INSTRUMENTS
Key Points to keep in mind:
Magnification:
The
higher
the magnification,
the
bigger
the
increase
in
apparent
size
of
a
given object.
For example,
an
object
1,000
meters
away
when
viewed
with
lox
binoculars
appears
only
100
meters away,
or
10
times
larger
than
with
the
naked eye.
Higher
magnification
does
not
necessarily
mean better.
If
the
magnification
is
too high,
the
object
does
not
appear
clearly
due
to
binocular
shake (caused
by
a
slight
trembling
of
the
hands.) Generally,
binocular
shake
is
not
a
problem
with
magnifications
of
up
to
8x.
You
can
also
use
binoculars
with
a
12x
magnification
without
binocular
shake
once
you
become
familiar
with them.
 |
Generally,
the
higher
the magnification,
the
narrower
the
real
field
of view,
and
the
lower
the brightness.
Take
7x35
and
10x35
binoculars (both
featuring
objective
lenses
with
the
same
effective diameter)for example.
Although
the
object
appears
bigger
when
looked
at
through
the
10x35
binoculars
than
through
the
7x35
model,
the
lower
magnification
model
offers
a
much
brighter
image
and
a
wider
real
field
of view.
It
is
therefore
important
to
choose
binoculars
with
an
appropriate magnification. |
Field of view:
Real
field
of view:
As
shown
in
the
figure below,
the
real
field
of
view
is
the
angle
of
the
visible
field
measured
from
the
central
point
of
the
objective lenses.
The
bigger
the
value,
the
wider
the
field
of view,
and
the
easier
it
is
to
locate
the object.
(Note
that
some
binoculars
from
other
manufacturers
have
excessively
widened
fields
of view,
which
produce
a
distorted
image
around
the edge.)
The
wider
the
field
of
view
the
better
for
watching
moving
or
large-scale objects.
Apparent field of view:
The
apparent
field
of
view
is
the
visible
breadth
as ,seen
through
the binoculars.
It
is
obtained
by
multiplying
the
real
field
of
view
by
the magnification.
For example,
in
case
of
the
7x35
8.3
"binoculars:
Real
field
of view:
8.3"
Apparent
field
of view:
8.3
°
(real
field
of view)
x
7 (magnification)
=
58.
1'
Wide
field
of view:
Binoculars
with
an
apparent
field
of
view
greater
than
65
° are
defined
as
wide
field-of-view
types
according
to
the
Japanese
Industrial
Standard (JIS),
These
binoculars
are
designed
to
maintain
a
wide
real
field
of
view
even
at
a
high magnification.
Several
wide
field
binocular
models
are
available
from good quality.
|
 |
Eyepoint
and
eye
relief:
Eye
relief
is
the
distance
between
the
eyepiece
and
the eyepoint.
|
Eyecup
folded |
Eyecup
unaided |
|
When
you
place
your
eye
correctly
at
the eyepoint,
you
can
see
the
whole
field
of
view
without
any shading.
If
the
eye
relief
is
too
short,
you
cannot
place
your
eye
at
the
eyepoint
and
the
field
of
view
is
partially
shaded
off.
High
eyepoint
binoculars
with
longer
eye
relief
(15mm
or
longer)
are
recommended
for
eyeglass wearers. |
French