Binoculars and Scopes
Check The Coating
To reduce reflection on glass surfaces - outside and inside the instrument - lens are coated with non-reflective compounds. Better binoculars and telescopic sights should be fully coated, meaning the material has been put on all surfaces.
The simple statement, "coated optics," likely means some of the surfaces aren't coated, which could diminish the crispness of the image. Make sure the maker specifies "fully-coated."
The coating should show on the front lens. Look for a blue, purple, or yellow haze. Though the yellow coating is harder to distinguish, it is just as effective as the blue or purple coatings.
Also, note whether some of the coating already has rubbed off or worn away. Coatings are delicate and do show wear with time, but there's no sense in buying a binocular or scope with wear already built-in.
Grade The Prism
Binoculars and spotting scopes with offset barrels contain prisms as part of their optical systems, and it's possible to tell whether an instrument has standard prisms or those of a better grade.
Hold the instrument at arm's length and look through the eyepiece. If the eyepiece seems to have a shadow-square appearance, then the prism is standard.
If, however, the exit pupil looks perfectly round, that indicates a much better grade.
When viewed through a scope or binoculars at 50 yards, letters on a street sign should not appear fuzzy. Straight lines - the top rail of a fence, the corner of a building - should not show as bent or distorted at the edges.
For more ways to judge quality optics, go to Page 2.