Biology Reference
In-Depth Information
cups if you don't wear eyeglasses. Since eyeglasses hold binoculars away from the eyes
and let in peripheral light anyway, retract the eyecups if you do wear glasses.
Next, set the barrels of the binoculars to match the distance between your eyes. Look-
ingthroughthem,adjustthebarrelsuntilyouhaveasolidimagethroughbotheyes.Ifthe
width isn't set properly, your image will black out.
Virtually all binoculars on the market have center focusing, in which a single knob or
lever controls thefocusforbotheyepieces simultaneously.Oureyesareseldom precisely
matched, so to accommodate the difference between our two eyes, binoculars also have a
diopter adjustment near the optical lens on one side or the other, or as part of the center
focus knob. Diopter adjustments are normally numbered from +2 to -2.
Here's how to adjust your binoculars so you can use them without eyestrain:
First find the diopter adjustment and set it at zero.
Find something a good distance away that has clean lines. A sign or something else
with letters or numbers is often a good choice.
Cover the objective lens (the large outside lens of the binoculars) with the lens cap or
your hand on the side controlled by the diopter adjustment, and then focus on the sign
using the center focus knob. Try to keep both eyes open as you do this.
Switch hands, uncovering the lens with the diopter adjustment and covering the other
lens. Focus again, this time using the diopter adjustment, not the center focus.
Repeat each adjustment a couple of times. After you're done, your sign should be
crisply focused through both eyes.
Notice the number setting on the diopter adjustment. Sometimes during normal use,
the adjustment knob may get shifted, so every now and then, check to make sure it's
set where it should be for your eyes.
Finally, make the neck strap as short as it can be while still allowing you to use the
binoculars comfortably and put them over your head easily. The longer the strap is,
the more the binoculars will bounce, and the greater the chance you may bonk them
against rocks, tables, and other objects whenever you bend down.
Q I think I have my binoculars perfectly set for my eyes, but I just can't find any
birds with them! There can be a cardinal sitting in a tree right in front of me, but
when I pull up the binoculars and try to scan, the bird flies away before I can find
it. What should I do?
A
When you find a bird, keep your eyes on it while you place the binoculars in front of
your eyes and focus without moving your head. Practice this with inanimate objects first.
Starting with large items, test yourself to see how quickly you can spot something and
