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....
I lift my binoculars and follow the family as they stalk through the marsh. Their movements are deliberate, regal, and severe, a march of impossibly tall, thin, chopsticklike black legs propping up snowy white feathers, so bright in the sun that it almost hurts to look at them. They are...