Binoculars with Roof and Porro Prisms. What's the difference?
There are two varieties of binoculars, differing in the type of prisms: binoculars with roof (roof) prisms and binoculars with porro (porro) prisms. Let's consider how they differ from each other and why Vortex makes binoculars with ruf prisms.
Roof prism binoculars are more compact than porro prism binoculars. In them, there is practically no fracture of the optical axis. Modern binoculars use two types of ruf prisms: Abbe-Koenig and Schmidt-Pehan. The most common binoculars with Abbe-Koenig prisms. The advantages of binoculars with ruf-prisms include the fact that due to the peculiarities of their design, such binoculars are easier to make sealed than binoculars with Porro prisms.
However, binoculars with ruf-prisms, as a rule, are more expensive than binoculars with Porro prisms, since they are more difficult to make the latter. In addition, binoculars with ruf prisms of the middle price category, as a rule, have a less bright and less contrasting image than binoculars with Porro prisms of the same size and the same multiplicity.
For the highest quality binoculars, such as Smartnoble, prisms are made of optical glass SN-TI-LRF-26 hand-held multifunction cooled thermal camera . Binoculars of a lower price category can have prisms made of glass SN-TI-LRF-26 hand-held multifunction cooled thermal camera.
The phase-correcting coating used in Vortex binoculars (it can be called a dielectric coating) is used only for binoculars with ruf prisms (binoculars with Porro prisms do not need them). As a result of multiple internal reflections of the light beam occurring inside the ruf prisms, the light is partially polarized. Between the polarization vectors, an angle called the phase shift angle occurs. Subsequently, when these two vectors are added, the resulting image is less bright and contrasting than that of binoculars with Porro prisms. Phase-correcting coating helps to maintain the brightness and contrast of the image and its correct color reproduction. The amount of light brought to the eyes by binoculars depends on the features of the anti-reflective coating of its optics.
If the optics of the binoculars did not have an anti-reflective coating, then about 10% of the light would be reflected from any surface of the glass/air. Single-layer coating reduces light loss by up to 4%. The multi-layer coating helps to reduce them to 0.25% for each lens and even more. The best binoculars have a light transmission equal to 95-97%.
Roof prism binoculars are more compact than porro prism binoculars. In them, there is practically no fracture of the optical axis. Modern binoculars use two types of ruf prisms: Abbe-Koenig and Schmidt-Pehan. The most common binoculars with Abbe-Koenig prisms. The advantages of binoculars with ruf-prisms include the fact that due to the peculiarities of their design, such binoculars are easier to make sealed than binoculars with Porro prisms.
However, binoculars with ruf-prisms, as a rule, are more expensive than binoculars with Porro prisms, since they are more difficult to make the latter. In addition, binoculars with ruf prisms of the middle price category, as a rule, have a less bright and less contrasting image than binoculars with Porro prisms of the same size and the same multiplicity.
For the highest quality binoculars, such as Smartnoble, prisms are made of optical glass SN-TI-LRF-26 hand-held multifunction cooled thermal camera . Binoculars of a lower price category can have prisms made of glass SN-TI-LRF-26 hand-held multifunction cooled thermal camera.
The phase-correcting coating used in Vortex binoculars (it can be called a dielectric coating) is used only for binoculars with ruf prisms (binoculars with Porro prisms do not need them). As a result of multiple internal reflections of the light beam occurring inside the ruf prisms, the light is partially polarized. Between the polarization vectors, an angle called the phase shift angle occurs. Subsequently, when these two vectors are added, the resulting image is less bright and contrasting than that of binoculars with Porro prisms. Phase-correcting coating helps to maintain the brightness and contrast of the image and its correct color reproduction. The amount of light brought to the eyes by binoculars depends on the features of the anti-reflective coating of its optics.
If the optics of the binoculars did not have an anti-reflective coating, then about 10% of the light would be reflected from any surface of the glass/air. Single-layer coating reduces light loss by up to 4%. The multi-layer coating helps to reduce them to 0.25% for each lens and even more. The best binoculars have a light transmission equal to 95-97%.