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Thepurush
Tinkerer
Username: Thepurush
Post Number: 46
Registered: 01-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 14, 2012 - 11:42 am: | 
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I have been using a Minolta XD-7 since 1985. This was a used camrea when I bought it. Wehn I try to focus to infinity the rear edge of the lense always fouled with focusing screen and never allowed focusing to infinity. I examined the lense, nothing to my knowledge appeared to be abnormal.I have had a SRT 102 before. But the lense appeared to hve been handled before and a few screws were even slipping.
Now that I use NEX, I still use this lense on my NEX with an adoptor. Now the lense being quite far off from the body the earlier problem doesnt surface.
Yet I am curious to know how the problem of fouling came in to being at all?
Can any one please throw some light? |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1237
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 14, 2012 - 03:33 pm: |
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Here's a wild guess, which could be way off:
If the lens has been disassembled, it may be that one of the cells was not quite screwed back in all the way at reassembly. Increased distance between the front and rear cells might cause the lens to focus closer than it should ... which the person might have then tried to compensate for by adjusting the infinity stop farther back. Fast normal lenses often sit very close to the mirror - early f/1.4 normals were 55 or 58mm because they couldn't fit a 50mm of that speed out past the mirror - so it wouldn't take a lot of rearward adjustment to get into trouble.
Now maybe somebody can come up with a REALISTIC suggestion...... |
Thepurush
Tinkerer
Username: Thepurush
Post Number: 53
Registered: 01-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 06, 2012 - 03:49 am: |
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Dear Mr Rick, yes you are right. I measured the lengthe of lense when extended. It is 47.5 mm instead of 46. And when at infinity the fouling too is aboeut same. I examined the rear element assembly.
Though the lense elments have been assembled as they should be the the whole tube holding the elments could be tightened more so as to take the whole rear assembly closer to the front. But there is a locking compound applied which I could not break but aplying pressure by way of unsrewing the tube.
I have no idea as to how to break the lock. Any suggestions please? |
Thepurush
Tinkerer
Username: Thepurush
Post Number: 74
Registered: 01-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 24, 2013 - 09:18 am: |
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I have opend the tube with rear lense assembly. To me every thing seems to be alright, hardly any scope for any thing to go wrong in assy of the elements with in tube. I tried assembling tube in and out in every posible position. I have observed that as u unscrew the tube more, the focal length seems to increase, and by the same amout i need to move the lense asembly away from body. It is close to ininity now but not quite after unscrewing several turns. Nay thing more wd make the tube too loose. Any ideas?
thePurush |
