With our annual Optics Fair coming up next weekend, I thought that this would be a good time to repeat my tutorial on the basics of binoculars and spotting scopes:
Binoculars have come a long way in recent years. Today’s optics are lighter, brighter, and sharper than the clunkers that your grandfather had You don’t have to spend a lot of money, but you pretty much get what you pay for with binoculars. There are some fine lower priced binoculars, and you can always graduate to better optics as your need or interest grows. Or, as most experts advise, you can invest a little more money now and buy the best binoculars that you can afford and they will bring you many years of enjoyment.
Most binoculars are labeled with their “size.” The 8-x-42mm or 10-x-42mm are the most popular for birding. Binoculars with magnification of 8 or 10 power, the first number that you see printed on the binocular, will bring birds (or any object) 8 or 10 times closer. Higher power may sound better, and it can be, but the higher the magnification, the harder it is to hold steady. If you can’t hold it steady, the blurred image is not an improvement. A lower power usually gives you a little more light, and a wider field of view. The wider the field of view, the easier it is to find a bird in a tree — because you are seeing more of the tree. Ten power does bring birds closer, but it the practical limit that experienced birders can hold steady without the aid of a tripod.
The second number (42 in the example above) is the diameter of the objective lens, the lens that is furthest away from you, in millimeters. The larger that lens, the more light that enters the binoculars. This matter most when light is less available, such as in the shade, on cloudy days, or at dawn or dusk. My first pair of binoculars were 7-x-50 — a little less power, but a larger objective lens that let in a lot of light. But the added weight of the 50 millimeter glass in the binoculars sure made my arms tired while watching those warblers in the tops of trees! Be careful of going to the other extreme with small compact binoculars, such as 8-x-20 or 10-x-25.