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Miles
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 18, 2004 - 02:00 pm: | 
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Hello,
I just bought a Baby Rollei (4x4, 127 film). However, it is missing the magnifier lens for the waist level finder. If any one has this camera with said lens, could I trouble you for the following information.
1) What type of lens is it? I.e. cemented doublet, plano-convex, double convex, etc.
2) Dimensions and mounting details.
3) Focal length, as best you can guess.
Any of the above information will help me find a replacement. My guess is it is a plano convex lens with flat side up. The focal length would be less than the screen lens distance because the screen has a finite focal length itself. I am assuming that these elements form an afocal system.
Love to know items 1-3, or if I am wrong in my assumptions. |
rick oleson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 19, 2004 - 06:04 am: |
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I don't have one handy but I'm sure it's not a doublet; I think you're right about it being a flat-up plano-convex, but a double convex is also a possibility.
The focal length would be slightly MORE than the distance to the screen to keep the system afocal, otherwise your eye won't be able to focus on the screen.
Are you missing the entire frame, or just the glass?
 = |
David Ritchie
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 19, 2004 - 10:36 am: |
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The lens is flat or very, very slightly concave on the top and convex on the bottom. The lens has been ground to form 4 straight edges just enough to fit into a square metal frame which has a 23mm opening. Sorry I cannot help with focal length. |
miles
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 25, 2004 - 11:16 am: |
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Rick, David,
Thank you very much. I have the frame I just need the lens. Thanks for the description, dimensions and the point about eye releif. |
David Ritchie
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 25, 2004 - 01:01 pm: |
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Miles,
I read your last posting and my wording on size may mislead you. The opening in the frame which you look thru is 23mm. The glass is about 29mm top to bottom and side to side. The corners are ground off to give the same 29mm. Therefore you can think of the glass as a 29mm square with the corners ground to 29mm across also. You will note that this lens slides out easily, only held by a couple of clips. |
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