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charen
scholastic sledgehammer
Reged: 05/28/05
Posts: 786
Loc: New Zealand
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I am in the process of buying some Minox BD 10X58 ED BR binoculars. They are second hand but basically ‘as new’. My friendly optics dealer has let me test for a few days prior to buying them. These are not inexpensive binoculars - approx $US800 which is about half the price new where I live [New Zealand.] The new price in the US is about $US1040.
The views through the 10x58 ED’s are impressive - bright contrasty and very sharp with a well corrected field. There is very little distortion with just a small amount of astigmatism at the edge.
The objective tubes are well baffled. The FOV is a reasonable 6.2 degrees. Eye relief is excellent.
They are a solid 1490 grams / 52 oz. There are no obvious internal reflections. CA is very well suppressed and basically not existent - the lens being made of ED / Fluorite glass.
My brief impression is that they are very nice astro binoculars.
However my main concern is that a ‘moderate’ amount of prism light leakage is present - this is noted at 12, 4 and 8 o’clock. The exit pupils are perfect.
I am concerned [and surprised] at the amount of prism leakage esp. when one considers these are reasonably ‘top end’ binos.
Prism leakage is undesirable and I believe is caused by ‘inferior’ prism design. I also understand it can affect contrast and cause secondary images.
I briefly looked for prism leakage in some other roof and porro prism binoculars.
The Pentax 20x60 PCF 11 – no leakage seen, Orion Resolux 15x70 - no leakage, Oberwerk 25x100 - no leakage, Nikon Monarch 10x56 - very minimal amount observed and Meade 9x63 - moderate amount of leakage and similar to the Minox’s.
I would appreciate any ones comments or ones experience with this issue.
Is this such a concern that I should seriously re-consider buying the Minoxs ?
Thanks for any feedback.
Chris
35 binos.
80mm Cat.
WO66ED
SV NH 80mm / EQ3
Meade 8in.LX90
Edited by charen (07/01/08 03:05 AM)
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KennyJ
Reged: 04/27/03
Posts: 10146
Loc: Lancashire UK
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Chris ,
The Zeiss 7 x 42 has similar prism leaks , as have several other top end roofs I've seen .
I don't think it's anything to overly worry about , as that's what I was told , by someone who knows their stuff , when I first noticed the phenomenon , more than six years ago .
I just place a saucer under mine , to prevent the leaks from dampening the carpet ! :-)
Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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DJB
Pooh-Bah
Reged: 02/23/05
Posts: 1267
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Hi all,
As I was reading these posts, an interesting progran came on the "Science Channel. It is entitled "How do They do it." It was concerning how (they) produce modern, precise binoculars.
It is one segment on the program--about 10 minutes. It is followed by windshield wipers.
The filming took place in a Zeiss plant. The only distrubing point is how many times the segment showed folks holding the optics with bare hands and not gloves; however, gloves DID show up at least once.
It's worth a look see. Just FYI. I found it interesting.
Best regards,
Dave.
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ronharper
Pooh-Bah
Reged: 02/14/06
Posts: 1006
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I haven't a clue, but I've wondered about this, too.
Even though they have very well-blackened interiors, my Fujinon FMTs show leaks around the exit pupils when held up to a bright sky. These three binos range from excellent to only so-so in suppression of glare from bright light outside the field of view. Despite some unblackened matte-finished aluminum inside the barrel, my Leica Trinovid shows absolutely no leaks, and good suppression of such glare. So, leaks seem unrelated to internal finish and the glare problem.
If the leaked light is well outside the eye's entrance, as it is in my Fujinons, it's hard to see how it could affect the view. The issue seems to be where the light is coming from. Is this good light that should be focused into the image, or junky light from outside the field of view that we don't want to look at anyhow?
I hope somebody who understands this will explain to us.
Ron
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KennyJ
Reged: 04/27/03
Posts: 10146
Loc: Lancashire UK
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Dave ,
Thanks for that interesting aside ! :-)
I think I must be amongst the vast minority of people interested in this hobby who doesn't " have kittens " at the meagre thought of human hands actually touching glass surfaces !
Some poeple seem to liken such an act to having eating rat poison !
Chris and Ron ( and Dave for that matter )
Given all the members here I KNOW own top brand roof prism binoculars , I can hardly believe that not a single one of them has contributed to this thread .
I think EVERY top roof bino I've ever seen has at least one DISTINCT crescent - shaped " prism leak " clearly visible in the exit - pupil .
More often TWO !
They are ALWAYS perfect little crescent shapes , with the same shapes through each prism reflecting the same colour as each other , but not the same colour as the smaller shapes ( if and when present )
Surely I can't be the only person to have noticed this ?
Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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DJB
Pooh-Bah
Reged: 02/23/05
Posts: 1267
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Hi Kenny,
A good reply to an interesting thread. I have many kittens and one dog--so I use rubber surgical gloves when handelng optics, followed by a good cleaning of said optics.
I agree that the topic has been somewhat overlooked, don't you think?
Best regards,
Dave.
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ronharper
Pooh-Bah
Reged: 02/14/06
Posts: 1006
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Kenny,
I guarantee the Trinovid is sans leak, and I have seen other users of this series remark on it as well. Not that it amounts to much!
I think what is happening with your Zeiss is light is being refracted by the oils from a fingerprint on the Abbe-Konig prisms, probably left by a worker who had some great sausage for lunch and didn't wash up before entering the assembly room.
Ron
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KennyJ
Reged: 04/27/03
Posts: 10146
Loc: Lancashire UK
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You could be right there , Ron .
Every now and again , I do get a distinct whiff of sizzling sausage whilst using the Zeiss , but had always put it down to the incessant barbecuing activities taking place across the road !
Regards
Kenny
--------------------
If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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GlennLeDrew
professor emeritus
Reged: 06/18/08
Posts: 624
Loc: Ottawa, Ontario, Canada
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I don't own roof prism binos, so my thoughts are speculative...
How far from the edge of the exit pupil are these leaks? Might they be sufficiently far away that they will be outside your eye's fully dilated pupil? If that's the case, it's probably not worth worrying about.
It would be interesting to see if these leaks are from off-axis light coming through the objectives, or instead light going into the eyepieces from *behind* and bouncing around in the prisms. If the latter, your eyes will naturally block this.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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charen
scholastic sledgehammer
Reged: 05/28/05
Posts: 786
Loc: New Zealand
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Hi thanks for the comments everyone.
The prism leakage is very similar to the photo attached. The leakages are noted at 12, 8 and 4pm
The leakage is seen when viewing the exit pupils several inches away looking at bright daylight
This form of leakage would indicate [I strongly assume] is from the light coming in via of axis light from the front objective lens.
I am still left wondering how detrimental this is for the image quality and secondly for the build quality.
I am still assuming ‘any form’ of prism leakage is a negative and will affect the image even thought it is not obvious in the case of the Minox's
Of course this is difficult to quantify as I do not have a pair that does not show prism leakage for comparison.
This photo is taken from the below site at ‘Fans Binocular Collection’
Several other forms of prism leakage are also displayed.
http://fantao.home.att.net/information.htm
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35 binos.
80mm Cat.
WO66ED
SV NH 80mm / EQ3
Meade 8in.LX90
Skywatcher Equinox ED120 / Goto HEQ5.
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ronharper
Pooh-Bah
Reged: 02/14/06
Posts: 1006
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I did a search, and found a good discussion of this issue from back in 2004. I regret that I seem to have lost my ability to give a long url a neatly-named link, and apologize for messing up the appearance of this thread on everybody's computer, but I think the information contained herein will be worth that inconvenience. So here goes:
prism leakage thread
Edited by EdZ (07/03/08 01:08 PM)
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