18 replies to this topic

[Jeronimo Cruz]

Hi all,

Here is a summation of what I've gathered regarding the differences between porro and roof prism binoculars. Can you help me expand it?

Porro prism binocular advantages:
-brighter image vs. roof prism
-cheaper to manufacture to a high standard
-more fully illuminated exit pupils vs. roof prism
-wider TFOV vs. roof prism (shorter light path vs. roof prism)
-better depth of field vs. roof prism (improved steroscopic view)
-accomidates bigger hands

Porro prism binocular disadvantages:
-collimation can be more easily misaligned
-external focusers w/bridge can be more difficult to truely waterproof
-longer close focus vs. roof prism
-larger apertures can be too big and bulky for smaller hands


Roof prism binocular advantages:
-more compact vs. porro prism
-lighter vs. porro prism
-fixed prism housing that holds collimation better than porro prism
-better close focusing ability vs. porro prism
-smoother focuser operation which is more adaptable to observing moving subjects
-better waterproofing vs. porro prism due to internal focuser

Roof prism binoculars disadvantages:
-much more expensive per aperture due to smaller prisms, phase coatings, and dielectric coatings
-dimmer image vs porro prism
-worse depth of field vs porro prism
-maximum aperture limited to 63mm due to interpupilary restrictions



I appreciate your responses.

Thanks!

[daniel_h]

i agree with most suggestions - from my own experience

[Swedpat]

I think you have mentioned the main differences between roof and porrobinoculars. But are roofglasses really dimmer than porros? I doubt about that, and I don't think the prisms have to be less illuminated.

Of course, now we are just waiting for EdZ or BillC to get the definitive answer about this issue...

Regards, Patric

[Erik D]

Jeronimo,

Your summary of roof vs porro design is for the most part correct. However, binocular selection is very personal, difficult to make based on generalizations. I have a pair of Oberwerk 12X60 porros with 5.7 deg FOV, price is $109. Have not used them much for the past 4 years.....since I purchased a pair of Leupold Olympic 12X50 roofs for ~$350.

The Leupold has narrower 4.8 deg FOV but the color fidelity, resolution and focuser is superior to the Oberwerk. For astronomy use the Leupold see dimmer stars by a slight margin even though the 60 mm Oberwerk is suppose to gather ~30% more light. (I have learned the lower cost 60 mm Oberwerk has effective aperture closer to 50 mm since) I carry the Leupod with me every chance I get. It's no heavier than my Clestron Regal 10X42 . (Another excellent Roof prism)

The Leupolds 12X50 roof cost me more than 3X the price of the Oberwerk 12X60 porro but it's a better VALUE for me. I have purchased at least 1/2 dozen more binos since getting the Leupold. It's difficult to summarize the Quality of viewing experience with numbers or general rules of one design vs. the other.

I discussed my preference in more detail in this thread: http://www.cloudynig...sb/5/o/all/vc/1

Based on input from CN members I understand the $150 Oberwerk 12X50 roof is worthy of consideration, even though it does not have phase coating. I do not have first hand experience.

ERik D

[KennyJ]

I find that even high priced roof prism binoculars tend to show more spikes from bright light sources than Porros do .

Inexpensive models of either design can be just as bad as each other in most respects .

Both are very old , proven successful designs that for providing correct - orientation , two - eyed images , have yet to be bettered by anything different .

Kenny

[EdZ]

Here's a few comments on some of these suggestions:

Porro prism binocular advantages:
-brighter image vs. roof prism NO
the binocular with the larger exit pupil is going to show the brighter image.

-more fully illuminated exit pupils vs. roof prism YES
almost all porros have better illumination than almost all roofs

-wider TFOV vs. roof prism (shorter light path vs. roof prism) NO
I've tested numerous roofs of same size that are wider than porros
shorter light path really has nothing to do with it, it's dependant on field stop diameter


Porro prism binocular disadvantages:
-larger apertures can be too big and bulky for smaller hands
BUT in any side-by-side, you would be comparing like size aperture, so no disadvantage here


Roof prism binocular advantages:
-lighter vs. porro prism
sometimes, but not always
Fujinon BFL 8x42, Swift Ultralite 8x42, Orion Vista 8x42 are lighter than any roof I've ever used.

-smoother focuser operation which is more adaptable to observing moving subjects
a function of price and quality, I've used porros with better focusers than roofs


Roof prism binoculars disadvantages:
-much more expensive per aperture due to smaller prisms, phase coatings, and dielectric coatings
due to more expensive to make precise angles in prisms.

-dimmer image vs porro prism
the binocular with the larger exit pupil is going to show the brighter image.

-maximum aperture limited to 63mm due to interpupilary restrictions
well, it's a limitation, but not a disadvantage. refer to your comment above where you referred to a Porro prism binocular disadvantages: -larger apertures can be too big and bulky for smaller hands
Same holds true for either one.

FWIW, I would say that a lot of these comments are too generalized to be consistently true. A number of them are definitely model specific, and a number of them are price/quality specific, but would not necessarily hold true across a porro/roof debate.

edz

[Luigi]

>>>maximum aperture limited to 63mm due to interpupilary restrictions<<<

The EP and objectives do not have to be collinear in roofs. Look at many of the Swarovski bins and Zeiss 10x56 Victorys as examples. Examples lower down the food chain include the Barska 9x63 roofs and the Vortex 10x50 Razors.

[edwincjones]

but the bottom line just comes out to personal preference

edj

[Man in a Tub]

I follow threads about porro and roof prisms with interest. For about a year, I retired my Brunton Eterna 15x51 roof prism from stargazing. It ended up in its box in a closet. That was really a mistake. So, I've been using it again since late April. I'm no good at testing it precisely against my other binoculars. However, I enjoy the Brunton Eterna 15x51 views over a range of observational situations: doubles, star colors, the "brighter" star clusters and selected starfields.

P.S. To my eyes, the Brunton delivers the sharpest view of Jupiter and the Galilean moons. It outperforms my Nikon 12x50 Action EX and Oberwerk 15x60.

[pcad]

If the definition of a roof prism binocular includes any combination of prisms that includes a roof prism element, then roof prism prism binoculars can have objectives larger than 63 mm. One way of doing this would be to include a rhomboid prism to shift the optical axis and allow the eyepieces to be closer together. One example is the Newcon IS binoculars that use S-P prisms then rotatable Rhomboid prisms to adjust IPD. There are other examples also.

[DJB]

Hi Edz,

I do believe that you have put into words about the comparisons that I never did. I always kept them in "my head" as impressions. However, thank you for your understanding of the two.

I would advise anyone who is interested in this material to keep this post in a safe place for a reference.

Best regards,
Dave.

[Jeronimo Cruz]

Hi EdZ,

From my own experience, porro prism binoculars are brighter (generally) than roof prism binoculars. For example, I have Pentax 10x50 SP's and Pentax WPII 10x50's. The exit pupils are the same size. I use my binos on a nightly basis and the WPII's are clearly bighter than the SP's. The SP's have a sharper field and much better contrast, but the WPII's are unmistakeably brighter. And the Pentax states that they used a "no holding back" mentality when designing the SP line. Only a couple of years ago the SP line was pentax's top of the line before the DCF ED line was introduced. My SP's have outstanding coatings bested only by my Fujinon's. I also have other binoculars of both types that reflect the same thing.

Online, the general concensus is that roof prism binoculars, generally speaking, can be made made as bright (at great expense) as porro prism binoculars but never surpass them. By design, roof prisms have a reflective surace that slightly decreases light transmission (even w/diaelectric coatings). The porro design does not use a reflective surface at all and is therefore inherently brighter than a roof prism of the same optical quality. Am I mistaken?

Does your experience using roof prism and porro prism binoculars of the same aperture and with equal exit pupils lead you to a different conclusion?

Thanks!

[Erik D]

From my own experience, porro prism binoculars are brighter (generally) than roof prism binoculars. I have Pentax 10x50 SP's and Pentax WPII 10x50's. The exit pupils are the same size. I use my binos on a nightly basis and the WPII's are clearly bighter than the SP's. The SP's have a sharper field and much better contrast, but the WPII's are unmistakeably brighter.

...........
Does your experience using roof prism and porro prism binoculars of the same aperture and with equal exit pupils lead you to a different conclusion?

Thanks!

Jeronimo,

When you say "The exit pupils are the same size" Is that measured or calculated?

Very few of us go thru the same meticulous process of measuring exit pupil size, verifying magnification, % illumination as does Prof Ed.

I am familiar with the Pentax DCF SP, HR II and ED line. I too would expect the SP to be at least the equal of the less expensive WP 10X50. But I wonder if there is some other factor at work besides exit pupil size.

Soon after I purchased my Leupold Windriver Olympic 12X50s roofs I picked up the 12X60 Oberwerk porro prism to compare the view. I was surprised that I could not pick out dimmer stars in the 60 mm Oberwerks despite their 44% more light collecting area. I thought I was imagining things. After several more sessions I picked out a DSO at the threshold of visibility in the 12X60 porros with averted vision. Put down the 60mm Oberwerk and viewed the same object with the Leupold roofs. I could see it with direct vision. Later I learned the 60 mm Oberwerk has an effective aperture closer to 50 mm.

For ME the porro vs roof design debate are of secondary importance. I understand the Nikon action EX 12X50 porro is a really fine binocular. Very close to the reference standard Superior E 12X50. But I have no intention of replacing the Leupold 12X50 roofs with the . The 25.7 oz Leupols roofs are much more compact than the 37 oz Nikon EX. I willl take my 12X50 Leupold roofs on international trips and keep them in my pack all day. I would not pack full sized 50 mm porro on the same. Close to home I can always go to my mounted 20X80 or bigger binoculars if I want to see deeper. I enjoy giant binocular astronomy very much. Porro prisms are the only game in town if I wanted binos bigger than 60 mm anyway.

I have never measured exit pupil size or tried to verify exact magnification of any of my binoculars. I was a mechanical engineer by training. I know theory and practice are two different things. Hand 5 people a micrometer and a known diameter bar stock. Ask them to take 3 reading and they are likely come up with varying results. Accurate measurement of exit pupil presents different set of challenges. I am more skilled at other type of measurements so I leave these two factors to those who have the time, patience and skill. For me, resolution, color fidelity, image sharpness and the over all quality of view are more important. Make sense?

Some day my observing skills may improve to the point where I can tell if I am looking at stars 0.2 mag dimmer with one design or the other. I can't now and that's fine too.

ERik D

PS. I should add that over 66 % of my binocular use are in the day time so my priorities are different.

[Jeronimo Cruz]

Hi Eric D,

You asked if the 5mm exit pupil value was calculated or measured. Good question. The figure was calculated. It spurred me to measure the exit pupils with a ruler and they are indeed 5mm for both the Pentax DCF SP and WPII 10x50's. This confirms the value stated in Pentax literature.

[pcad]

Jeronimo,

The Schmidt-Pechan design does have one mirrored surface on the Pechan prism.

The Abbe-Konig design has no mirrored surfaces.

Both need phase correction coatings on the roof surface/surfaces to equal the Porro design.

[Erik D]

P.S. To my eyes, the Brunton delivers the sharpest view of Jupiter and the Galilean moons. It outperforms my Nikon 12x50 Action EX and Oberwerk 15x60.

Interesting. I don't have the Nikon Action EX but I know it's held in high regard. I have not used my Brunton 15X51 for some time. I am going to set up the Brunton's next to my Leupold 12X50 roofs next clear light and have a look at Juipter. I Never liked the view of Jupiter and Saturn in low cost 60-80 mm Chinese binoculars.

ERik D

[EdZ]

Hi Eric D,

You asked if the 5mm exit pupil value was calculated or measured. Good question. The figure was calculated. It spurred me to measure the exit pupils with a ruler and they are indeed 5mm for both the Pentax DCF SP and WPII 10x50's. This confirms the value stated in Pentax literature.

I would say measuring exit pupils requires either a caliper with division to tenths of a mm or a loupe (at least 6x or 8x) with a calibrated scale that can be estimated to half mm.

edz

[EdZ]

Hi EdZ,

From my own experience, porro prism binoculars are brighter (generally) than roof prism binoculars. For example, I have Pentax 10x50 SP's and Pentax WPII 10x50's. The exit pupils are the same size. I use my binos on a nightly basis and the WPII's are clearly bighter than the SP's. The SP's have a sharper field and much better contrast, but the WPII's are unmistakeably brighter.

Online, the general concensus is that roof prism binoculars, generally speaking, can be made made as bright (at great expense) as porro prism binoculars but never surpass them. By design, roof prisms have a reflective surace that slightly decreases light transmission (even w/diaelectric coatings). The porro design does not use a reflective surface at all and is therefore inherently brighter than a roof prism of the same optical quality. Am I mistaken?

Does your experience using roof prism and porro prism binoculars of the same aperture and with equal exit pupils lead you to a different conclusion?

Thanks!

The most important point I want to drive home, as I said in my post above, is that these issues are not "type" specific, they are "model" specific. For instance you gave an example to support your case. Here's examples to counter your case.

Porros
Swift Ultralite 8x42, ep=5.1mm, Afov=52
Pentax PCF WP 8x40, ep=5.2mm, Afov=47
the Swift- less than 5% of the center of the lens provides 100% illumination, lux reading with light meter is 630
the Pentax- 28% of the center of the lens provides 100% illumination, lux reading with light meter is 637

Roofs
Bushnell Legend 8x42 Roof, ep=5.1mm, Afov =54
Garrett DCF 8x42 ApoRoof, ep=5.2mm, Afov=54
the Bushnell - 15% of the center of the lens provides 100% illumination, lux reading with light meter is 627
the Garrett- 35% of the center of the lens provides 100% illumination, lux reading with light meter is 660

Each of these roofs is brighter than the porro to which it is compared.

Now, If I chose to, I could cite examples of each that would support your case, but that's my point, this is not a consistent trend across the porro/roof debate, so you can point to examples to support whatever side of the debate you select. Sure, I have porros that are same size and are brighter than roofs, but I also have/had roofs that are same size and are brighter than some porros.

For instance, I could have selected the Nikon SE 10x42 as my porro, but it is the only 10x42 porro I've ever seen. It just so happens, it's one of the best porros on the market. It handily beat out these five roofs.
Leica Trinovid 10x42 rp
Nikon Monarch ATB10x42 rp
Pentax DCFHRII 10x42 rp
Zen Ray Summit 10x42 rp
Celestron Regal 10x42 rp


On another note, FWIW, I've measured seven different Pentax binoculars, including one roof. Only two of them equal the specified exit pupil. Six of them have slightly reduced aperture. Five of them were measured to vary somewhat from the specified magnification.

edz

[Jeronimo Cruz]

Hi EdZ,

Thanks for your input! I appreciate your insight.

It appears as though roof prism binoculars have finally caught up to, and in some ways, surpassed porro prism binoculars. The choice boils down to the amount of money one would like to spend on binoculars and ergonomic/aesthetic preference. Neither type is best suited to every application. One should choose the type that best fits one's particular needs and budget.

I suppose that a roof bino's brightness is more a function of expense and craftmanship when all other things are equal.

It is important to know the strengths and weaknesses of both designs to best select the most appropriate binoculars for one's needs.

I realize I represent only one point of data, but it has been my experience that porro binos are brighter (generally speaking)than their roof counterparts of equal aperture and magnification.

:penny:

Again, thanks for your response EdZ.

Regards.