Or do they?
Several years ago I bumped into M in Central Park. I was sporting a brand new pair of (what was then) state-of-the-art 8.5x42 binoculars which M was eager to test. She was in the market for a new pair and was in a quandry about what to buy. A week later I saw her in the Park again. She was proudly sporting a new pair of 10x42s. They were the same model I showed her the previous week, but they were 10s instead of 8.5s.
Throughout our morning bird walk, she kept complaining about not being able to find birds. I explained that her 10s had a much narrower field of view (325 feet at 1,000 yards) than the 8.5s (390 feet at 1,000 yards) she saw the previous week. I told M that she would get more pleasure from the lower power model and suggested that she exchange them. But many of her celebrity birder friends used 10s and she kept hers, and complained about them for the next five years. She often just left her 10s home and borrowed binoculars from me until she finally bought a new pair of 7x42s just a few weeks ago. How do birders spell relief? 鈥淪-E-V-E-N.鈥
I get lots of requests for advice about which binoculars to buy, and I always suggest models which magnify the image by 7 or 8 times. More often than not, people argue with me. 鈥淚 want 10s.鈥 鈥淢ore power must be better.鈥 Buying lower power binoculars seems to many people to be, well, unmanly. Undignified. Unbecoming of a serious birder.
The fact is that binoculars with lower magnification will be brighter and offer a much wider field of view than their higher power cousins. They will also be easier to use, less tiring, and will provide more useful information. For those aging baby boomers among us whose hands shake more than they used to, they are essential.
Field of view is extremely important because a wide field makes it easier to find a bird and keep it in your binocular as the bird moves around. Think of your binocular tube, for a moment, as a very expensive toilet paper roll. Go get a real toilet paper roll and try finding a bird by looking through the tube. It鈥檚 almost impossible. If you manage to find a bird you won鈥檛 be able to keep it in sight when it moves. Now, cut the roll in half and try again. Much easier. Now, cut it in half again. Much easier again. Each time you cut the roll in half you are widening the field of view. If you are still not convinced, go to YouTube and watch 鈥.鈥 It鈥檚 a Japanese comedy skit in which a bunch of soccer players try to play with binoculars strapped to their heads. None of them can find the ball (or each other) even though it is right at their feet.
What about brightness? A lower power binocular will be brighter (all other things being equal) than a higher power model. A bright image shows more detail, more subtlety of color, and is more pleasing to use than one that isn鈥檛 as bright.
My final point is that lower power binoculars provide more useful information. Remember that a binocular which magnifies an image 10 times also magnifies the small movements of your hand 10 times. Even the steadiest hands have some movement. Even if those micro-tremors aren鈥檛 obvious to you, they will make your eyes tired and you won鈥檛 know why, because your brain must work to compensate for your hand movements. A 7 power binocular will be more comfortable and less tiring to use for a full day of birding. Although this seems counter-intuitive, 7 power binoculars will give you more detail than 10s.
If you are not convinced try the following experiment. Tape a dollar bill to a wall in a sunny place with the back of the bill showing (the back is the side with the written 鈥渙ne鈥 in the middle). Below the letters of the 鈥渙ne鈥 there appears to be a shadow. If you look very closely you will see that the shadow is really made up of very fine lines.
Now take a pair of 10 power binoculars and mount them on a tripod and focus on the dollar bill at a distance of 10 feet. Be sure that you can distinguish the lines below the 鈥渙ne.鈥 Now move the tripod back, a few feet at a time, until you can no longer distinguish the separate lines. The next step is to repeat the experiment with a pair of 7 power binoculars. You will not be surprised to find that the 10s offer superior resolution.
Now repeat the same experiment while holding the binoculars in your hand rather than mounting them on a tripod. This time the 7s will always win. It鈥檚 like a digital camera with an electronic image stabilizer. You get a much sharper image by minimizing movement.
What do I carry? My standard birding binocular is a 7x42. What did Roger Tory Peterson use while he was working on his last revision of his field guide? He used a pair of Zeiss 7x42s. Which binoculars did David Sibley use while he was working on the Sibley Guide to the Birds? You guessed it. Zeiss 7x42.
My never-leave-home-without-them binocular is a tiny pair of Leupold 6x32s. I find that in the real world, the difference between an image which is magnified by 6 or 7 times is not as different from one magnified by 10 times as you would imagine. The payoff for downsizing is a brighter image, a wider field of view, and an instrument which is less tiring and more pleasant to use.