The winning squad in last year’s World Series of Birding, an annual competition in which more than 50 teams vie to spot the most bird species in 24 hours, admits that it had an edge: killer binoculars. “Our Swarovski binoculars are very good at light gathering, so after dark we can scan for owls on snags,” says Jeff Wells, a member of the Cornell ornithological lab team. Whether you want to discern barn swallows from cliff swallows, laser in on the line of scrimmage, or scan the horizon for other boaters, with binoculars, light gathering is the name of the game.
The key to collecting more light is to prevent the lenses from reflecting it, which is achieved by coating the lenses with multiple layers of antireflective metals. “An uncoated glass surface will reflect 10 percent or more of light, and if you have five or six surfaces, you lose 10 percent each time it goes through a lens,” explains Rob Fancher, a spokesman for Swarovski Optik North America, which cosponsors the Cornell team. The coatings also prevent internal reflections, which can mar contrast and image quality. Some companies skimp by coating only some lenses, but the superior binoculars will feature what is described as “full multicoating on all lens-to-air surfaces.”
The greater a binocular’s magnification, the more available light and light-capturing ability it requires to function optimally. Binoculars with a 10×42 designation will magnify an object by a factor of 10 through a 42-millimeter objective lens. However, all other factors being equal, an 8×42 will be more effective than a 10×42 in low light.
The most common magnifications are 8 and 10, although some binoculars can magnify by a factor of 20 or greater. While more magnification appears to bring objects closer to you, it also tends to exaggerate normal hand shakiness, making it look as though you are watching an earthquake when you peer through the scopes. A larger objective lens will increase the amount of light captured and the field of vision, but the trade-off is a bulkier and weightier binocular. Lens sizes typically range from 20mm for pocket binoculars to 56mm for full-size binoculars.
A high-end binocular will be fog-proofed by replacing the air inside the tubes with nitrogen. Most are also waterproof (as opposed to just water-resistant), which any birder, hunter, or hiker with streams to ford will appreciate. Many top binocs are shockproof as well, and top brands such as Swarovski, Leica, and Zeiss provide lifetime warranties that cover not only wear and tear, but also most accidents.
“Someone sent in a pair of binoculars that were chewed up in Africa,” says Jason Claybrook, a Zeiss spokesman, of a pair that had been savaged by hyenas. “All of the rubber was off, and it was covered with teeth marks.” Zeiss replaced the binoculars with a new pair. If it had been run over by a Land Rover, though, the customer would not have been so fortunate. “That’s just carelessness. We use our discretion.”