Ryan Christiansen wrote:
I've been spending some time paddling in the national wildlife refuges
in North Dakota and I've come to realize that I need a good set of
binoculars. They should be waterproof and not too expensive. I've
looked around and there are way too many to choose from.

A few things to consider to narrow the choices. First, how much
magnification would you like? This depends on how you plan to use them.
Handholding binoculars above about 8x becomes difficult, especially if
you're doing it from an unstable platform like a canoe or kayak. OTOH, if
you'll be using them on a tripod to spot birds at long distances then you
may want to go up to 20x or so. For handheld use I'd stay in the 6 - 8x
range and decide within that based on how steady your hands are.

Second is the light-gathering power. The size of the light beam leaving
the eyepiece of the binoculars is determined by the size of the objective
lens divided by the magnification. So 7 x 50 binoculars (7 power, 50 mm
objectives) will have an 'exit pupil' of 7.1 mm. If this is larger than
the pupil of your eye then some of the light falls outside your eye and is
wasted - doesn't hurt the view, but you're carrying around bigger, heavier,
and more expensive binoculars for no improvement in the usable light. The
average fully-dilated pupil for young adults in very dark conditions is
about 7 mm, but this decreases with age and will also be smaller if it's
not completely dark. So if your eye's pupils are only 5 mm then you'll get
just as bright and clear a view with 7 x 35 binocs as with the bigger and
heavier 7 x 50s. In the daytime your pupil size will probably be 3 mm or
less and you can see just as well with much smaller binoculars (7 x 21 or 8
x 24) under these conditions.
Determine what lighting conditions you'll be using them in and either
measure or estimate your pupil size under those conditions.

Third is to consider size and weight. Even if you'll be using them under
dark skies and your pupils open up to a full 7 mm, you may prefer to carry
something the size of 8 x 40s rather than 8 x 56. The bulk and weight of
binoculars goes up rapidly with the objective diameter (the second number
in their specification).