I think the big thing when buying binoculars is to ask yourself "what do I want them for?" Are they for all-around use or for specialized use? For example, if they are primarily for hiking/backpacking, lightweight ones tend to be the way to go. If they are for astronomical use, quality of the optics is by far the most important factor.
For hiking/backpacking, I have an old pair of Empire 7x35mm binos with an extra wide field (over ten degrees!). These are extremely lightweight and the wide field is great for checking out terrain features, birds, etc..
For astronomy, I use a pair of Celestron "Ultima" series 7x50mm binos. These are of excellant optical quality. They use the BAK-4 prisms, which are better than the BAK-7 prisms used in most department store models. They also have fully multi-coated lenses. This is also very important to maximize light transmission. Some binos have no coatings at all (they usually look white if you turn them around and peer into the objective lenses) or advertise "coated optics" or "multi coated optics." In some cases, only the exterior objective lenses are coated. In "fully multi-coated" lenses, EVERY air-to-glass surface is coated. These generally appear greenish when you peer into the objectives. Some manufacturers advertise "ruby" coatings and the lenses look reddish or pinkish. Thses are of no use at all and are often worse than no coatings! It is a marketing scam. When you look at binos and they are the same magnification/aperture and there is a big price difference, check out the prisms and the coatings. This is where manufacturers skimp if they want to make them cheaper in price. These factors are most important in astronomical binos.
There are giant binos of 11x80, 20x80, and even 25x100 (the last ones running near a thousand dollars). These all require a tripod to use because the strain on your arms is almost immediately apparent. The images dance around while you are trying to see. With 10x50mm and smaller, weight is generally not a problem.
Always test the binos you are considering or make sure that they have a 100% money-back guarantee. This way, if they are not up to par you can return them. Don't necessarily think that the name brands are always the best. I have found some name brand ones of mediocre quality and some lesser known brands of outstanding quality. My 11x80mm binos are made by Orion (the astronomy company). They are probably actually made at the same plant as one of the big names, but are marketed as Orion's brand. The Fujinons are almost always of excellant quality, and I have Celestrons that I wouldn't trade for the world. If you are testing them in a store, make sure you see exactly the same details in both eyes as you look through them. Looking at a brick wall or ceiling tiles from a distance is good because you can compare the views easier. If the images in each eyepiece are not identical, the tubes are slightly out of alignment and they are no good. They will produce distorted images and limit your ability to discern fine detail. Also, if you think you might want to use them with a tripod for nature watching or astronomy, make sure they have a tripod adapter hole. This allows you to screw the adapter into place and mount it on a photo tripod. If they are to be used in the woods, waterproof models and those with rubber or "armored" bodies may be the way to go. This will protect them against moisture and help them resist damage if dropped from a deer stand or boat. ALWAYS use the neck strap. Most come with the little thin ones that dig into your neck after a few minutes, but you can replace these with the wider ones for about $5.00. Celestron's better models all come with the wide strap. If you want to buy one separately, go to
www.telescope.com and check out their binocular accessories. They sell them. They really are a big improvement over the thin ones.
About the magnification and aperture. The higher the magnification, the smaller the field of view (in general). This is because as the magnification increases, it becomes more difficult to prevent distortion at the edges of the lenses. So, they cut the field size down to eliminate it. If you see some advertised as having really wide fields (over 8 degrees or so), be sure to look at the edges of the field when you are testing them to make sure their isn't a lot of distortion. In general, 7 power binos will average about a 7 degree field of view, with some going up to ten degrees. These ten degree ones usually have distortion. 10 power models average from 5-7 degree fields of view, and the giants get around 2-2.5 degree fields. The field of view is important for astronomy or bird-watching, since a larger field helps you acquire your target faster and easier.
For astronomical use, the magnification and objective diameter work together to tell you the exit pupil. The human eye, when fully dark-adapted, has an average exit pupil of 7mm or so. This is in someone young. It decreases with age to about 4 or 5mm. In the daytime, the exit pupil is much smaller. This is why your pupils look so much larger when you come in from a dark area into a lighted one. If you live under really dark country skies, you can take advantage of this night exit pupil by getting binos that have a matching exit pupil. For instance, 7x35mm binos have an exit pupil of 5mm (35mm objectives divided by the 7 power equals 5mm exit pupil). 7x50mm ones have an exit pupil of 7mm, exactly the same as the dark-adapted human eye of a person under 40 or so who doesn't smoke (smoking reduces your night vision capability). These are better for astronomical purposes under dark skies because they allow your eyes to see everything the binos are capable of revealing. 10x50mm ones have a 5mm exit pupil (50mm divided by 10 power equals 5mm exit pupil). They don't allow your eyes to see to their maximum ability but compensate for it by giving you a magnification of 10 instead of only 7. This whole issue is really only relevant for astronomy and lookouts on ships. The Navy uses 7x50mm binoculars for just this reason.
My personal opinion is that for home use, a pair of decent 10x50mm ones are the way to go. For hiking/backpacking, go with the lighter/waterproof models, maybe 7x35mm with a wide field. For astronomical use, go for optical quality: fully multi-coated lenses and BAK-4 prisms. Also, I always get the models that allow you to individually focus each eyepiece. Some have ONLY a center focus and this does not allow the binoculars to compensate for the different vision in your eyes if they are not 20/20. The individual focus ones do. Most have an individual focus for the right eye. Then after it is focused to match the left eye, you use the center focus to bring them both to a sharp image. These are fine for all purposes. If you wear glasses, consider getting those that have the rubber eyeguards that can fold down or be removed. This way you will have comfortable eye relief even with your glasses on.
My recommendations? I have and like the Celestron "Ultima" series, the Fujinons (though they often weigh much more than the others of the same specs), the Orion "Giant" series (I have never used their smaller models), and I have a pair of Sears 10x50mm binoculars that work like a charm for everyday use. They are waterproof and have rubber-coated bodies to resist shock if dropped. I have replaced the thin neck strap with a thick one on all of my binos.
I hope this long post helps out some! See ya later. JRF.
[This message has been edited by jrf (edited 01-27-2000).]
