42lm for a turn signal housing?

1-3-2-4

Newly Enlightened
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Nov 22, 2008
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72
is 42lm bright enough to still be seen during daylight hours? I have a 60 LED SMT bulb im not too pleased with and was curious.
 

-Virgil-

Flashaholic
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Mar 26, 2004
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Not even close. In North America, front turn signals are required to emit at least 200 candela on axis, and that's just for the lowest-output class of front turn signal, mounted at least 10cm away from the axis of the low beam headlamp. The light sources used to attain this performance typically emit around 400 lumens.
 

-Virgil-

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Mar 26, 2004
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About 400 for a white light source. About 302 for an amber light source.
 

2xTrinity

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Dec 10, 2006
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Is this 400 lumens from a white or amber source?
I have a different approach -- we can estimate the total number of out the front lumens required with a few assumptions.

Lumens are defined as candela times the solid angle into which that intensity is projected. A light source emitting 1 candela equally in all directions (eg into an entire sphere) will be 4pi lumens. A light source emitting 1 candela uniformly into a hemisphere will be 2pi lumens.

Maximum required intensity on-axis 200 candela. Let's say that "on average", we need intensity to be half of peak, or 100 candela, and we need that intensity to be emitted into a "quarter"-sphere. That's about ~100pi, or ~300 lumens out the front.

That's a lot of assumptions, could be anywhere from 100 - 400 out the front lumens, but I can safely say 42 gross lumens won't be enough if we need >100 out the front.
 
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