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The Cameraland NY Mystery Binocular (1 Viewer)
- Thread starter Steve C
- Start date
FrankD
Well-known member
NW,
Henry would be the one to accurately answer that type of question. I would have a hard time believing that Swarovski would use an entirely conventional prism design.
..and, FWIW, I have decided to sell both of my ELs and the SLC. I just cannot justify the cost when comparing the optical performance of them and the Promaster. (Watch Ebay tomorrow night if you do not believe me
) Yes, the Promaster is that good. I plan on ordering an 8x42 from Doug come Tuesday morning.
...I would love to see them come out with an 8x32 version as well.
Now, I look forward to seeing if Henry made the trip to Camcor. If they had one in stock I would love to hear his impressions of them optically.
Henry would be the one to accurately answer that type of question. I would have a hard time believing that Swarovski would use an entirely conventional prism design.
..and, FWIW, I have decided to sell both of my ELs and the SLC. I just cannot justify the cost when comparing the optical performance of them and the Promaster. (Watch Ebay tomorrow night if you do not believe me
) Yes, the Promaster is that good. I plan on ordering an 8x42 from Doug come Tuesday morning. ...I would love to see them come out with an 8x32 version as well.
Now, I look forward to seeing if Henry made the trip to Camcor. If they had one in stock I would love to hear his impressions of them optically.
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Did I read that right? Two-and-a-half turns?
From what I'm reading, I'd buy the 8x42 in a heartbeat, but depth of field and relatively fast focus would be a must in a general purpose binocular. If they get that fixed, I'll buy one.
Selling those new ELs, Frank...dang. Nothing is ever going to justify their price from a practical perspective, but that's still my dream binocular!
From what I'm reading, I'd buy the 8x42 in a heartbeat, but depth of field and relatively fast focus would be a must in a general purpose binocular. If they get that fixed, I'll buy one.
Selling those new ELs, Frank...dang. Nothing is ever going to justify their price from a practical perspective, but that's still my dream binocular!
Kevin Purcell
Well-known member
Apologies this is a bit rambling ...
Wow, that's a commitment, Frank!
The only doubts I have are service/warranty (though Doug is said to stand behind his bins).
http://promaster.com/products/produ...atName=&CatID=60&Page=Cat&sm=sm2_C_Binoculars
I see this on the Promaster bins:
So that seems reasonable so long as their customer service works.
Has Doug set a price yet?
I second (and Tero will third, I'm sure) the 8x32 comment. I'd love to see a similar set in 8x32. I doubt they need ED for these either (after all the Zeiss Conquest doesn't use ED or FL or similar "fancy" glass for the 300mm class product.
But a bit of searching shows they already have something in the right ballpark. Currently they make the ProMaster Infinity Elite 8 x 32 (Promaster #6944) that retails for $149 (or $159 at Wolfes).
http://promaster.com/products/produ...culars&sm=sm2_601&dir=&page=PROD&product=6944
Power: 8X
Objective Lens Diameter: 32mm
Type of Prism: BAK4 Roof
Prism Coating: Silver and phase coated
Number of Lens: 8 elements in 6 groups
Lens Coating: TRANSBRIGHT™ and full broadband multicoatings
Focus System: Internal center focusing
Exit Pupil Diameter: 4.1mm
Eye Relief: 14.7mm
Field of View: 8.13° - 426 ft. @ 1000 yds.
Minimum Focusing Distance: 6.56’/2M
Diopter System: Left eyepiece -±4
Waterproof: 1.5m for 3 minutes
Weatherproof: Nitrogen filled fog proof
Weight: 18.6 oz.
The blurb also mentioned REPELLAMAX™ element repellent on the external optics. So that's all the same coatings as the top end bin. I wonder how the quality is?
They used to(?) make Promaster Infinity 7x32 Binocular (Promaster #8654). Of course this begs the question has anyone tried the Promaster Infinity 7x32 Binocular. The specs don't look that bad. It's x7 for a start!
http://wolfes.com/eshop/cart.php?target=product&product_id=2699&category_id=340
# Field of View - 389' @ 1000 Yards
# Eye Relief - 17mm
# Prism - Silver Coated BAK-4 Porro
# Minimum Focus Distance - 9.8'
# Waterproof, Nitrogen filled
# Includes deluxe case
Silver Coated prisms too ... that's interesting. But there' is no mention of phase coating but other ads mention "Fully Broadband Multicoated". And it's only $99. So it's either it's a steal or it's another fully multicoated non-PC bin.
I see Tero commented on Promaster back in 2004. I wonder which bin he tried?
http://www.birdforum.net/showthread.php?t=27028
Of course that was 4 years ago for an unspecified model. How things change. Perhaps it's time to revisit their optics.
I note here
http://promaster.com/products/produ...Scopes&sm=sm2_602&dir=&page=PROD&product=1180
They are making an ED scope too: the "PROMASTER INFINITY ELX 65MM ED"
[...] ..and, FWIW, I have decided to sell both of my ELs and the SLC. I just cannot justify the cost when comparing the optical performance of them and the Promaster. (Watch Ebay tomorrow night if you do not believe me
...I would love to see them come out with an 8x32 version as well.
Now, I look forward to seeing if Henry made the trip to Camcor. If they had one in stock I would love to hear his impressions of them optically.
Wow, that's a commitment, Frank!
The only doubts I have are service/warranty (though Doug is said to stand behind his bins).
http://promaster.com/products/produ...atName=&CatID=60&Page=Cat&sm=sm2_C_Binoculars
I see this on the Promaster bins:
So that seems reasonable so long as their customer service works.
Has Doug set a price yet?
I second (and Tero will third, I'm sure) the 8x32 comment. I'd love to see a similar set in 8x32. I doubt they need ED for these either (after all the Zeiss Conquest doesn't use ED or FL or similar "fancy" glass for the 300mm class product.
But a bit of searching shows they already have something in the right ballpark. Currently they make the ProMaster Infinity Elite 8 x 32 (Promaster #6944) that retails for $149 (or $159 at Wolfes).
http://promaster.com/products/produ...culars&sm=sm2_601&dir=&page=PROD&product=6944
Power: 8X
Objective Lens Diameter: 32mm
Type of Prism: BAK4 Roof
Prism Coating: Silver and phase coated
Number of Lens: 8 elements in 6 groups
Lens Coating: TRANSBRIGHT™ and full broadband multicoatings
Focus System: Internal center focusing
Exit Pupil Diameter: 4.1mm
Eye Relief: 14.7mm
Field of View: 8.13° - 426 ft. @ 1000 yds.
Minimum Focusing Distance: 6.56’/2M
Diopter System: Left eyepiece -±4
Waterproof: 1.5m for 3 minutes
Weatherproof: Nitrogen filled fog proof
Weight: 18.6 oz.
The blurb also mentioned REPELLAMAX™ element repellent on the external optics. So that's all the same coatings as the top end bin. I wonder how the quality is?
They used to(?) make Promaster Infinity 7x32 Binocular (Promaster #8654). Of course this begs the question has anyone tried the Promaster Infinity 7x32 Binocular. The specs don't look that bad. It's x7 for a start!
http://wolfes.com/eshop/cart.php?target=product&product_id=2699&category_id=340
# Field of View - 389' @ 1000 Yards
# Eye Relief - 17mm
# Prism - Silver Coated BAK-4 Porro
# Minimum Focus Distance - 9.8'
# Waterproof, Nitrogen filled
# Includes deluxe case
Silver Coated prisms too ... that's interesting. But there' is no mention of phase coating but other ads mention "Fully Broadband Multicoated". And it's only $99. So it's either it's a steal or it's another fully multicoated non-PC bin.
I see Tero commented on Promaster back in 2004. I wonder which bin he tried?
http://www.birdforum.net/showthread.php?t=27028
Of course that was 4 years ago for an unspecified model. How things change. Perhaps it's time to revisit their optics.
I note here
http://promaster.com/products/produ...Scopes&sm=sm2_602&dir=&page=PROD&product=1180
They are making an ED scope too: the "PROMASTER INFINITY ELX 65MM ED"
Bob A (SD)
Well-known member
Kevin,
Look around here a bit and you'll find several older threads where folks took a look at those much cheaper Promasters. Bottom line is that they certainly didn't ignite any enthusiasm unlike these much more expensive ED pieces.
FrankD,
I really want to tease you on how many SLCs have made it through your door and out again but.... I take it you're keeping either your FL or the Meopta. Or did you already part with the later?
Frankly I could really loose a few here for insufficient usage (Yosemite, Carson, and Orion to start with). Ah well.....
Look around here a bit and you'll find several older threads where folks took a look at those much cheaper Promasters. Bottom line is that they certainly didn't ignite any enthusiasm unlike these much more expensive ED pieces.
FrankD,
I really want to tease you on how many SLCs have made it through your door and out again but....
I take it you're keeping either your FL or the Meopta. Or did you already part with the later?Frankly I could really loose a few here for insufficient usage (Yosemite, Carson, and Orion to start with). Ah well.....
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Kevin Purcell
Well-known member
But those comments are about the ProMaster products for 3 or 4 years ago. As ProMaster are a brand and sell OEMed products it might even be that the current range of ProMaster Elite bins are designed and made by a different OEM from the previous ones.
Plus Chinese optical manufacture has moved on in the past few years. The technical product quality is significantly better than just a few years ago.
For example, in 2006 Tero was actually impressed by ProMaster (which is saying something for his "almost a Sporter" Finnish outlook )
http://www.birdforum.net/showpost.php?p=508213&postcount=8
And it's quite clear, as you say, several others are impressed by the ELX, both here and on the 24campfire.com threads. So it seems reasonable to check out the other bins which seem to be coming from the same design house and the same OEM with the same coatings minus the ED objectives (and in different sizes for those that like 32mm objectives).
Perhaps all these are sharing some of the same design. They are all 8 elements in 6 groups for the top end and bottom end Elites: 2 in the objective, 1 or two in the focuser (probably 1 though 2 would control CA a bit better) and 4 or 5 in th eye piece (again 5 elements would control stray color better especially with a wide FOV and long ER). Of course that's just a crude measure (it depends how they optimized the whole system). But I suspect they share some parts.
A week ago I would have written off Promaster as another OEM rebadging shop. Perhaps they are but if they're rebadging good stuff then I'd like to know.
And that takes us full circle to Steve's comments about blind tests.
So as usual looking through the bins and performing some empirical tests is the best way to find out the answer. And there are enough binocuholics around here who would rise to this sort of a challenge
Plus Chinese optical manufacture has moved on in the past few years. The technical product quality is significantly better than just a few years ago.
For example, in 2006 Tero was actually impressed by ProMaster (which is saying something for his "almost a Sporter" Finnish outlook
)http://www.birdforum.net/showpost.php?p=508213&postcount=8
And it's quite clear, as you say, several others are impressed by the ELX, both here and on the 24campfire.com threads. So it seems reasonable to check out the other bins which seem to be coming from the same design house and the same OEM with the same coatings minus the ED objectives (and in different sizes for those that like 32mm objectives).
Perhaps all these are sharing some of the same design. They are all 8 elements in 6 groups for the top end and bottom end Elites: 2 in the objective, 1 or two in the focuser (probably 1 though 2 would control CA a bit better) and 4 or 5 in th eye piece (again 5 elements would control stray color better especially with a wide FOV and long ER). Of course that's just a crude measure (it depends how they optimized the whole system). But I suspect they share some parts.
A week ago I would have written off Promaster as another OEM rebadging shop. Perhaps they are but if they're rebadging good stuff then I'd like to know.
And that takes us full circle to Steve's comments about blind tests.
So as usual looking through the bins and performing some empirical tests is the best way to find out the answer. And there are enough binocuholics around here who would rise to this sort of a challenge
Steve C
Well-known member
Owen,
You did read that right: Two and one half turns. That coupled with the fact that it focuses opposite to my other binoculars made me wonder for a second just what in the world was going on. I talked with the head guy at Cameraland and he does not think an immediate change is in the cards. The first production run is set. As to what happens later is anybody's guess. After use and you get used to it it is not as bad as it might seem. I am making a guess, but I sort of think it is intended to be a dual range sort of focus, one rate close in and another rate further out. I did not have time to go hit the local wildlife refuge for any proper birding, but I did get out and do what I could. The rate when focusing at any particular distance actually does not seem so slow. But try to go from a Hawk or Waterfowl way out there to a little bird close in and then it seems to take forever. For somebody who would use these as their sole binocular, they would accomodate pretty fast. However, I'd like to see it just half of what it is. Also It began to dawn on me that the focus depth improved dramatically as distance increased.
I am really considering buying one to give it a full week or two real use. The image and resolution in relation to the price paid is a powerful pull for now.
You did read that right: Two and one half turns. That coupled with the fact that it focuses opposite to my other binoculars made me wonder for a second just what in the world was going on. I talked with the head guy at Cameraland and he does not think an immediate change is in the cards. The first production run is set. As to what happens later is anybody's guess. After use and you get used to it it is not as bad as it might seem. I am making a guess, but I sort of think it is intended to be a dual range sort of focus, one rate close in and another rate further out. I did not have time to go hit the local wildlife refuge for any proper birding, but I did get out and do what I could. The rate when focusing at any particular distance actually does not seem so slow. But try to go from a Hawk or Waterfowl way out there to a little bird close in and then it seems to take forever. For somebody who would use these as their sole binocular, they would accomodate pretty fast. However, I'd like to see it just half of what it is. Also It began to dawn on me that the focus depth improved dramatically as distance increased.
I am really considering buying one to give it a full week or two real use. The image and resolution in relation to the price paid is a powerful pull for now.
FrankD
Well-known member
Lots of comments for me to comment on....
I saw that too and spoke to Doug. I should have a demo in my hands next week for review. Look for a comparison between it and the Pentax 65 ED A.
Bob A,
That woudl be two SLCs that have come and are about to go. Both 7x42s. I almost bit the bullet and bought an 8x30 but that pinky focusing has me a bit indecisive. These will be the only two ELs I have bought and sold. The Meopta was returned about a week after I purchased it. Truthfully though, other than the CA in high contrast situations that bin also competes very well with the top end.
Marcus,
I must admit that I laughed (good naturedly) when I first read your post. I do not think you will be disappointed with them. As I said in my earlier posts, optically these binoculars are probably the closest thing I have seen to the Alpha bins I have owned. They most certainly compete optically with the ELs in terms of centerfield apparent sharpness, color, contrast and are actually better in terms of controlling color fringing. The slightly smaller apparent field of view (60 vs 64 degrees) is noticeable but at 393 feet for a full sized 8x I would hardly call it restrictive.
Ergonomically and mechanically it could use some improvements. As I said the focus on my unit has some play in it.....the open bridge could be a little bit longer between supports for better finger placement and the eyecups could be a bit more comfortable but, in my opinion, the optical quality more than makes up for the physical/mechanical deficits at least from my perspective. To put it in plain terms, imagine the Vortex Razor body with Monarch quality eyecups and armoring but with high end quality optics.
FWIW, I do not believe Doug set a price yet but I do know he has some in stock. I would guess either right at the $500 price point or slightly less. I just don't know how anyone could turn that down unless you already own several high end bins. If you are fishing for a steal in terms of price versus perfomance and you are in the market for a new bin then you really deserve to give this bin a try.
As for the focus, I believe Steve hit the nail on the head. I do not notice much if any problem with the focusing speed at moderate to long ranges. Going from fairly close focus (10-15 feet) and then focusing out to 60-70 feet does take more time than normal but it also gives you a bit more control of the sharpest focus. I never owned an original EL but I wonder if this Promaster focus is similar to it.
I saw that too and spoke to Doug. I should have a demo in my hands next week for review.
Look for a comparison between it and the Pentax 65 ED A.Bob A,
That woudl be two SLCs that have come and are about to go. Both 7x42s. I almost bit the bullet and bought an 8x30 but that pinky focusing has me a bit indecisive. These will be the only two ELs I have bought and sold. The Meopta was returned about a week after I purchased it. Truthfully though, other than the CA in high contrast situations that bin also competes very well with the top end.
Marcus,
I must admit that I laughed (good naturedly) when I first read your post. I do not think you will be disappointed with them. As I said in my earlier posts, optically these binoculars are probably the closest thing I have seen to the Alpha bins I have owned. They most certainly compete optically with the ELs in terms of centerfield apparent sharpness, color, contrast and are actually better in terms of controlling color fringing. The slightly smaller apparent field of view (60 vs 64 degrees) is noticeable but at 393 feet for a full sized 8x I would hardly call it restrictive.
Ergonomically and mechanically it could use some improvements. As I said the focus on my unit has some play in it.....the open bridge could be a little bit longer between supports for better finger placement and the eyecups could be a bit more comfortable but, in my opinion, the optical quality more than makes up for the physical/mechanical deficits at least from my perspective. To put it in plain terms, imagine the Vortex Razor body with Monarch quality eyecups and armoring but with high end quality optics.
FWIW, I do not believe Doug set a price yet but I do know he has some in stock. I would guess either right at the $500 price point or slightly less. I just don't know how anyone could turn that down unless you already own several high end bins. If you are fishing for a steal in terms of price versus perfomance and you are in the market for a new bin then you really deserve to give this bin a try.
As for the focus, I believe Steve hit the nail on the head. I do not notice much if any problem with the focusing speed at moderate to long ranges. Going from fairly close focus (10-15 feet) and then focusing out to 60-70 feet does take more time than normal but it also gives you a bit more control of the sharpest focus. I never owned an original EL but I wonder if this Promaster focus is similar to it.
Alexis Powell
Natural history enthusiast
Ha! Not necessarily; this sort or enthusiasm for one or another model, coupled with buying and returning/selling several other recently acquired models of excellent binos is FrankD's modus operandi (no criticism implied or disrespect intended Frank, just want to help folks place this bold move on your part into historically informed perspective
--AP
Kevin Purcell
Well-known member
I believe this obligates you to write a review. Rule 42 subsection 2 paragraph (c) of the BirdForum Rules. I'm looking forward to it
FrankD
Well-known member
I would like to hear your comments as well Marcus. Maybe I am being a bit premature but I think alot of folks have been waiting for that mid-price roof prism glass that would finally stand in the company of the big boys and not blink. (Yeah, I know binoculars don't blink but...) This may very well be that glass.
To elaborate a little further....
...I continue to spend more and more time using this binocular exclusively. This morning my son and I went up to the local hawkwatch to see how it compared under some of the most demanding conditions, optically, that I am aware of. I say this particular activity is optically demanding because it has been my experience that hawkwatching at this locale really shows a binocular's optical faults. Color fringing, field curvature, lack of sharpness....are all fairly apparent in this activity.
Well, I half expected this binocular to look less than stellar when placed in this environment. I was pleasantly surprised. Unlike many other excellent glasses out there, including a few Alphas, this binocular displays a very low level of color fringing. As with the Zeiss FL and also the Nikon SE the image looks extremely sharp. The smallest details (windows on houses several miles away, windmills on top of mountains dozens of miles away, individual trees in forest groves miles distant) jump out at you. The distant horizon is usually the easiest way to notice color fringing in any binocular. I can easily move the horizon-line up and down in the field of view of any binocular to see how much color fringing it displays. With the Promaster the purple and green lines are visible along the horizon but only in the outer third of the image. In addition they are very thin in width. The FL controls color fringing better but the level displayed in the Promaster is quite good in my opinion.
I was also switching from distant focus to relatively close focus because of warblers in some of the nearby trees. The slower focusing rate was hardly noticeable and, again, the slower speed seemed to give me slightly more control over getting the sharpest image.
I had a few extremely experienced birders up there with me today. One was using the Swaro EL 8.5x42s (though he regularly used the 10x50 SLCs). The other was toting a pair of the Leica BNs (not sure if they were the 8 or 10xs). I showed the Promasters to the Swaro guy first. After looking through them for just a few seconds his first comment was "These are definitely sharp...". He was experienced enough with his own bins' specs to note that the Promaster had the same field of view and weighed about the same. Both of which he commented on. He asked the usual set of questions..."Who makes it and how much does it cost?". I filled in the blanks and he just stared a bit like I was joking.
After the second gentleman came up to the site the first hawkwatcher asked for the bins again so that he could show them to the new arrival. The Leica user studied them intensely for about five minutes before he was told their cost and their name. His first response was "Do they make a 32 mm model?". He too was impressed by their performance even before being told the price.
John T. knows the two gentleman I am referring to and he can verify that they know their optics. To hear those kind of comments from these gentleman definitely provided a sense of vindication of my own experiences. I still think I am imaging seeing such an excellent image from these bins.
More to follow.
To elaborate a little further....
...I continue to spend more and more time using this binocular exclusively. This morning my son and I went up to the local hawkwatch to see how it compared under some of the most demanding conditions, optically, that I am aware of. I say this particular activity is optically demanding because it has been my experience that hawkwatching at this locale really shows a binocular's optical faults. Color fringing, field curvature, lack of sharpness....are all fairly apparent in this activity.
Well, I half expected this binocular to look less than stellar when placed in this environment. I was pleasantly surprised. Unlike many other excellent glasses out there, including a few Alphas, this binocular displays a very low level of color fringing. As with the Zeiss FL and also the Nikon SE the image looks extremely sharp. The smallest details (windows on houses several miles away, windmills on top of mountains dozens of miles away, individual trees in forest groves miles distant) jump out at you. The distant horizon is usually the easiest way to notice color fringing in any binocular. I can easily move the horizon-line up and down in the field of view of any binocular to see how much color fringing it displays. With the Promaster the purple and green lines are visible along the horizon but only in the outer third of the image. In addition they are very thin in width. The FL controls color fringing better but the level displayed in the Promaster is quite good in my opinion.
I was also switching from distant focus to relatively close focus because of warblers in some of the nearby trees. The slower focusing rate was hardly noticeable and, again, the slower speed seemed to give me slightly more control over getting the sharpest image.
I had a few extremely experienced birders up there with me today. One was using the Swaro EL 8.5x42s (though he regularly used the 10x50 SLCs). The other was toting a pair of the Leica BNs (not sure if they were the 8 or 10xs). I showed the Promasters to the Swaro guy first. After looking through them for just a few seconds his first comment was "These are definitely sharp...". He was experienced enough with his own bins' specs to note that the Promaster had the same field of view and weighed about the same. Both of which he commented on. He asked the usual set of questions..."Who makes it and how much does it cost?". I filled in the blanks and he just stared a bit like I was joking.
After the second gentleman came up to the site the first hawkwatcher asked for the bins again so that he could show them to the new arrival. The Leica user studied them intensely for about five minutes before he was told their cost and their name. His first response was "Do they make a 32 mm model?". He too was impressed by their performance even before being told the price.
John T. knows the two gentleman I am referring to and he can verify that they know their optics. To hear those kind of comments from these gentleman definitely provided a sense of vindication of my own experiences. I still think I am imaging seeing such an excellent image from these bins.
More to follow.
henry link
Well-known member
Swarovski uses two different arrangements of the Schmidt-Pechan prism. The SLC uses the same arrangement as Zeiss (the models that use Schmidt-Pechan) and Leica: the Schmidt prism comes first and the roof is in the Pechan prism. In the EL the Pechan prism comes first and the roof is in the Schmidt prism as in the Nikon LX L.
Kevin Purcell
Well-known member
For those that are having a problem visualizing this (like me) I refer to the diagram in Wikipedia
http://en.wikipedia.org/wiki/Roof_prism shows the roof idea clearly in a pentaprism for those in need of a refresher.
And this article shows the "standard" layout with the Schmidt prism on top (BTW, I wrote most of the text in this article so let me know of any errors).
http://en.wikipedia.org/wiki/Schmidt-Pechan_prism
So Henry is saying in the alternative Sawro design the roof is moved from the top of the top prism to the bottom of the bottom prism (and the flat surface moves from the bottom of the bottom to the top of the top prism) and the whole prism assembly is mounted "backwards" in the light path (i.e. the light comes in on the right and exits to the left in the Wikipedia diagram. Is that right?
Of course the next question is: why? What's the win in this design? The only thing I can see is it points the "wide" end of the prism at the objective. Does it make for a better fit in, or perhaps a smaller, tube?
And to nitpick (I shouldn't do this with Henry as I'm sure he's forgotten more than I know about optics) the Pechan prism is actually a two prism composite (the top prism has a planar mirrored surface not a roof). From the MIL HBK 141 on optics design.
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henry link
Well-known member
Kevin,
You're quite right. I shouldn't have called the second prism a Pechan prism. One name I've seen applied to that prism type is semi-pentaprism. The diagram in the Wikapedia article shows the arrangement as it's done in the ELs and Nikon LX L, with the semi-pentaprism first and the Schmidt with roof second. Leica, Zeiss and the SLCs would send the light through this diagram backwards and move the roof to the bottom semi-pentaprism.
Are you sure the roof faces need mirror coating? In discussions here in the past people who have looked at the actual prisms have reported that there are no mirror coatings on the roof surfaces because the roof angles themselves provide the critical angle for TIR.
Henry
You're quite right. I shouldn't have called the second prism a Pechan prism. One name I've seen applied to that prism type is semi-pentaprism. The diagram in the Wikapedia article shows the arrangement as it's done in the ELs and Nikon LX L, with the semi-pentaprism first and the Schmidt with roof second. Leica, Zeiss and the SLCs would send the light through this diagram backwards and move the roof to the bottom semi-pentaprism.
Are you sure the roof faces need mirror coating? In discussions here in the past people who have looked at the actual prisms have reported that there are no mirror coatings on the roof surfaces because the roof angles themselves provide the critical angle for TIR.
Henry
Kevin Purcell
Well-known member
No, I am not sure. I'd love to get this clarified.
I did some rough calculations that seemed to indicate that TIR wouldn't work off the roof surfaces but trying to do a 3D calculation on the back on an envelope and guessing at beam widths means I could just be mistaken.
In one optics book I saw it pointed out that the "bottom" surface of the first semi-pentaprism is mirrored. Plus in the original Pechan prism the flat top surface of the upper prism (where the roof is in the SP) is mirrored (that's from MIL HBK 141).
But if people have pulled an SP prism apart and can give first hand knowledge (or a citation ... I amazed I haven't found one that indicates the mirroring!) I'd love to hear/see more.
The pictures of a SP on zbirding are difficult to interpret (as are any pictures of a mirror!).
http://www.zbirding.info/zbirders/blogs/sing/archive/2006/08/09/189.aspx
And Steve Ingraham does say (my emphasis):
Steve Ingraham said:
I think part of my problem is confusing the informal use of "roofs" to mean roof prism rather than "roof surface".
EDIT: I answer my own question ... with the help of the University of Arizona (nice slides of a range of different prisms with tunnel diagrams). As they say "Note only one surface is mirrored". The lower surface of the first prism.
http://www.optics.arizona.edu/ot/opti202/Misc/202 Prisms.pdf
That blows my explanation of why my 8x42 Diamondbacks are so "dim" in twilight (i.e. less bright) than my smaller 8x32 porros. With three mirrored reflections it made more sense!
I'll fix the WP article. Thanks for the push, Henry!
EDIT 2:
The first prism is apparently also called a 45 degree Bauernfeind prism this is mentioned on page 358 of "Opto-mechanical systems design" By Paul R. Yoder (on Google Books). He also comments about moving the roof from the Schmidt prism to the bottom Bauernfeind prism. He say's "it lends itselft to packaging in a conveniently shaped housing configuration". I guess that's why Swaro do it.
http://books.google.com/books?id=uk...arch_s&sig=ACfU3U2ggEpONHbBFR0Gpr9AjJiA0cTU1A
One page 395 he shows how even the Germans mount SP prisms with urethane glue. Anyone recognize the bin? The trick is in where the glue is applied
http://books.google.com/books?id=uk...X&oi=book_result&resnum=4&ct=result#PPT427,M1
Last edited:
Kevin Purcell
Well-known member
See this paper "Progress in Binocular Design" from Konrad Siel at Swaro in 1991. Very interesting.
http://www.optics.arizona.edu/optomech/references/papers/Seil 1991.pdf
http://www.optics.arizona.edu/optomech/references/papers/Seil 1991.pdf
