“If the first number in the optics formula (“8 X 42,” for example) is higher than 8, DON’T BUY IT.”
I’ll probably catch some hell for this one (and for at least some of the others) but do not buy a binocular stronger than 8 power—that is, if you want one that will give you the best image possible, be fun to use, and be something that you’ll continue to use down the road.
Above 8 power all the downsides of higher magnification start becoming more prominent, slowly eating away at the quality of your viewing experience and the likelihood you’ll keep bringing them along when you go out.
Generally speaking, with higher magnification binoculars the field of view will be narrower, the depth of field will be shallower, the image will be less bright (brightness goes down when power goes up) and less sharp (increasing the magnification of your hand tremor increases the subtle blurring of the image).
Obviously these statements are broad generalizations but their essential truth can be easily demonstrated by comparing 8 and 10 power binoculars with the same objective lens diameter (second number of the formula) by the same manufacturer—so everything is identical except for the magnification.
I’ve personally done this test many times, but more importantly I’ve encouraged countless customers who came to me saying they wanted a 10 power binocular to do the same test before they purchased (actually I kind of insisted on it).
I was blessed to have sold nature optics on a wildlife sanctuary, so I was able to construct the perfect optics test protocol: Take an 8-power and walk a trail for a while, looking at birds, leaves, berries, whatever one encounters on the trail. Then take the 10-power on the same trail and do the same thing. Once you’ve tried both, I would say, you’re free to buy whichever one you want.
In practically every instance the customer bought…the 8-power. No surprise.
(With the decline in the number of brick-and-motor stores with optics-knowledgeable staff, and the increasing popularity of online optics stores, in-person product demos and side-by-side comparisons like the one I just described are becoming, sadly, a thing of the past. Some online nature optics emporiums do go out of their way to help you, backing that up with liberal exchange/return policies—but there’s just is no substitute for hands-on tryouts for binoculars.)
Does all this mean that I dislike 10 power binoculars? No, I dislike 12 power binoculars, as well as the Voldermort of optics, the dreaded “15 power.” Yes, there’s a place for 10 power binoculars—that place is a hawkwatch platform like the Montclair Hawk Watch in Montclair NJ, or any of the other many hawk watch locations in the US and elsewhere. In fact a 10 power is often preferable whenever and wherever you’re looking at birds (or anything else) at long distances. Over the years when a few people have told me that ALL they do is watch hawks seasonally—a singular use for a versatile instrument I simply don’t understand---I just told them to go ahead and buy the 10X.
Another instance where you can justify the purchase of a 10X is if you are one of those people who are fortunate to be able to afford multiple binoculars, in which case a 10 power makes a perfectly acceptable second binocular.
So again, a 10X DOES have its place, but for your first or primary binocular, a 7X or 8X is the way to go. You don’t need a specialized glass for long-distance viewing, you want one that’s versatile, which is to say one that works well in all of the situations in which you would want a closer look.
And that’s every time you go outside, right?