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binoc recommendations



The eye relief is, as was pointed out, is important.  As is the alignment 
issue.

The other important consideration is the size of the exit pupil.  Divide 
the objective size by the magnification to obtain the exit pupil e.g. 42 
mm/ 8 power = 7mm  The exit pupil is the size of the spot of light that 
enters you eye.  Your pupil can dilate to about 7 mm.   The 10 X 21 Nikons 
that were recommended give a maximum exit pupil of 2.1 mm so they will be 
fine in bright sunlight, but somewhat limited at dawn, dusk, or cloudy 
conditions.  You will still see the bird, but lose detail and color.


Ever wonder why birding standard binocs are 7X35, 8X40 (or 42 rather than 
40) -- its that old 7 mm exit pupil thing.  The higher price and higher 
power 10x40 are a compromise in exit pupil which is compensated for by the 
magnification, and the quality of the optics.


Lets now talk about close focus.  Do you ever look at butterflies?

Tom

Tom Krakauer
Bahama, NC
tkrakauer@mindspring.com