Bike light brightness question?

[Fordulike]

I have two single Cree torch type lights mounted on my handlebars, both concentrating the beam into one single spot.

I don't know how many lumens they produce, but let's say they are 100 lumens each.
Do two lights concentrating the beam into one spot, equal one light producing the same amount of total lumens, or does it not work that way?

Example:

2 x 100 lumen lights in one spot = 1 x 200 lumen light

 

[Wicky]

Ask the RAF ;-)

 

[flecc]

Yes, lumens are additive, but not to the eye. Our eyes are logarithmic so to get double the perceived brightness requires a huge increase in the number of lumens. For the same reason we can only just see the output of a 200 lumen light as more than that of a 100 lumen light.
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