There are two primary types of prisms used in all binoculars. The most common is the Porro prism. This type uses offset prisms to increase the image your binoculars can see in a compact design. Inside the binocular the image is inverted and then re-oriented to be right side up. Meanwhile, the path that light travels down inside the binocular is Straight Binoculars . The roof prism marine binocular is durable, heavy binocular that delivers a clear image, but for similar quality viewing it is more expensive than the Porro prism style.

Now let's get to the features that make binoculars stand out from the pack. First, waterproofing is an absolute essential; field binoculars that are not waterproof will probably be ruined at their first appearance on board your boat. Second, lens coatings that provide protection against fog and moisture are worth their weight in gold. Look for marine binoculars that are o-ring sealed to keep out condensation.
 

Key words:  Straight Binoculars ， Binoculars
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