Scopes and optics

Subject: Scopes and optics
From: <>
Date: Thu, 21 Mar 2002 0:28:47 +1100
A 77mm objective lens has around 65% larger light gathering area than a 60mm 
lens (77^2 / 60^2 = 1.6469444...)  However, the human retina has a non-linear 
response to light, so 65% more light does not mean a 65% "brighter" image - 
particularly since the human eye has it's own auto-exposure system (i.e. the 

Where the objective lens size does make a difference is in at the extremes of 
the eye's capability.  A large objective lens may produce
an image too bright for the human eye in strong lighting conditions, but also 
produces a brighter image in dull lighting conditions (which is arguably the 
more likely scenario.)

Naturally, there is a weight penalty with larger scopes that should not be 
underestimated - a 50mm scope that you can happily carry everywhere will 
outperform the 83mm cumbersome giant left at home because you "didn't need it" 
- and of course did.

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