The ideal binoculars are ones that make you forget you are
looking through binoculars. If you purchase a pair with a wide
field of view, and the image quality is superior (enough that
there isn't much difference from looking with the naked eye),
you will have many enjoyable hours of use. Some people have
the misconception that because they only concentrate on the
middle of the lens, even if the outer part is blurred, it really will
not matter. Normally, the retina projects aberration-free images,
so when you view blurred images, the brain tries to disregard
them. If you consciously try to reject the blurred images for
a long period of time, there is a chance that you will become
very tired and even sick. It is very hard to determine the image
quality with just a spec sheet. The easiest and surest way is to
actually look through the binoculars. Please keep the following
points in mind when purchasing binoculars.
1) Do you see only one image or two?
Binoculars use two lenses parallel to each other. However, if
alignment during manufacture is not perfect, or owing to shock
during transport, the lenses may become just a bit off. If that
happens, you will see two images. Even if you get the binoculars
fixed, the lenses will tend to slip with just a slight jolt. Such
binoculars are not recommended.
2) Is the image sharp enough?
Make sure that the lettering on a sign or the thin branches
on trees are crystal clear (See comparative photos "Resolving
Power" on page 7). Also, make sure that the lights at night
and the stars are not blurred and the shapes are not distorted
(photo a). It may be difficult to know how clear the image is
by looking through only one pair of binoculars. Try looking
through several, and you will be able to tell the difference.