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Old Monday 13th November 2006, 15:55   #1
JTF
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Porro Prism vs Roof Prism

I wear eye glasses and do alot of birding. ID from distance is important, what is the difference between the two types of lenses. Pro's/Con's etc. Thanks for any help.
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Old Monday 13th November 2006, 16:43   #2
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Lots of differences, but greater FOV often gotten from porros. And for the low price end, porros are better optics.
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Old Tuesday 14th November 2006, 16:50   #3
richard866945
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Porro vesus roof prisms

The difference between roof and porro is in the prisms not the lenses. Roof prisms have an inherent problem with focusing all of the different wave lengths onto the same point unless they are phase correction coated so a 50 porro will be much better than a 50 roof model ( unless phase coated)especially as roof prisms cost more to make. Porro usually also tend to give a better 3D effect as the object lenses in a porro bino are wider spaced.
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Old Tuesday 14th November 2006, 17:18   #4
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Would anyone like to speculate as to which price point the two designs
become an even match,as regards to image quality.

There are many quality porro prisms that are priced around the 150 mark,
I wonder how much extra money you would need to spend to get a roof prism of equal image quality?

As for my own input,i've found very few budget roofs that come close to a well chosen 150 7/8x42 porro.The swarovski slc 8x30 is about the best
image i've found so far at the mid range level,obviously the more you spend
from this point the better the optics get.

In short,if I couldn't spend more than 500 on a roof,maybe i'd stick with a
cheaper swift porro or similar.

Matt
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Old Wednesday 15th November 2006, 13:42   #5
FrankD
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Quote:
Would anyone like to speculate as to which price point the two designs
become an even match,as regards to image quality.

There are many quality porro prisms that are priced around the 150 mark,
I wonder how much extra money you would need to spend to get a roof prism of equal image quality?
I do not think there is a price point where the two designs match. You pay considerably less to get a porro of any given image quality level in comparison to a roof. The highly regarded Nikon Superior E 8x32 is arguably the best central focus porro prism binocular made for mass production. To get its image quality level you have to pay well over $1000 in the roof prism design. On the other end of the scale something like the Nikon Action or Action EX provides comparable image quality to that of the Nikon Monarch ($200 price difference on average) with some noticeable trade-offs in one area or another. There really isn't a specific price point where you get comparable image quality with both roofs and porros at least not in my experience.

I do not know what that 150 currency value would translate into in US dollars but assuming a $200 US porro I would think you would have to pay at least twice the cost to find a roof comparable in image quality with some notable exceptions.

Last edited by FrankD : Wednesday 15th November 2006 at 13:46.
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Old Wednesday 15th November 2006, 15:38   #6
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Excellent as it is, the Nikon 8x32 SE is optically pretty ordinary except for an unusually sophistacated eyepiece. It might be thought of as a $300 binocular combined with a set of $400 eyepieces. It matches or exceeds the performance of the best roof prism binoculars because, with reasonable care in manufacture, there is not much wrong with a cemented doublet objective and a simple Porro prism. Combine those with a sophisticated eyepiece and the result is about as good as binoculars get. On the other hand, making a good roof prism binocular is essentially like making a silk purse from a sow's ear. The Schmidt-Pechan roof prism, in particular, is a design with so many disadvantages compared to Porro that it would never be chosen if optical quality is the only criterion. Even after expensive fabrication to much tighter tolerances, phase correction and mirror coating with dielectric coatings it still probably won't be quite as good as the prism cluster in a typical $150 Porro.

Last edited by henry link : Wednesday 15th November 2006 at 19:37.
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Old Wednesday 15th November 2006, 16:05   #7
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The major advantages of a well made roof glass are:
lighter and more compact
easily made waterproof
more shock resistant and
easily made to focus more closely.

Of the above only the last is an optical quality. Therefore, with the generally narrower fields of view, one is paying perhaps 50% more to obtain roughly equal optical performance in a better package.

Happy bird watching,
Arthur Pinewood
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Old Wednesday 15th November 2006, 18:13   #8
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Very well written post's, thanks for all the excellent input.
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