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Old 06-28-2010, 12:17 PM
CalMeacham CalMeacham is offline
Join Date: May 2000
Location: Massachusetts
Posts: 42,037
The human eye exhibits a fairly large chromatic aberration, meaning that when red is in focus, blue is out of focus. This might help to explain why blue is harder to resolve
Much more significant to the OP, you don't have the retinal ability to resolve blue very well. It isn't the sensitivity, it's the density of blue receptors or how they are wired.

I don't believe these are correct -- if you only have blue LEDs in your field of view, you're going to be trying to focus on blue, and not on other colors, so the chromatic aberration is beside the point.

And the "density of blue receptors and how they are wired" is what determines the sensitivity to blue, so the sensitivity is the point. Look at the plot of sensitivity on the page I link to -- it's way down for blue, which is why you have a harder time seeing it. In a similar way, the sensitivity id greater=st for green, and if you look at greed and red laser pointers of the same output the green one looks much brighter. This is entirely a function of the sensitivity.