And you can accurately tell how far away that Crow is. In case he decides to swoop you.
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A comparison of prism types, and why the Schmidt Pechan seems to have won the premium binoculars (2 Viewers)
- Thread starter kimmik
- Start date
The Bresser 7x32 13 degree binocular uses mirror prisms.
It is awful.
Also in 8x42 and 10x50, I think.
My Yukon 30x50 uses only mirrors. The resolution is great and star images very good.
The problem is that with all Yukon products the coatings are poor.
So the transmission of the 30x50 is poor.
It splits 6.5 arcsecond double stars without a tripod.
My c.1955 16x56 Hensoldt is incredibly well built and very lightweight with a wide AFOV.
Regards,
B.
It is awful.
Also in 8x42 and 10x50, I think.
My Yukon 30x50 uses only mirrors. The resolution is great and star images very good.
The problem is that with all Yukon products the coatings are poor.
So the transmission of the 30x50 is poor.
It splits 6.5 arcsecond double stars without a tripod.
My c.1955 16x56 Hensoldt is incredibly well built and very lightweight with a wide AFOV.
Regards,
B.
henry link
Well-known member
I think this change in personel is the key to understanding why Zeiss binocular designs changed so radically between the 42mm FL/HTs and the 42mm SFs. Both Gerold Dobler and Konrad Seil had histories at Swarovski. When they joined Zeiss the first model they designed more closely resembled the original Swarovski EL from 1999 than it did any previous Zeiss binocular.
Vespobuteo
Well-known member
4 years is indeed a short product cycle for high-end binoculars.
Maybe Zeiss was eager to get on the Fluoride glass train before the competition?
(And that FL-move did win me over from Leica at the time...)
I tried the Victory 8/10x40:s, they were bright, but the ergonomics were not my cup of tea.
BTW, they had a die cast aluminum body (not composite as I wrote).
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Hermann
Well-known member
No. The Dialyt 10x40 in its different versions had SP prisms. As did the Dialyt 8x30. The successor of the Dialyt 10x40 however had AK prisms.
Hermann
kimmik
Well-known member
Compared to the TIR in porro, which is an uncoated surface. It would be good to hear from someone with deep knowledge of the TIR degradation vs coatings. If coatings do not degrade TIR, then half the Schmidt Pechan problems would be gone, just fully multi-coat all transmissive surfaces.
The weight issue is why I think mirror hybrid AK could make a return in the future. Then all of a sudden, traditional glass AK will be seen as old tech.
Logic is reversed here. AK and SP are non-dispersive prisms. They add no CA what so ever.
It's the longer light path in SP allowing slower objective lens, that leads to lower CA.
William Lewis
Wishing birdwatching paid the bills.
Any clue as to why Porro's generally have less ca than Sp or ak prisms with or without high flourite glass?
Does the focal length get longer due to the distance travelled through the prisms - reducing the CA or are the prisms themselves not part of the focal length calculations? I'm thinking of say the eii Vs the HG 8x30's, I can only imagine the HG has a shorter light path through the prisms than the eii?
I thought most ca is generated in the objectives - hence why that's where the high flourite glass is usually used but these would be similar in either a porro or a roof so where's the difference?
Will
Does the focal length get longer due to the distance travelled through the prisms - reducing the CA or are the prisms themselves not part of the focal length calculations? I'm thinking of say the eii Vs the HG 8x30's, I can only imagine the HG has a shorter light path through the prisms than the eii?
I thought most ca is generated in the objectives - hence why that's where the high flourite glass is usually used but these would be similar in either a porro or a roof so where's the difference?
Will
Vespobuteo
Well-known member
Yes, it was the 7x42 model that had AK-prisms. I should have trusted my gut feeling...the 10x40 were not very bright as I recall them.
Vespobuteo
Well-known member
The "Zeiss AK-prisms in 40-49mm bins"-list, so far.
1. 7x42 Dialyt BGAT 1981-2004
2. 7x45 Design Col. 1994-2000
3 8/10x40 Victory I, II 2000-2004
4. 7/8/10x42 FL 2004-2013
5. Conquest 10x40 T* 2005-2012 (made in Hungary)
6. 8/10x42 HT 2012-2018?
HT42 was the end of an almost 40 year old era it seems.
Who wants an SF(L) 8.5x48mm with AK-prisms, 96% transmission at 750 grams?
I think there might be a market...
1. 7x42 Dialyt BGAT 1981-2004
2. 7x45 Design Col. 1994-2000
3 8/10x40 Victory I, II 2000-2004
4. 7/8/10x42 FL 2004-2013
5. Conquest 10x40 T* 2005-2012 (made in Hungary)
6. 8/10x42 HT 2012-2018?
HT42 was the end of an almost 40 year old era it seems.
Who wants an SF(L) 8.5x48mm with AK-prisms, 96% transmission at 750 grams?
I think there might be a market...
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kimmik
Well-known member
Possibly from the lack of a separate focusing element.
They certainly are, see this prism tunnel diagram as an example of SP.
If you measure the length traveled by adding all the reflections, then divide by the refractive index, that is the equivalent free-air distance if the prism wasn't present.
kimmik
Well-known member
Here are the subtle differences in prism baffle, between NL42 SF32 and NV.
Swaro configures the SP prism in the conventional manner, with Pechan first, Roof second, with a baffle in between the prisms.
Leica configures the SP prism in reverse, with Roof first, Pechan second, with baffle in between the prisms. This has the effect of reducing the image circle (thus FOV) slightly, but improves the effectiveness of baffle by placing it further back.
Zeiss uses the conventional Pechan first configuration, but has two internal prism baffles, and places them at non-conventional locations - 1 at the mirror surface of the Pechan, and 2 at the first reflection of the Schmidt.
If anyone has an internal photo of Nikon EDG it would be good to see how it is baffled.
Swaro configures the SP prism in the conventional manner, with Pechan first, Roof second, with a baffle in between the prisms.
Leica configures the SP prism in reverse, with Roof first, Pechan second, with baffle in between the prisms. This has the effect of reducing the image circle (thus FOV) slightly, but improves the effectiveness of baffle by placing it further back.
Zeiss uses the conventional Pechan first configuration, but has two internal prism baffles, and places them at non-conventional locations - 1 at the mirror surface of the Pechan, and 2 at the first reflection of the Schmidt.
If anyone has an internal photo of Nikon EDG it would be good to see how it is baffled.
William Lewis
Wishing birdwatching paid the bills.
So is there any particular prism types that have an inherently longer focal length? Looking at the diagrams it looks like if anything ak prisms have one of the shortest as they don't fold the light path back on itself despite the prisms themselves being longer.
Also I know it's generally the case that Porro's need one less glass element as the moving eye piece does the focusing but I'm not sure if that can explain away it all, as an example the e2 and habicht I've owned both had similar and very low amounts of ca and no ed glass to my knowledge however the e2 does have more elements in its eye piece than the habicht which I would assume would negate the moving focusing element and lead to more ca, but it doesn't.
The other interesting thing is porro's seems to exhibit much less ca off axis than most sp and ak roofs even though the best correct it very well in the centre and some particularly well - the kowa genesis, nl, SF and fl correct it very well throughout the field in my use of them.
"Logic is reversed here. AK and SP are non-dispersive prisms. They add no CA whatsoever.
It's the longer light path in SP, allowing a slower objective lens, that leads to lower CA."
Light transmission vs. CA or AK-prisms vs. ED glass - Binoculars - Cloudy Nights
Page 1 of 2 - Light transmission vs. CA or AK-prisms vs. ED glass - posted in Binoculars: Hi guys and gals, I need a little input from the members of this fine forum. Its not that I need another bino but when was it ever a question of need? I noticed a gap in my fast growing collection and that...
William Lewis
Wishing birdwatching paid the bills.
Unless the light is split by a roof edge as such and swapped axis that way as in ak or sp prisms each prism type has to have 3 light courses within it, i.e 2 angle changes to make up the 180 degrees of angle change each prism needs to perform to make the 360 degrees needed in total.
I can't see much difference with the types from perger porro to porro in terms of how I would assume they'd perform.
But ak and sp split the light with a roof edge and sp in addition to that needs one edge per prism of the glass to be both transparent and reflective at the same time.
I think all the above is quite well known among officonardo's here!
Maybe they've coated different parts of the affected sp prism surfaces with different coatings and adjusted the light path angles accordingly?
I also think maybe more ca is a byproduct of that splitting (no roof surface in infinitely sharp) that necessitates it being minimised comprehensively before getting to the prism with a high flourite objective?
I can't see much difference with the types from perger porro to porro in terms of how I would assume they'd perform.
But ak and sp split the light with a roof edge and sp in addition to that needs one edge per prism of the glass to be both transparent and reflective at the same time.
I think all the above is quite well known among officonardo's here!
Maybe they've coated different parts of the affected sp prism surfaces with different coatings and adjusted the light path angles accordingly?
I also think maybe more ca is a byproduct of that splitting (no roof surface in infinitely sharp) that necessitates it being minimised comprehensively before getting to the prism with a high flourite objective?
John A Roberts
Well-known member
Hi kimmik,
Picking up on a few points . . .
Post #1
The type of prism doesn’t determine whether a binocular can be waterproofed (the Perger prism Leica Geovid reference).
More precisely, any prism can be used in conjunction with an internal focusing mechanism.
One early Porro prism internal focus binocular is the Kern Focalpin: Kern Focalpin
A more recent one is what I refer to for convenience as the 'MOBL' (Minox, Opticron, Bynolt and Leupold) series.
For some details and links, see post #14 at: Nikon EDG 8x42 Schmidt-Pechan prisms
And the Canon 10x42 IS (using Porro Type II prisms) is also waterproof, see posts #4 and 10 at: High end porro's
(Along with some examples of full size Porro Type I binoculars in more laterally compact, more Perger binocular like configurations.) *
Post #4
Expanding on Vespobuteo’s observation, some images and details about the Zeiss FL construction are in post #9 at: Cost vs Durability - Plastic Body
Post #8
By an 'AK in a mirror-roof configuration', perhaps the Ludewig prism used in the Leitz Amplivid? See: Leitz 6x24 not showing 'Amplivid'
Post #31
I'm not sure what you mean by the Zeiss SF32 prisms each having an internal baffle. Can you provide some more info, images or a link?
Post #34
And in terms of prism mass/ weight, what little I’ve been able to find is in post #122 and on at: Zeiss: Collection of cross-section and cutaway images
John
* The Canon 10x42 internals can be seen in post #8 at: Premium (Alpha) vs Image stabilized
Picking up on a few points . . .
Post #1
The type of prism doesn’t determine whether a binocular can be waterproofed (the Perger prism Leica Geovid reference).
More precisely, any prism can be used in conjunction with an internal focusing mechanism.
One early Porro prism internal focus binocular is the Kern Focalpin: Kern Focalpin
A more recent one is what I refer to for convenience as the 'MOBL' (Minox, Opticron, Bynolt and Leupold) series.
For some details and links, see post #14 at: Nikon EDG 8x42 Schmidt-Pechan prisms
And the Canon 10x42 IS (using Porro Type II prisms) is also waterproof, see posts #4 and 10 at: High end porro's
(Along with some examples of full size Porro Type I binoculars in more laterally compact, more Perger binocular like configurations.) *
Post #4
Expanding on Vespobuteo’s observation, some images and details about the Zeiss FL construction are in post #9 at: Cost vs Durability - Plastic Body
Post #8
By an 'AK in a mirror-roof configuration', perhaps the Ludewig prism used in the Leitz Amplivid? See: Leitz 6x24 not showing 'Amplivid'
Post #31
I'm not sure what you mean by the Zeiss SF32 prisms each having an internal baffle. Can you provide some more info, images or a link?
Post #34
And in terms of prism mass/ weight, what little I’ve been able to find is in post #122 and on at: Zeiss: Collection of cross-section and cutaway images
John
* The Canon 10x42 internals can be seen in post #8 at: Premium (Alpha) vs Image stabilized
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Pinewood
New York correspondent
Hello Kimmik,
Would you be able to show the difference between a Porro 1 and a Porro 2 binocular? The Porro 2 binoculars had some popularity with the military and with navies, manufactured by Zeiss, Leitz and Ross, and French companies, but not with Americans. Zeiss even had a civilian version, the Septarem.
Stay safe,
Arthur
Would you be able to show the difference between a Porro 1 and a Porro 2 binocular? The Porro 2 binoculars had some popularity with the military and with navies, manufactured by Zeiss, Leitz and Ross, and French companies, but not with Americans. Zeiss even had a civilian version, the Septarem.
Stay safe,
Arthur
tenex
reality-based
What I didn't understand was the part now bolded above. How do you figure that so many surfaces of SP or U prisms (the ones that actually do have TIR) have AR coatings that Porros don't? Am I missing something?
John A Roberts
Well-known member
Putting into context several points made above . . .
1) In terms of the different optical surfaces in binoculars and their main coatings
a) Transmission surfaces on both lenses and prisms, benefit from anti-reflective (A-R) coating.
It minimises the loss of light due to unwanted reflections.
Originally a single layer was used (and usually not on all suitable surfaces). Now three layers are typically used
(and camera lenses often have many more layers).
b) Prism surfaces required to be reflective - that have Total Internal Reflection - are perfect mirrors.
They don’t require coating to aid reflection, and adding an A-R coating will degrade the reflection.
c) Prism surfaces required to be reflective - that lack TIR - need an external reflective coating to provide the internal mirror function.
Traditionally a single layer of stainless steel, aluminium or silver was used.
More recently multiple layers (70+) of different dielectric coatings are used, to cumulatively achieve reflection.
d) The two roofed surfaces of roof prisms have TIR, but the splitting/ dual reflection/ recombining of the light beam,
results in a degree of de-phasing (seen as a slight loss of sharpness).
So the two roof surfaces benefit from a special phase coating.
- - - -
2) And in relation to some common prism types
i) 'Non-roofed prisms' i.e. Porro Type I and II prisms, and the Perger prism version used by Leica
All have TIR, and only benefit from coating the two transmission surfaces with A-R coating.
ii) Abbe-Koenig prisms
Also have TIR. They benefit from coating the two transmission surfaces with A-R coating,
and also from phase coating the two roof surfaces.
iii) Uppendahl and Schmidt-Pechan prisms
Each has 6 reflective surfaces. Besides the 2 roofed ones, they also have:
• Uppendahl: 1 TIR; 1 non-TIR, and; 2 combined transmission/ reflection surfaces.
• S-P prisms: 1 non-TIR, and; 3 combined transmission/ reflection surfaces (plus 1 transmission only surface).
Necessarily there’s a contradiction between the optimal coatings needed for the transmission and reflection functions of the combined surfaces.
So there’s an optical performance tradeoff, for the compactness of the prisms that’s made possible by the use of 6 verses 4 reflections.
(Whether that's significant for a manufacturer or a user . . . ?)
In terms of the limits of what we currently know, see from post #310 on at: Zeiss SFL 8x30?
The Uppendahl image is from Holger’s book (the blue dashed line indicates the mirrored surface, and the green one the two roof surfaces).
The S-P image is a well known one from Swarovski.
John
p.s. In terms of Perger prism optical performance, what we know is limited to the use in the 3rd generation Leica Geovid rangefinders.
One problem is that the additions needed to enable the RF functions, often degrade the optical transmission.
See Gijs’ work in posts #19 and 24 (specifically re the Gen 3 Geovid) at: Loss Of Brightness With 8X42 RF (HT)
1) In terms of the different optical surfaces in binoculars and their main coatings
a) Transmission surfaces on both lenses and prisms, benefit from anti-reflective (A-R) coating.
It minimises the loss of light due to unwanted reflections.
Originally a single layer was used (and usually not on all suitable surfaces). Now three layers are typically used
(and camera lenses often have many more layers).
b) Prism surfaces required to be reflective - that have Total Internal Reflection - are perfect mirrors.
They don’t require coating to aid reflection, and adding an A-R coating will degrade the reflection.
c) Prism surfaces required to be reflective - that lack TIR - need an external reflective coating to provide the internal mirror function.
Traditionally a single layer of stainless steel, aluminium or silver was used.
More recently multiple layers (70+) of different dielectric coatings are used, to cumulatively achieve reflection.
d) The two roofed surfaces of roof prisms have TIR, but the splitting/ dual reflection/ recombining of the light beam,
results in a degree of de-phasing (seen as a slight loss of sharpness).
So the two roof surfaces benefit from a special phase coating.
- - - -
2) And in relation to some common prism types
i) 'Non-roofed prisms' i.e. Porro Type I and II prisms, and the Perger prism version used by Leica
All have TIR, and only benefit from coating the two transmission surfaces with A-R coating.
ii) Abbe-Koenig prisms
Also have TIR. They benefit from coating the two transmission surfaces with A-R coating,
and also from phase coating the two roof surfaces.
iii) Uppendahl and Schmidt-Pechan prisms
Each has 6 reflective surfaces. Besides the 2 roofed ones, they also have:
• Uppendahl: 1 TIR; 1 non-TIR, and; 2 combined transmission/ reflection surfaces.
• S-P prisms: 1 non-TIR, and; 3 combined transmission/ reflection surfaces (plus 1 transmission only surface).
Necessarily there’s a contradiction between the optimal coatings needed for the transmission and reflection functions of the combined surfaces.
So there’s an optical performance tradeoff, for the compactness of the prisms that’s made possible by the use of 6 verses 4 reflections.
(Whether that's significant for a manufacturer or a user . . . ?)
In terms of the limits of what we currently know, see from post #310 on at: Zeiss SFL 8x30?
The Uppendahl image is from Holger’s book (the blue dashed line indicates the mirrored surface, and the green one the two roof surfaces).
The S-P image is a well known one from Swarovski.
John
p.s. In terms of Perger prism optical performance, what we know is limited to the use in the 3rd generation Leica Geovid rangefinders.
One problem is that the additions needed to enable the RF functions, often degrade the optical transmission.
See Gijs’ work in posts #19 and 24 (specifically re the Gen 3 Geovid) at: Loss Of Brightness With 8X42 RF (HT)
Vespobuteo
Well-known member
Thanks, excellent input as always.
A bit off-topic, on the FL-construction.
Honestly I never quite understood exactly what parts of the FL:s that are "polymer".
From the pictures it seems like all of the inner mechanical structures and tubes still are magnesium (holding lenses/prisms) and the "polymer" is more or less just the extra outer shell?
Even more confusing is that the term "aluminum housing" (typo?) is also mentioned and the figure "60%" is added?
"Casing in fibre glass-reinforced polymer for exceptional ruggedness and minimum weight"
"fibre glass-reinforced polyamide is combined with magnesium elements"
"Objective lens connection piece in high-resistance magnesium alloy"
"Lightweight, non-slip aluminium housing reinforced by glass-fiber composites (60%)"
"press-fit steel bushes for maximum stability, resistance to war and tear and uniformly smooth bridge action"
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