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Pair of 10x50 binoculars.
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Adjusting your binoculars
Before using a pair of binoculars, i.e. when trying them out in the shop or after buying them, you need to adjust them to your own eyesight. You do that by adjusting the diopter (which is different from the focus adjustment):
1. Hold the binoculars to your eyes, but look only through your left eye.
2. Choose an immobile subject, and adjust the focus (turn the focusing wheel) until the subject is as sharp as possible.
3. Now look through your right eye, and close your left eye.
4. Turn the diopter (usually by turning the right eyepiece or a wheel behind it) until the subject is sharp.
Now the binoculars are ready for use. From now on, you should leave the diopter alone. Only use the focusing wheel when you need to adjust the focus to see sharp.
  Glossary
Safari glossary
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Planning your safari:
Binoculars
If you were to choose between bringing a camera or a pair of binoculars (also known as field glasses) for a safari, the right choice would be the binoculars. With these you can spot and observe animals far away, and you will see and experience more during your safari. If you're interested in watching birds, you probably know already that a pair of binoculars is essential.

If you already own a pair of binoculars, you should bring them. If you don't own a pair, you should seriously consider buying one.

Binoculars vs. telescopes
A pair of binoculars, in which you use both eyes to look, is more useful than a telescope, in which you look with one eye only. Binoculars give you a three-dimensional view, and have a moderate magnification allowing you to hold them by hand. Telescopes give you no sense of depth, and most have a magnification too high; you shake the telescope too much and can't see properly.

If you can mount the telescope on a tripod or put it steadily on a bean bag, it may be a nice complement to the binoculars for looking at animals or birds at distance. Most safari-goers don't need a telescope, and if you don't already own one, don't buy one for the safari only.

Safari Patrol recommends:
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For general game viewing: 8x50 or 10x50 binoculars.
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For bird watching: 10x50 binoculars.

What does "8x50" etc mean?
In "8x50", the first number (8x) means that he binoculars magnify 8 times. The second number (50) is the size of the objective (the big lens that points towards the subject when you look through the binoculars) diameter in millimetres (50 mm=1.97 in). The larger objective diameter, the brighter image you get.

See Basic binocular and telescope theory below for more about what these numbers mean to performance.

Binoculars
There's a multitude of binoculars on the market, ranging from simple ones costing USD 20 to high quality ones (brands such as Swarovski, Leica and Zeiss) costing more than USD 2,000.

A good pair of binoculars doesn't have to bee a very expensive pair, but a pair you're happy with. Go to a shop, try some and compare. Can you adjust the diopter and focus to see well enough? Which ones feel the best to hold? Can you avoid shaking the binoculars?

And next, how much are you prepared to pay? Do you want a pair of binoculars that last for 15 years? Will you use them at all after the safari?

Full-size binoculars (8x50 and 10x50)
Full-size binoculars perform best, but are the heaviest. 8x50 or 10x50 means an all-round pair with enough magnification for normal game viewing, and good light sensitivity, meaning it can also be use in poor light, for example during dusk and dawn. For serious birding, you should have 10x50, or even a bigger pair.

Binoculars with a magnification higher than 10 may be difficult to hold without shaking. Try in the shop.

Compact binoculars
Compact or small binoculars are available in many different models, some of them really small and light. The size and weight is their main advantage.

Many compact binoculars have quite a strong magnification; 8x is not uncommon. Instead, the objective diameter is smaller, to diameters such as 32, 28 or 25 mm. This reduces the overall size and weight, at the cost of light sensitivity.

With a magnification of 8x, the light sensitivity decreases as soon as the objective diameter goes below 40 mm. At 10x, the decrease starts below 50 mm. A pair of 8x25 binoculars require close to full daylight to be of use.

You mainly use the binoculars in daylight on most safaris. If you accept that you may not use them very well at dusk and dawn, and that the image brightness is reduced, then you may be prepared to trade some performance for reduced weight. It may even be advisable to reduce the weight, if you also intend to bring equipment for photography or video filming.

For watching game at night around floodlit waterholes, you need as much light sensitivity as possible. 8x50 or even 7x50 is a good choice.

Sharing binoculars
The best is having a pair of binoculars for yourself. Then you can use it at any time, and you can have it properly adjusted to your eyesight.

A compromise is sharing with someone who has the same eyesight as you.

It's not good sharing with someone who has different eyesight, as one of you won't be able to see sharp images in the binoculars. This is because of the diopter setting, which you use for adjusting the binoculars to your eyesight. This adjustment should be done once only.

For information on how to do this adjustment, see Adjusting your binoculars in the left column.

Zoom
Binoculars with a zoom, i.e. adjustable magnification, may seem nice, but they offer less image quality and the mechanical parts usually make such binoculars short-lived.

Small 20–40X telescope.

Telescopes
Most telescopes have more magnification than binoculars, and require a stable mounting, such as a tripod. You can't keep it steady enough for a clear image by holding it by hand.

Telescopes are mainly of use when bird watching in lodge and camp areas, or when walking, if you can carry a tripod along. They may be of some use together with a bean bag in a vehicles, but tripods don't fit inside.

Telescopes don't have diopter settings, which means that they are not adjusted to the user's eyesight. Thus, they may be shared by more than one user.

Unless you already have a telescope, you shouldn't buy one for the safari only.

Lens coating
Light is reflected (i.e. lost) each time it passes through a lens surface. Coating the lenses during manufacturing reduces these reflections. A pair of binoculars without coating presents a darker image (because light is lost and never reaches your eyes), as well as a hazier image. The image in a pair with good coating appears bright and vivid and has good contrast. The more coating the better.

Tripods
Tripods can't be used in safari vehicles, as there isn't room enough between the seats, co-passengers etc. A bean bag is more useful in the vehicle.

A tripod may be used on lodges, camps and observation points, or during walks. It's one more thing to carry around, though, and on normal safaris, most safari-goers have no use of one.

Bean bag
A bean bag is a bag filled with beans (rice can be used, too), used as a stable support for a camera or telescope. On a safari, you may put the bag on the roof or in an open car window, and the telescope or camera on top.

You can device a simple bean bag yourself. Use a fabric bag, a big sock etc (anything goes, as long as it's not airtight), fill it with 1 kg/2 lb of beans, and tie it up with as string or strong rubber band. If you don't want to bring the extra weight on the flight to East Africa, you may bring an empty bag and buy beans or rice in a market after arriving, or even use sand to fill it.

Basic binocular and telescope theory
Two main performance factors of binoculars and telescopes are the magnification and the objective (or front lens) diameter. A pair of 8x50 binoculars, for example, has the magnification 8x, i.e. eight times, and the objective diameter 50 mm (1.97 in).

Magnification
The higher the magnification, the closer the subject seems when you watch it through the binoculars (or telescope). When watching an animal 50 meters away with a 10x binoculars, you see it as if it was 5 metres away.

In general, a higher magnification also means a narrower field of view. A narrow field of view usually makes it harder for you to orient yourself when looking through the binoculars (or telescope).

The higher the magnification, the less light sensitive the binoculars. Binoculars with high light sensitivity may be used in moonlight, while poor sensitivity may require full daylight.

Finally, not only the subject you're watching is magnified, but also any shaking from your hands. If magnification is too high, you may not be able to hold the binoculars steady enough to see a sharp picture.

Objective (or front lens) diameter
The objective or front lens is the big lens that points towards the subject when you look through the binoculars. The wider lens, the more light sensitive the binoculars (or telescope).

The wider objective, the wider the field of view. And the wider the objective, the heavier the binoculars.

Exit pupil
If you look into a pair of binoculars at arms distance, you see a small circle of light in each telescope. That's the exit pupil. The size of it determines how light sensitive the binoculars are; the larger the exit pupil, the more light passes the binoculars into your eyes, i.e. the more light sensitive the binoculars.

Your own pupils vary in size depending on whether it's light or dark around you. The size ranges from 2 mm/0.08 in (in bright light) to 5 mm/0.2 in (in complete darkness). If you are young, they may go as large as 7 mm/0.28 in in darkness.

If the exit pupil is smaller than your own pupil, less light reaches your eyes when you're looking through the binoculars than when you're looking without them. The result is an image darker than reality. If the exit pupil is much smaller than your own pupils, the image may get so dark you can't see anything at all in the binoculars.

Calculating the light sensitivity
You may calculate the size of the exit pupil by dividing the objective (or front lens) diameter by the magnification. A pair of 8x50 binoculars has the exit pupil 50/8=6,2 mm (or 1.97/8=0.25 in. That's larger than the maximum pupil size for most adults (5 mm/0.2 in), which means good light sensitivity.

A pair of 10x28 compact binoculars has the exit pupil 28/10=2,8 mm (or 1.1/10=0.11 in), which is far from light sensitive. Such a pair can mainly be used in good daylight only.

To use a pair of binoculars in twilight, it's exit pupil should be at least 5 mm/0.2 in. For 10x magnification, for example, you need at least a 50 mm/2 in objective. So what you want is: 6x30, 7x35, 8x40, 10x50 or 12x60.

 
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Page updated17 February 2009