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 PART
I
Why
get pocket optics? The
best binoculars in the world are useless if you don't have
them with you.
You
know the story. You left them home because they were too
heavy and you weren't intending to go birding anyway.
But birds
can turn up anywhere, any time. A black-throated blue warbler
might materialize in the mall's parking-lot shrubbery. Or
a tufted duck could wander in from Europe and light on the
river you drive across every day on the way to work.
What
if there were a binocular so small and light that you always
had it with you? Something that would take up almost no room
in your purse or pocket but still had excellent optics and
rugged construction, like the Leica 8x20s shown at right?
You would always be ready and never miss a bird.
Sound
good? Then welcome to the world of pocket optics.
For a
review in
Bird Watcher's Digest, Michael and Diane Porter
collected 40 pocket binoculars from 17 manufacturers and assembled
a team of southeast Iowa birders to try them out. We limited
the entrants to those weighing less than 13 ounces. The lightest
was only 5-1/4 ounces. All might fit into some sort of pocket
and could properly be called pocket binoculars, and a few
can actually be carried in a shirt pocket. None of the binoculars
we tested was over 4-1/2 inches long. They fell into two groups,
roof-prism design and reverse Porro-prism design.
Advantages
of pocket binoculars
The smallest
binoculars we tested were all roof prism design, in which
the front lenses and the eyepieces are in a straight line.
Roof prism binoculars are naturally compact. And furthermore,
most of the pocket roofs can fold even smaller when not in
use. The Porro prism group averaged somewhat larger. Although
regular Porro prism binoculars have an obvious zigzag shape,
with the front lenses wider apart than the eyepieces, reverse
Porros have the front lenses closer together than the eyepieces.
This allows for a more compact package.
Limitations
of pocket binoculars
Are there
tradeoffs for pocket convenience? Does everything look smaller?
No, pocket binoculars can magnify the bird just as much as
full-sized models. And the image can be just as sharp and
clear.
 However,
there are some limitations. Their small objective lenses,
usually only 20 to 25 millimeters in diameter (like in the
tiny Pentax DCF MC 8x22, on top), cannot deliver as bright
an image in dim light as can binoculars with 42mm objectives
(like the full-sized Pentax DCF WP 8x42, on the bottom). But
in ordinary daylight, assuming they have good optics and lens
coatings, pocket binoculars will seem just as bright as their
larger cousins.
The field
of view is often narrower, but not always. Field of view is
actually related not to size, but to eyepiece design. For
example the Pentax DCF binoculars offer a 330-foot field of
view at 1,000 yards both with the standard-size 8x42 model
and with the pocket 8x22 model.
PART
II Features
to look for in pocket binoculars
PART
III The Reviews
PART
IV Chart of pocket optics
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