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Porro vs. roof prisms?
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Optics GrassHopper
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    Posted: March/27/2008 at 15:46
I'm a binocs newbie and have no idea what the difference between the two is.  Can anyone explain it to me in actual terms as well as any differences in performance. 
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Porro prisms have the familiar dogleg shape to the housings, where the objective lenses will be offset from the eyepiece lenses.  Roof prism binoculars have in-line housings, so they are generally more compact than porro prisms with the same objective lens diameter and magnification.  This compactness comes at a significant cost.  Comparing binoculars of equivalent optical quality, the roof prism will almost always be more expensive than the porro prism.  This is due to the more complex prism arrangement and reflective prism coatings (metallic coatings like aluminum or silver, or multilayer dielectric coatings) and phase correction required.  In a roof prism binocular the 2 prisms in each barrel are stacked on top of one another instead of offset so the light is reflected in more abrupt angles through the prisms.  A good roof prism binocular is just more costly to produce.
 
The very best roof prisms can equal, but usually not exceed the optical quality of the very best porro prisms, but again, at a substantially higher price tag.
Ted


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Originally posted by RifleDude RifleDude wrote:

Porro prisms have the familiar dogleg shape to the housings, where the objective lenses will be offset from the eyepiece lenses.  Roof prism binoculars have in-line housings, so they are generally more compact than porro prisms with the same objective lens diameter and magnification.  This compactness comes at a significant cost.  Comparing binoculars of equivalent optical quality, the roof prism will almost always be more expensive than the porro prism.  This is due to the more complex prism arrangement and reflective prism coatings (metallic coatings like aluminum or silver, or multilayer dielectric coatings) and phase correction required.  In a roof prism binocular the 2 prisms in each barrel are stacked on top of one another instead of offset so the light is reflected in more abrupt angles through the prisms.  A good roof prism binocular is just more costly to produce.


Absolute truth.
 
Originally posted by RifleDude RifleDude wrote:

The very best roof prisms can equal, but usually not exceed the optical quality of the very best porro prisms, but again, at a substantially higher price tag.

This certainly has been true for a long time.
It probably is still true right at this moment.
But, I doubt it will remain true for very much longer.

This isn't because there is anything inherently wrong with the basic premise but, simply because almost no one is making higher end porros any more.  Zeiss isn't.  Leica I don't think ever did.  Swarovski's Habicht is almost impossible to find. Nikon just recently has discontinued their legendary Superior E line.  Bausch & Lomb had both Elite and Discoverer porros which are both gone.

Porros have become pretty strongly entrenched in the field of low-cost, budget-class optics, which is a shame as they still could easily outperform the very best roofs if even half the attention was given to their design that is lavished on the roof prism design. However, no matter how good they are, high-end porros simply don't sell and so they are beginning to languish behind.
What if the hokey pokey really is what it's all about?
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Zeiss makes porros, but the importer in US are not importing it as they don't sell there.
But the 7x50B is still made and one of the absolutely best binoculars in it's class.
You can find them cheap on Ebay, usally sells for around 450-600 dollars.
 
Leica have made porros but it's long time ago.
 
Swarovski porros are better avoided.
I have a couple of 7x42 and they are miles behind the Zeiss.
 
I cannot really agree that roofs are more compact than porros.
They are more slim, but not more compact as a good porro like Zeiss is about 2/3 of the length of a equalivent roof.
 
Regards Technika


Edited by www.technika.nu - March/28/2008 at 02:20
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Originally posted by RifleDude RifleDude wrote:

Porro prisms have the familiar dogleg shape to the housings, where the objective lenses will be offset from the eyepiece lenses.  Roof prism binoculars have in-line housings, so they are generally more compact than porro prisms with the same objective lens diameter and magnification.  This compactness comes at a significant cost.  Comparing binoculars of equivalent optical quality, the roof prism will almost always be more expensive than the porro prism.  This is due to the more complex prism arrangement and reflective prism coatings (metallic coatings like aluminum or silver, or multilayer dielectric coatings) and phase correction required.  In a roof prism binocular the 2 prisms in each barrel are stacked on top of one another instead of offset so the light is reflected in more abrupt angles through the prisms.  A good roof prism binocular is just more costly to produce.
 
The very best roof prisms can equal, but usually not exceed the optical quality of the very best porro prisms, but again, at a substantially higher price tag.


Generally, a vey accurate statement.  One minor correction though: there are a couple of different types of roof prism arrangements.  The most common one, Shmidt-Pechan does require a reflective coating.  A somewhat rare one (used by Zeiss, bit not many others) is Abbe-Koenig which does not require that reflective layer, but at a cost of a longer binocular.

ILya
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Originally posted by koshkin koshkin wrote:

Originally posted by RifleDude RifleDude wrote:

Porro prisms have the familiar dogleg shape to the housings, where the objective lenses will be offset from the eyepiece lenses.  Roof prism binoculars have in-line housings, so they are generally more compact than porro prisms with the same objective lens diameter and magnification.  This compactness comes at a significant cost.  Comparing binoculars of equivalent optical quality, the roof prism will almost always be more expensive than the porro prism.  This is due to the more complex prism arrangement and reflective prism coatings (metallic coatings like aluminum or silver, or multilayer dielectric coatings) and phase correction required.  In a roof prism binocular the 2 prisms in each barrel are stacked on top of one another instead of offset so the light is reflected in more abrupt angles through the prisms.  A good roof prism binocular is just more costly to produce.
 
The very best roof prisms can equal, but usually not exceed the optical quality of the very best porro prisms, but again, at a substantially higher price tag.


Generally, a vey accurate statement.  One minor correction though: there are a couple of different types of roof prism arrangements.  The most common one, Shmidt-Pechan does require a reflective coating.  A somewhat rare one (used by Zeiss, bit not many others) is Abbe-Koenig which does not require that reflective layer, but at a cost of a longer binocular.

ILya
 
Correct on the AK prisms not requiring reflective coatings.  In the interest of brevity, I didn't include it as an exception in my response, but I'm glad you reminded me of this topic, because I've wondered what the optical advantage the AK prism still offers now that there have been so many advancements in dielectric coatings & Phase coatings.  Is there anyone else besides Zeiss in their Victory FL (42mm and larger objective models) and Conquest ABK that is currently using them?
 
Lucznik, you're dead on.  Porro prism binoculars are currently out of favor with serious optics enthusiasts and the manufacturers are taking notice and responding to what sells.  As roof prism binoculars get better and better, manufacturers are dropping their premium quality porro prism designs from their lineups and they're slowly being relegated to the "bargain" priced, low end models.  So although theoretically porro prism binoculars can provide optical advantages over the roof prism at lower cost and complexity, practically speaking, most of the top end binoculars currently being manufactured are roof prism designs.
 
Technika, roof prism binoculars may not always be more compact, and are frequently longer than porro prisms, but they have the potential to be more compact in the shorter focal length, mid-size objective models.  For instance, some of the premium 32mm objective roofs such as the Zeiss FL 32, Leica Ultravid 32 are more compact than any equivalent porro prism binocular of equal magnification, FOV, and opjective diameter.  With the same objective lens diameter, a roof prism binocular will always be at least narrower, if not shorter than a porro prism bino. 
Ted


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Ted, the only other roof binoculars that I can think of off the top of my head that have AK prisms are Optolyth.  I was impressed with a 7x42 Via Nova.

ILya
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Originally posted by grouper sandwich grouper sandwich wrote:

I'm a binocs newbie and have no idea what the difference between the two is.  Can anyone explain it to me in actual terms as well as any differences in performance. 


Here is a good website for newbies:Binoculars



Edited by Bird Watcher - March/31/2008 at 21:23
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