Amber Apparent Brightness Question

[beezaur]

I am making a decision on one of two LED lights for my bicycle, both amber LED. One is 400 lumens, the other 150 lumens.

But . . . am I correct that the human eyeball is more or less logarithmic in its sensitivity to light? That would mean the dimmer is. . .

log(150) / log(400) = 84%

as bright as the brighter one, to the human eyeball.

Is that right? Is there a wavelength-specific aspect for an amber LED?

 

[SemiMan]

Actually the ratio would be approximately = 400^0.5/150^0.5 = 60% perceived brightness increase. The 0.5 value is generally recognized for a point source and bright lights but it is not an exact value either.

Semiman

 

[beezaur]

For neurologic response?

I need to know more about this. Any pointers to references?

 

[alpg88]

with white light 3x in lumens looks like 2x increase in brightness, not sure it that could be applied to amber.

 

[SemiMan]

Steven's power law. Far from an exact figure, and there are others out there that are just as accurate or not.

Semiman

 

[beezaur]

Thank you!

 

[SemiMan]

Any time ... Reasonable wikipedia info on it. What can be missed is that perceived brightness and "usability" are not the same. 2x the lumens may only seem somewhat brighter but with the same led and reflector it is 40% more throw.