes a visual comparison possible (point and shoot cameras will change exposure if the light is dimmer or brighter which makes real comparison impossible). Since it's stopped down you'll only see light from the element, the reflector, and the lens, eliminating most of the aura and extraneous noises common to photos of bright lights at night.

    The lights I used were (both pretty much brand new):

    LED: http://www.superbrightleds.com/moreinfo ... b/170/767/
    Incandescent: http://www.autozone.com/autozone/parts/ ... fier=59020

    anyway, blah blah blah, I made the photos into gifs to make it even easier to compare. See for yourself:

    Bulb hi/lo comparison:


    LED hi/lo comparison:


    Bulb/LED lo comparison @ 0°:


    Bulb/LED lo comparison @40°:


    Bulb/LED hi comparison @ 0°:


    Bulb/LED hi comparison @40°:


    So it appears to me that for regular running lights, the LED outperforms the incandescent light significantly. BUT when braking, the incandescent goes brighter than LED.

    To me, both lights were plenty bright and it sort of comes down to taste. There wasn't much difference in terms of oblique visibility for the LED, so I wouldn't be concerned about LED lights being too directional. The LEDs do run cool, which really doesn't matter I guess, unless you're swapping out a hot incandescent bulb (like I did for this).

    I would say, if you want LED, then also go for a strobe module to maximize your visibility, that for me is enough to keep LED.

    This only compares this single LED bulb, and there are a bunch of others out there that I didn't test, so those results could be entirely different.

    In conclusion, I hope this is useful to someone…somewhere.

    Stay safe!
    Fredrick likes this.
    San Francisco, CA

    1978 Honda CB400
    1995 Ducati 900SS

  2. #2
    Super Moderator longdistancerider's Avatar
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    Re: Tail Light - LED vs Incandescent

    Very nicely written and illustrated. I think one of the differences that takes place is the LED's are projecting light were as the incandescent relies on the reflector to bounce light.

    Stickied
    dirceucorsetti likes this.
    Jim O'Brien
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    Member jbergen's Avatar
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    Re: Tail Light - LED vs Incandescent

    Also of interest is that the LED light throws quite a bit of light on the license plate and the ground which gives it a nice effect (IMO). I have some cell phone photos to show what that looks like

    LED


    Incandescent
    San Francisco, CA

    1978 Honda CB400
    1995 Ducati 900SS

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  5. #4
    Supporting Member Jeezus's Avatar
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    Re: Tail Light - LED vs Incandescent

    I used the same LED bulbs, and the light is great from behind the bike. There is more direct light, but the bulb puts out more ambient light, if that makes a difference.

    I think I will try these next:

    http://www.superbrightleds.com/moreinfo ... ower-/814/

    In the white LED style. I am sure the red LED would put out more visible light, but I am not sure if having red license plate light would be legal or not.
    1986 Honda CB450SC Nighthawk

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    Supporting Member ChileanIrishGuy's Avatar
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    Re: Tail Light - LED vs Incandescent

    Nicely done experiment - thanks! I may be wrong about this, but I don't think LEDs inherently blink at any particular rate. They're fast enough to turn on and off that perhaps they may visibly seem to fluctuate in a 60Hz household application, but I believe if they were being used with 50Hz power abroad, they'd then seem to blink slightly at 50Hz instead. With a well-regulated direct-current voltage, they shouldn't appear to blink at all, I'd imagine.

    I replaced the brake / tail light on my CM400C with a Jam Strait 1157 "super bright" red LED bulb and have been very happy with that switch. For me, it was mostly a matter of comparable (and possibly greater) brightness, with greater durability and reliability and lower power consumption. LED bulbs burn cooler because they use a small fraction of the current needed by a standard bulb (about 100mA or 0.1A vs. about 2A typically in the case of the 1157 bulb). While the engine is running and the battery is charging, this might not be noticeable. However, if one uses the "parking light" feature, one should be able to leave the motorcycle parked longer or just drain the battery much less with an LED tail light. Filaments in standard bulbs are also prone to getting brittle and breaking after enough heating and cooling cycles and sufficient vibration or agitation, whereas LED bulbs don't use a glowing filament and hence don't suffer from that eventual failure mechanism. By some estimates I've seen, LED lights can last about 25-50 times longer than incandescent bulbs. So I may never need to change my tail light bulb again unless it's physically destroyed (in which case, I'll likely need to change more than the bulb...).

    One last factor - LED bulbs reach full brightness faster than regular bulbs. Some people claim this translates into getting noticed faster from behind when braking, hence hopefully the car stopping a few feet earlier and farther from you and your bike. Drivers are so distracted today that they might not be so alert and responsive, but every safety advantage helps.

    I still haven't readily found LED alternatives for turn signal bulbs. Any recommendations?
    Anthony

    1981 CM400C "Camila"

    Give me a single sunrise over a lifetime of "reality" television anyday.

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  7. #6
    Member jbergen's Avatar
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    Re: Tail Light - LED vs Incandescent

    Quote Originally Posted by ChileanIrishGuy
    Nicely done experiment - thanks! I may be wrong about this, but I don't think LEDs inherently blink at any particular rate. They're fast enough to turn on and off that perhaps they may visibly seem to fluctuate in a 60Hz household application, but I believe if they were being used with 50Hz power abroad, they'd then seem to blink slightly at 50Hz instead. With a well-regulated direct-current voltage, they shouldn't appear to blink at all, I'd imagine.
    Nice and thanks!

    I guess to clarify, about the LEDs blinking: You're right that some LEDs are constant on and would not blink. But in my experience working with LEDs, the vast majority (all) have been driven at 60Hz while at full brightness **. I've designed and built a number of functional & interactive works featuring LED lights (solids as well as RGB), and I've found that most multi-state LED systems (a brake light would have two states-high & low) are achieved through a pulse width modulation chip that simply slows down or speeds up the flash rate (more Hz = brighter) regardless of the type of power source. But honestly I don't actually know what drives these bulbs, so to be on the cautious side I just made sure to account for the possibility.

    ** a simple experiment you can try to see this in action: Get a red LED bike light and turn it on in a darkened room. Set it to a setting where it's on but not flashing. Now quickly wave it it around in front of you (or have someone else do it for you). You most likely will see a minute strobe-like effect while the light is moving fast, but when moving slowly, or not at all, your persistence of vision fills in the gaps and it appears solid.
    MDM likes this.
    San Francisco, CA

    1978 Honda CB400
    1995 Ducati 900SS

  8. #7
    Supporting Member ChileanIrishGuy's Avatar
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    Re: Tail Light - LED vs Incandescent

    Now that you mention it, yes, seems like many LED applications use pulse-width modulation to regulate intensity and probably power consumption also. In some newer car lights, it's particularly noticeable.

    In any case, now I can have some empirical confidence that my LED tail light is usefully bright and that I'm not sacrificing performance for lower power, thanks to your experiment - most rigorous one I've seen, anyway! I especially liked the idea of using the DSLR at a uniform shutter speed as your "sensor." Thanks again for sharing results.
    Anthony

    1981 CM400C "Camila"

    Give me a single sunrise over a lifetime of "reality" television anyday.

    A little controlled insanity goes a long way toward preventing the onslaught of the Real Thing...

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