RECREATIONAL BIRDING RESOURCES
Binoculars are invaluable for viewing distant birds. Often observers can spot birds flying between trees or perched high up in a tree but cannot see the bird’s field markings. Binoculars help in bird identification and in the enjoyment of watching bird behaviors. To use binoculars the observer follows the moving bird to its new perch and then while keeping eyes on the bird, brings the binoculars up to the eyes. If you buy your binoculars from a nature store that specializes in optics for birders, you will be assisted in how to select the right pair for your eyes and in setting it up for ease in focusing once you have spotted that bird.
Here are a few suggestions for selecting the right pair of binoculars. Read the book, Pete Dunne on Bird Watching, for further details.
Size and shape — Choose binoculars (bins) that once adjusted produce a single image (i.e., ocular lens fits your interpupillary distance). Choose binoculars that are easy to grasp and hold firmly while maneuvering the focus wheel with your index finger.
Weight — Lighter weight binoculars are easier to hold while locating and studying a bird’s features.
Design — Choose between Porro prism and roof prism. Porro prism binoculars are usually wide-bodied and the front lens (objective) and back lens (ocular) are not lined up along a linear axis. They use fewer reflecting surfaces and thereby reduce light loss and image distortion. Roof prism binoculars are easier to hold and use because of its sleek back-to-front linear design and better overall image quality in higher magnifications. Its disadvantages are increased loss of light and introduction of light-wave shift that reduces image contrast. Differences, however, are reduced in higher quality and more expensive binoculars.
Focus System — Choose binoculars with a center-focus wheel for quick and easy adjustments between distant and nearby birds. Avoid lever or bar focus systems as well as permanent-focus or no-focus systems.
Magnification — Most birders choose between 7x to 10x power for magnification. Higher magnifications enables viewing of more distant objects but reduces field of view and depth of field. Higher magnifications may lose light or cause darker images.
Exit Pupil Size — is the diameter number calculated by dividing the size of the objective lens by the power of the binocular. For example, a 7x 42 binocular has a 6 millimeter exit pupil. Objective lens sizes used by birders range from 30 to 50. The larger the objective lens number the more light enters. Choose 5-6 mm and never less than 3.75 millimeters.
Choose BAK-4 glass or denser; HD (high-density) glass
Choose fully multicoated optics. Roof prism binoculars need phase-corrected coatings.
Choose 10-15 feet for close focusing
Field of View
Choose no less than 330 feet at 1,000 yards.
18 millimeters is preferred by many. Eyeglass wearers need at minimum 15 millimeters
For bird watching in fog, rain, snow, or sleet and offshore or in the tropics, be sure the binoculars are waterproof and rugged