Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I'm looking for some clarification on prism shelf vignetting issue. I've been looking through the vignetting posts and couldn't find anything that deals with the following questions:
When checking thru the objective end of the binos for prism shelf vignetting, how should the vignetted exit pupil be aligned? Should the exit pupil edge that can't be seen (estimated position of the hidden part) be lined up with edge of the objective or is the visible vignetted edge of the cat's eye shape used?
It seems to me that the hidden edge of the exit pupil be used so the cat's eye shape should appear towards the center a little bit and not lined up at the edge of the objective. If the binos were totally unobstructed (or the obstruction removed) then you would see what would be the hidden part of the exit pupil at the edge of the objective.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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Craig,
I don't think this would be something you could look at with a degree of accuracy that it make any difference to make an attempt to pick out the edge of the exit pupil or the hidden part of the exit pupil.
Maybe if you could describe what it is you are trying to do? I've seen some of the photos recently that attempt to show the difference.
Looking down the objective and noticing vignette in the exit pupil is what led to using a laser light and actually taking measurements of the projected exit pupil.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I'm not looking for accuracy, just a rough idea of how much cat's eye vignetting there is. I've drawn up a couple of details showing what I'm trying to accomplish. Hopefully they're not too big to post.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
Edited by Craig Simmons (10/01/04 10:17 AM)
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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In the details, the amount of vignetting visible depends on how you sight the exit pupil. It will show more vignetting if you use the cat's eye edge instead of the estimated (hidden) exit pupil edge.
I think I've got the vignetted portions switched in the figures. there should be more in fig B than fig A.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
Edited by Craig Simmons (09/28/04 11:03 AM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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based on the pictures above Fig A doesn't tell you anything. Fig B at least lines up objective edge with prism shelf edge and shows you the result. But neither of these will give you the same results that you would get from using a laser at the edge of the objective.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I agree the laser is the accurate way to determine the vignetting, I will have to try that method.
Why wouldn't Fig A show the vignetting accurately? If the obstruction (prism shelf housing) were removed wouldn't the exit pupil be sighted at the edge in an unobstructed design?
I may be misinterpreting what I see in my binos.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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I think what that shows you is the resultant exit pupil when the prism is lined up with some point about 5 to 10mm in from the edge of the objective.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I'm not sure I understand yet. Here's some cutaway diagrams showing obstructed and unobstructed light paths that I think is the situation. In both cases the edge of the exit pupil is roughly lined up with and tangent to the edge of the objective and light cone. In the obstructed diagram the prism shelf intrudes into the light path and creates the cat's eye shape as seen from the edge like the situation in Figure A. In the unobstructed diagram the perspective is the same but the prism shelf housing has been removed from the light path and the exit pupil is round. It seems to me that if you line the exit pupil edge up with objective edge then that show you the amount of vignette. Figure B seems to show a perspective that is too far outward and the exit pupil would still be partially not visible (blocked by the bino objective holder) even if the prism shelf obstruction were removed.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
Edited by Craig Simmons (10/01/04 10:17 AM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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These drawings don't really depict what's going on in the light path. There isn't anything inside the binocular that is getting out in front of the prism, unless there may be a binocular with a very poorly designed internal baffle. I haven't seen any that that bad.
There is not doubt the exit pupil is being cut, but it's not clearly shown by either of these drawings. All the light from the objective enters the front prism shelf opening. After that numerous things go on that result in a cut off exit pupil. probably one thing that is happening is refraction in the prism, all the light coming in gets bent and may not travel the path you would expect before it exits.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I thought the prism shelf was causing the cat's eye shape. I guess I've got this all mixed up.
A few minutes later....
I just re-read your opening "Viginette in all binos" post. I see you say that it's the baffles that are causing the cat's eye shape and vignette. I could have sworn I read something in that thread about the prism shelf housing cutting off the light. I've been babbling about prism shelf vignette for the past week on several forums. I feel like a total *bleep*.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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That vignette thread was probably 20 posts of discovery before we got down to what may really be going on. If you read down maybe 10 posts into the thread yopu find a whole long post of mine where I doubted everything I did up to that point. Without reading that whole thread, you will miss the entire discovery process.
Makes me think there are probably a dozen posts in there that I should go back and erase.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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I need to re-read that thread completely, carefully and pay attention as to how it evolved and what was discovered. Don't erase the posts yet. 
Thanks for this discussion and the time you've spent on this issue with me. It helped straighten out my misconceptions.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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maybe a better way to handle it would be to go into each post that was discovery and edit it with a single sentence at the top stating such.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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BillC
on a new path
Reged: 06/04/04
Posts: 2100
Loc: Washington, USA
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>>>That vignette thread was probably 20 posts of discovery before we got down to what may really be going on.<<<
If any prism shelf is vignetting, the image is not as good as it should be. Binos have a sharp field stop at prime focus. Prism shelves are not sharp and scatter. What bino is stopped at the shelf?
Cheers,
Bill
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William J. Cook, Chief Opticalman, USNR-Ret.
Founding Editor, Amateur Telescope Making Journal
20-year vet. of Captain's Nautical Supplies, Optics Dept. Mgr.
Optics Machanic, WG11-3306, Ft. Lewis, Tacoma,WA
Yata, Yata, Yata . . .
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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Probably not very many. I'll have to chalk this one up as an embarrassing learning experience.
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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Bill Cook's posts in the Vignette thread go a long way toward explaining the use and placements of stops.
Comments on use of stops
More on stops
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Craig Simmons
Carpal Tunnel
Reged: 12/10/03
Posts: 1502
Loc: Falls Church, VA
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Good commentaries by Bill on why binos have vignetted designs and specific optical components. I sat down last night and this morning and read most of your "Vignette" thread. Much clearer to me now. I'm looking forward next month to seeing the design characteristics and optical quality of the new SV binos (currently on order).
http://www.stellarvue.com/binoculars.html
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Craig Simmons
Oberwerk 8x56, 20x90
Nikon Action IV 10x50
Barska 15x70
Galileo 20x60
Stellarvue 15x63, 20x85
Orion XT10 pre-Classic
Antares 10
Stellarvue AT1010
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BillC
on a new path
Reged: 06/04/04
Posts: 2100
Loc: Washington, USA
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Quote:
Probably not very many. I'll have to chalk this one up as an embarrassing learning experience.
Not really; you COULD have been talking about roof prism binos in which . . . the rear part of the prism cell acts as a stop.
Also, all of a sudden my CN messages are requiring me to scroll WAY over to the right. How do I fix that?
Cheers,
Bill
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William J. Cook, Chief Opticalman, USNR-Ret.
Founding Editor, Amateur Telescope Making Journal
20-year vet. of Captain's Nautical Supplies, Optics Dept. Mgr.
Optics Machanic, WG11-3306, Ft. Lewis, Tacoma,WA
Yata, Yata, Yata . . .
Edited by billcook (10/01/04 12:05 AM)
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KennyJ
Reged: 04/27/03
Posts: 10081
Loc: Lancashire UK
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Bill,
I TOO am suffering from the same problem of having to apply for planning permission for an house extension to allow for a wider PC screen , in order to be able to read a line of print without the dreaded scrolling.
This situation arose only about two days ago.
Is there anyone out there who can help with this ?
P.S -- I wonder -- is THIS what the view is like through the Orion Expanse ?
Regards -- Kenny
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Two eyes and a preference to use both
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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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12509
Loc: Cumberland, R I , USA42N71.4W
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Is it all messages or only the one's like this thread which are forced wide by the picture inserted several posts up. Chekc another thread to see if the problem is isolated or consistent across all.
I was having the same problem, since I usually view in flat mode. Go to threaded, you'll see what I mean. I think it's just the inserted picture.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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