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8×42: The most Versatile Binocular
If you’re looking for a pair of binoculars you can use everywhere, an 8×42 should be your choice, since they are the ones you can use for virtually anything you might be interested looking at through your binoculars and in any circumstances – all-purpose, all-terrain binoculars. As far as size is concerned, they are right between the two extremes: pocket binoculars and giant binoculars. The biggest advantage of this category of binoculars has to do with the special combination of magnification and the size of the big lenses at the front, the objective lenses.
What should the diameter of the objective lenses be for versatile binoculars? The choice is determined by two factors: What the objective lenses are for and how much the instrument will weigh.
The big lenses at the front are for gathering light, without which no image will ever reach the viewer’s eyes. Bigger lenses gather more light, but bigger lenses weigh more and this means the instrument will be heavier and more bulky. Smaller lenses are not that heavy, but on the downside, let less light enter the instrument. So manufacturers have looked for a golden mean between enough light gathering ability and not too much weight for an all-terrain binocular and the result is a binocular with objective lenses of 42 mm.: They feed in lots of light in bright daylight and are effective enough for reasonable viewing in low light conditions, but are small enough to ensure that the instrument is not too heavy or bulky.
What should the magnification power of an all-purpose binocular be? The power available in ordinary binoculars vary from as low as 6x (some cases even 4x) to 12x; beyond that you move into the realm of giant binoculars. Some binoculars with 8.5x and 10.5x magnification are also on the market. Power of 9x is associated only with big lenses of 63 mm.
6x magnification power is too low and 7x is better, but still marginally below par for an all-terrain pair of binoculars. On the other hand, higher magnification like 10x and 12x has certain implications: It will be a luxury to have more magnification at your disposal, but the image will not be as bright. Furthermore, higher magnification is also associated with sensitivity to any kind of movement. The slightest movement, like normal hand tremors is amplified making finding an object (in particular when it’s moving) very tough. High magnification also causes a narrower field of view, which in combination with the problem of movement sensitivity, makes focusing on an object even more difficult. It also causes flatter depth of vision, so the viewer has to keep his finger on the focus wheel in particular if the objects moves towards him or further away. For this reason watching birds quite close is difficult with a powerful binocular.
Considering the pros and cons of different magnifications, it has become clear that the best magnification power for a versatile binocular is 8x. It is powerful enough to make you see distant objects and to see a lot of detail the closer the object gets. 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 viewer’s eyes on the other side of the binocular. An 8×42 gives you an exit pupil of 42/8 = 5.25 mm. With the same apertures (42 mm.) a 10x magnification gives you an exit pupil of 4.2 and a 12x magnification 3.5 mm. Exit pupils this small will be quite sufficient when the sun is shining, but when the sun is not shining and conditions are dim the smaller exit pupils will let too little light through for you to see a clear image.
Optical glass and coatings
The best compromise for an all-purpose binocular (8×42) will not ensure good images; the quality of the optical glass and prisms, as well as the optical coatings, play the decisive role.
About the Author
The author has written extensively on binoculars and is the owner of binocularsreviewed.net and pocketbinoculars.net.
My Choice of Binoculars..SHTF..10×25 Tasco..Light Wght. Powerful, Great Price
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