The Best All-purpose Binocular: 8x42

The Best All-purpose Binocular: 8x42

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If youre looking for a pair of binoculars you can use everywhere, an 8x42 should be your choice, as they are the true all-purpose binoculars, suited for any application. They are bigger than the really small and compact ones, but smaller than the really outsize binoculars. Size is just one of the in-between features; more important are the power and apertures.

How big should the apertures be for a versatile pair of binoculars? The decision is based on two cardinal issues: The function of the objective lenses and the weight of the binocular.
The purpose of objective lenses is to gather light, without which no image will ever reach the viewers eyes. Bigger lenses gather more light, but bigger lenses weigh more and this implies a bigger and heavier binocular. Smaller lenses are not that heavy, but unfortunately let less light enter the instrument. The challenge has always been to make a binocular which gathers enough light, but does not weigh too much for a versatile binocular and objective lens diameter of 42 mm. is just that: They feed in lots of light in bright daylight and let enough light through for reasonable viewing in low light conditions, but have only a moderate effect on the overall weight of the instrument.

What should the magnification power of an all-purpose binocular be?
The following magnification is available in ordinary binoculars: 6x, 8x, 10x and 12x; more magnification power is associated with big and heavy binoculars for which tripods are needed. You do get some in-betweens as well, like 8.5 and 10.5. Power of 9x is associated only with big lenses of 63 mm.

Magnification of 6x is a bit too weak and 7x is better, but still not powerful enough for an all-terrain pair of binoculars. On the other hand, more powerful magnification like 10x and 12x comes at a price: You will have the joy of more magnifying power, but the image will not be as bright. Furthermore, more magnifying power is also associated with amplification of movement. The slightest motion, like binoculars shakes is amplified making finding an object (in particular when its moving) very tough. More power inevitably means a smaller field of vision, which in combination with the problem of movement sensitivity, makes focusing on an object even more difficult. The depth of vision of the instrument is also impaired, which means that the viewer has to adjust the focus more often. For this reason watching birds quite close is difficult with a powerful binocular.

Clearly the golden mean as far as magnification is concerned, is 8x. It is powerful enough to make you see distant objects and to see enough detail at any range. However, 8x is not too powerful to let you suffer from the negative features associated with high magnification mentioned above.

Exit pupil
The exit pupil is the stream of light arriving at the viewers eyes on the other side of the binocular. The exit pupil is determined by dividing the objective lens diameter by the magnification: 42/8 = 5.25 mm. So it follows that the exit pupil of a 10x42 is 4.2 mm. and 3.5 mm. in the case of a 12x42. Exit pupils this small will be quite sufficient when the sun is shining, but when the sun is fading, in overcast conditions or in a darker environment like a forest the smaller exit pupils will let too little light through for clear images considering the amount of light available.

Optical glass and coatings
The best compromise for an all-purpose binocular (8x42) will not guarantee excellent viewing; the glass used for the lenses and prisms as well as the optical coatings have to be of the highest quality.

About the Author:
The author has written extensively on binoculars and is the owner of binocularsreviewed.net and
www.pocketbinoculars.net.



Article Originally Published On: http://www.articlesnatch.com


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