Prism Type | Glossary

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Most modern binoculars are made with an element called prism which is responsible for the rotation of the image upright as the viewer sees it. Prism in binoculars also determines their size, shape, optical features and plays an important part in providing image quality of binoculars. However, prism is the most neglected factor in the process of buying binoculars. There are many types of prisms present which normally determine the purpose of a certain binoculars – whether they are for hunting, marine, bird watching etc.

Prism Type

Source: Lovec

Porro Prism Binoculars

 

Binoculars that contains Porro prism (named after Italian physic Ignazio Porro) in their optical construction were predominantly the first type of binoculars on the market. In the last couple of decades, binoculars with Roof prisms (either Schmidt-Pechan or Abbe- Köning) became more popular, due to their compactness and water-tightness. This traditional arrangement of binoculars provided by Porro-prisms makes objective lenses further apart and thus offering a higher light transmission rate. Images are not only brighter and sharper but also have a better depth of field, offering realistic 3D images and wider field of view. Many Porro prism binoculars have also focusing mechanism separated for each eye, which can be very useful in low-light situations, when observing at dusk and at dawn. Even though Porro prism binoculars are becoming rare in today’s times, this traditional arrangement makes them more affordable due to less expensive manufacturing. But wider design makes them heavier and difficult to hold in hands and they are less watertight and also less rugged, providing a less secure grip. The other disadvantage of Porro prism binoculars is also the lack of adjustable eyepieces, which in most cases leads to problems when using the binoculars with glasses.

Features of Porro Prism Binoculars

  • (+) higher light transmission rate
  • (+) better depth of view perception
  • (+) wider field of view
  • (+) realistic 3D images
  • (+) lower price for high-end binoculars
  • (-) heavy and clumsy
  • (-) less watertight

Abbe/Koenig Roof Prism Binoculars

 

Binoculars with roof-like prisms in their optical construction provide compact design due to straight-line position of eyepieces and objective lenses. They are more expensive due to complex manufacturing and are providing many advantages for more demanding users. They are less sensitive to impacts and abrasions and are incredibly impervious for water and dust entering the construction. They are usually purged with nitrogen or argon gas, which also helps to eliminate internal glass fogging. Compared to Porro prism binoculars, they are more likely to withstand extreme weather conditions. Very good ergonomic design of this straight-line construction makes them less difficult to hold in hands and eases your portability immensely. But compared to Porro prism binoculars, this construction makes light transmission less permeable and thus providing darker and less sharp images.

Roof prism binoculars are divided in two main groups with the following types of prisms:

Roof prism binoculars according to the types of prisms

1. Schmidt – Pechan

  • (+) compact
  • (+) lightweight
  • (+) good ergonomics
  • (+) easy handling
  • (+) central focusing
  • (+) waterproof
  • (+) adjustable eyepieces
  • (-) lower light transmission rate compared to Abbe-König

2. Abbe – König

  • (+) compact
  • (+) better light transmission
  • (+) easy handling
  • (+) central focusing
  • (+) waterproof
  • (+) adjustable eyepieces
  • (-) expensive
  • (-) longer design

 

The main difference between both types of binoculars with Roof prism is that those with Schmidt – Pechan prisms tend to be smaller and less expensive, while those with Abbe – Köning prisms tend to have better light transmission rate and have a longer design.

 

Schmidt/Pechan Roof Prism Binoculars

 

Binoculars with roof-like prisms in their optical construction provide compact design due to straight-line position of eyepieces and objective lenses. They are more expensive due to complex manufacturing and are providing many advantages for more demanding users. They are less sensitive to impacts and abrasions and are incredibly impervious for water and dust entering the construction. They are usually purged with nitrogen or argon gas, which also helps to eliminate internal glass fogging. Compared to Porro prism binoculars, they are more likely to withstand extreme weather conditions. Very good ergonomic design of this straight-line construction makes them less difficult to hold in hands and eases your portability immensely. But compared to Porro prism binoculars, this construction makes light transmission less permeable and thus providing darker and less sharp images.

Roof prism binoculars are divided in two main groups with the following types of prisms:

Roof prism binoculars according to the types of prisms

1. Schmidt – Pechan

  • (+) compact
  • (+) lightweight
  • (+) good ergonomics
  • (+) easy handling
  • (+) central focusing
  • (+) waterproof
  • (+) adjustable eyepieces
  • (-) lower light transmission rate compared to Abbe-König

2. Abbe – König

  • (+) compact
  • (+) better light transmission
  • (+) easy handling
  • (+) central focusing
  • (+) waterproof
  • (+) adjustable eyepieces
  • (-) expensive
  • (-) longer design

The main difference between both types of binoculars with Roof prism is that those with Schmidt – Pechan prisms tend to be smaller and less expensive, while those with Abbe – Köning prisms tend to have better light transmission rate and have a longer design.

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