Stupid question time

[Allan Hobbs]

Why are the different types of binoculars called roof or porro?

[delia todd]

Why are the different types of binoculars called roof or porro?

And which is which? I never can get that into my head:gh:

D

[marcus]

Well, the roof binos have that name because their prisms are attached on their tops or 'roofs'. I don't know where that Porro name comes from.

[ceasar]

Let me try, Allan.

Prism's are named, as I understand it, after their inventors. The Porro Prism was invented by Paolo Ignazio Porro. These are used in the "Z" shaped, larger binoculars you often see. Roof Prisms are used in the "Straight Line" binoculars which are very popular. As I understand it the word "roof" is an English translation of the German word "dach." There are a number of design types of Roof Prisms used in todays binoculars. The most popular design is the Schmidt/Pechan roof prism, designed by two gentlemen: Schmidt and Pechan respectively. They are more complicated and costly to make than Porro Prisms and require a specific coating known generally as "phase coating" in order to bring the image to ideal sharpness. Porro prisms don't require this coating.

I will now bow out and go into hiding and let the experts take over. Meanwhile you can visit this site where you will find much useful information.http://www.eagleoptics.com/index.asp?dept=1&type=27&subtype=92&purch=0 On page two of this particular article you will find designs of both type prisms.
Cordially,
Bob

[elkcub]

They are different basic designs for the image inverter prisms used in binoculars. Porro is named after the inventor as explained here:

http://www.eagleoptics.com/index.asp?pid=2392

Good question.
Elk

[Tero]

As to why two are still offered:
porros are good optics, some people like them, I only like reverse porros

roof prisms are lighter, waterproof, and the objective lenses are about the same length apart as your eyes, a natural way of looking

for astronomy, porros are still popular, and mounted 20x or more are not unusual

[ThoLa]

As to why two are still offered:
porros are good optics, some people like them, I only like reverse porros

roof prisms are lighter, waterproof, and the objective lenses are about the same length apart as your eyes, a natural way of looking

for astronomy, porros are still popular, and mounted 20x or more are not unusual


Porro-models can be waterproofed, too. And the image is just as natural or unnatural as in a roof-prism model.
Roof prim model are more popular because they more fashionable. They are not technically superior.

T

[etc]

Apparently when you see an image through a magnifying glass, it's upside down. These prisms turn the image upside down so you see it as it appears in real life.

Leica and Swarovski use Schmidt-Pechan prism, Zeiss uses Abbe-Koenig prism.

http://en.wikipedia.org/wiki/Roof_prism

http://en.wikipedia.org/wiki/Schmidt-Pechan_prism

http://en.wikipedia.org/wiki/Abbe-Koenig_prism

[etc]

My first bino was an old copy of Zeiss porro. I think it was 7x30.

I also got some Leica roofs. Not sure about the visual difference, but I think they advantage is they are more compact and more waterproof.

[ThoLa]

Zeiss uses Abbe-Koenig prism.


In some models, yes, in others, no.

[ThoLa]

more compact and more waterproof.

what's more waterproof?

Sounds like: this corpse is more dead than the other. :-C

[iveljay]

Depends on your definition of waterproof - most will leak if you subject them to water pressures significantly greater than their design point.

In fact its a bit like waterproof clothing - as most of us have found out the hard way.

I have only once left bins out in torrential rain for a long time once by accident and fortunately they did live up to the claim. They were roofs but I have been out with porros in atrocious weather with no obvious ill effect though I wouldn't risk the EIIs !

For my particular 'paws' and eyes a porro is usually easier to hold steady and gives a more natural image but for travelling a roof is lighter and takes up less space. Really its horses for courses.

J

[Allan Hobbs]

Thanks everyone for all the info. I am constantly amazed by the breadth of knowledge shown by memebers. Hopefully some will rub off onto me at some point ;)