If you've ever looked through binoculars, a telescope, or a magnifying glass, you'll know that some lenses magnify (or reduce) the apparent size of an object much more than others. There's a simple measurement that tells you how powerful a lens is and it's known as the focal length....
Instantly, and without binoculars, Montemayor names it: “That’s a roseate spoonbill.” He keeps up this patter more or less nonstop for the almost five hours of our tour, identifying forty species in all and writing each name with a pen in a little black notebook. This is just one ...