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Lex
Tinkerer
Username: Lex
Post Number: 2
Registered: 02-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2007 - 03:12 pm: | 
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I am looking to replace the beamsplitter in my Minolta al-s. I found some replacement beamsplitter glass but it is 1.5-.6 mm thick whereas the original is 1mm. can a rangefinder be re-calibrated to handle a thicker beamsplitter? thanks! alex |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 176
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2007 - 03:14 pm: |
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It shouldn't be a major problem... it will throw off the lateral position of the image slightly, but this is adjustable. |
Lex
Tinkerer
Username: Lex
Post Number: 3
Registered: 02-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2007 - 03:35 pm: |
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thanks, i am going to try a piece of dichroic glass. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 177
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2007 - 04:08 pm: |
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If it's of interest, Edmund Scientific does sell 1mm beamsplitter stock. Here is a link to it: http://scientificsonline.com/product.asp?pn=3043359&bhcd2=1171148855 |
Lex
Tinkerer
Username: Lex
Post Number: 5
Registered: 02-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, February 10, 2007 - 07:32 pm: |
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rick, thanks for the link.
i was able to pick up a nice piece of dichroic that is 1.5 mm. its orange and reflects blue. total cost $.15 cost and time being a factor in the decision.
as far as lateral compensation, should the plane (facing towards your eye) of the new piece be placed so it is in the same place as the original? or do you average it because the piece is thicker? can the rangefinder mirror (that moves) be adjusted to compensate? i guess i am trying to figure out which variable (part) in the system to adjust. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 178
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 11, 2007 - 01:18 pm: |
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you're going from 1.0 to 1.5mm, so orient the mirror the same way as the old one - the more the change in position, the more adjustment you have to do.
I don't have experience with that particular model, but there will be an adjustment for lateral image position. This is most commonly done at the moving mirror position, but sometimes there is a lens between the 2 mirrors that is shifted fore and aft, and sometimes it's done in the linkage between the moving mirror and the lens. If you're into it far enough to replace the beamsplitter, you should be able to see the adjustment if it's either of the first two options.
Go ahead and install the new beamsplitter first, then adjust the rangefinder to give you correct indication at infinity (check lens focus at the film plane, unless you know for sure that its infinity position is correct) |
Lex
Tinkerer
Username: Lex
Post Number: 6
Registered: 02-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 12, 2007 - 11:54 pm: |
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Rick, Looks like the dichroic glass will not work. both side are reflective so ya get a double. i found some 1mm stock at the surplus shed for $1.75 but the thing is that its 70% trans and 30%. I am not sure that is enough to work.
http://www.surplusshed.com/pages/item/l3729.html |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 180
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 13, 2007 - 07:44 pm: |
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That stuff will work. The 50/50 stock that I link to on my site gives you a brighter secondary RF image, so I like it better, but I'm sure the 70/30 will do a decent job. I think some people prefer it. I expect that when set at a 45 degree angle it reflects more, so it may come out closer to 50/50 in a rangefinder application. |
