While selecting binoculars, you can choose two different prism styles you can choose.
When the lens enters the lens, it is a zig-zag with a distance to reach your eyes. Until the roof prism was turned on the binoculars, these prisms were standard.
The most notable advantage of a bird prism is that they are cheaper than the roof prism, which means you can get high-quality binoculars for the same price.
The disadvantage is that the panoramic binoculars are more complex, holes, and almost strange to carry! I think they are very old and look out of style. I still have a hard time finding Porro Style binoculars for sale.
The light of the roof prism allows your eyes to go directly through the barrel. Although the roof prism is smaller than the compact, streamlined and porro prism, internally it is even more complex.
Highly Recommended: Most hunter-gatherers and birds will be watching a telescope and a roof prism design. They are pretty easy to carry around and use. They are very good in your hands and the weight is low and the distance of Porro prism.
***For specific binocular recommendations for bird wathcing, Try this post. Click here