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12-07-2018, 09:35 AM - 1 Like   #1
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Pentax-M 100mm F2.8 very soft and distorted

What is wrong with it? I focussed this on a wet window pane.



For original see flickr. It makes some very interesting highlights and bokeh balls with rainbow edges. Maybe I should keep it for that but It doesn't seem the normal behaviour of this lens.

---------- Post added 07-12-18 at 18:38 ----------

Close up of bokeh highlights:


12-07-2018, 09:43 AM   #2
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  • Make - RICOH IMAGING COMPANY, LTD.
  • X-Resolution - 200 dpi
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  • Date and Time (Modified) - 2018:12:07 17:14:47
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  • Lens ID - 1 0
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12-07-2018, 09:52 AM   #3
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It's probably a loose, missing, or reversed lens element.
12-07-2018, 09:54 AM   #4
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The back element of the lens was described as having some scratches on it, but I think the is more going on. Not typical scratches, more like stress fractures. The lens it self looks like it has hardly ever been used, so maybe the reason for that was it's flaws. The seller pointed out the scratches very well, but also said it was optically in great condition and no balsam separation. This is the photo he took of the back element:
I can't do it better myself without a flash.


Stopped down the lens gets better but the edges remain very unsharp.

12-07-2018, 10:03 AM - 1 Like   #5
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QuoteOriginally posted by D1N0 Quote
The back element of the lens was described as having some scratches on it, but I think the is more going on. Not typical scratches, more like stress fractures. The lens it self looks like it has hardly ever been used, so maybe the reason for that was it's flaws. The seller pointed out the scratches very well, but also said it was optically in great condition and no balsam separation. This is the photo he took of the back element:
I can't do it better myself without a flash.


Stopped down the lens gets better but the edges remain very unsharp.
Those scratches look like tool marks from being disassembled. Methinks whoever did the job flipped one of the elements.
12-07-2018, 10:07 AM - 1 Like   #6
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The back element seems pretty symmetrical, but the one behind it should be convex on the outside...
12-07-2018, 10:11 AM   #7
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Definitely agreeing with photoptimist here, it's most likely a reversed element.
12-07-2018, 10:24 AM - 1 Like   #8
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QuoteOriginally posted by photoptimist Quote
Those scratches look like tool marks from being disassembled. Methinks whoever did the job flipped one of the elements.
I agree. I got a very similar result to this when I incorrectly re-assembled a Kaleinar-5N 2.8/100 macro lens after servicing...

12-07-2018, 10:27 AM - 7 Likes   #9
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Maybe somebody tried to clean some fungus the box looked like it had been stored under some pretty damp conditions.

---------- Post added 07-12-18 at 19:58 ----------

Fixed it, it was the element before the rear element that was inverted. Now the lens is sharp. Thank you hive mind

This video showed me how to open it (since I figured it would be pretty similar to the 135, it was.


---------- Post added 07-12-18 at 20:12 ----------

Difference is obvious:
12-07-2018, 01:09 PM   #10
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The crazy bokeh was awesome though.
12-07-2018, 01:28 PM   #11
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Hi D1N0

You have shelves for lenses , I guess my LBA is rather non-existant all my lenses fit in one bag.

Glad you got it working again

Dave
12-07-2018, 04:50 PM   #12
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I actually need more shelves now. They have started to inhabit my desk
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