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09-18-2013, 01:50 AM   #1
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SMC Pentax 50/1.2

I picked up a fungus filled version of this lens from the junk bin and I'm planning to take it apart and see if I can clean it up. Is there anything unusual to be aware of with this lens? The front and back elements look fairly clean but at least two of the internal elements have significant mold. I don't know if it will come clean or not but it didn't cost me anything so I figure it can't hurt to try!

09-18-2013, 02:43 AM   #2
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I opened and cleand a A50/1.7 twice, there is no special tricks to know, except :
- don't loose the screw of the mount

- take picture of every step of the take appart process (to have some reminder if you don't remember when you'll have to re-assemble)

- the front plate with name can be removed by turning it like a screw. Don't scratch the front element

- dig in the forum to get the proper cleaning fluid to completely and definitively remove fungus.

- Do it in a clean place to prevent any damn dust to come on the lens when you re-assemble it.
09-18-2013, 03:16 AM   #3
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and post your cleaning shots and story later when it's done
09-18-2013, 03:25 AM   #4
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Here's an instructional video for the M 50 1.4, I suppose the 50 1.2 is pretty much the same. Never opened one but here it is:


09-18-2013, 03:44 AM   #5
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My two cents - do not loos a small ball when opening aperture mechanism. And good luck.
Another option is to ask Eric how much it would cost to clean the lens. He is really good and prices for servicing are really great.
And good luck with your project. Hope you will enjoy the lens.
Best regards,
Yuriy
09-18-2013, 04:08 AM - 3 Likes   #6
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The K50/1.2 is constructed differently from K or M 50/1.4 lenses. You will not be able to unscrew the dress ring (the one with writing on it) until you remove the ring with filter thread first. To remove the ring with filter thread, you first need to unscrew the ring that sits just above where the rubber grip ends.

1.) Remove the rubber grip. Use a thin piece of wood or plastic to gently lift the rubber away from the barrel and go all the way around.
2.) Use a sheet of rubber or rubber gloves to turn the top part of the ring (the part with silver coloured ring on it). It can be difficult to remove if thread locker has been used.
3.) You should now see three screws holding the ring with filter thread. Unscrew the three screws to remove.
4.) You should now be able to access all the front elements.
5.) To access the rear group, remove the mounting flange and then unscrew the rear element assembly.

This lens is prone to element separation and clouding of the cemented pair that is located at fourth group from the front, just behind the aperture diaphragm. To access this cemented pair, you need to remove the aperture assembly, held in place by 5 (or was it 6?) screws. If you do decide to remove the assembly, you should carefully mark the orientation beforehand as it controls the size of the aperture and thus the exposure.

Good luck!
09-18-2013, 07:18 AM   #7
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Thanks everyone, and especially tom1803. The front dress ring wasn't coming loose and I was about to drill holes in it so I could apply more pressure with calipers! Glad you saved me from that mistake.
09-18-2013, 07:38 AM   #8
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QuoteOriginally posted by revdocjim Quote
I was about to drill holes in it so I could apply more pressure with calipers!
Be careful when drilling. Drill just deep enough to give you the grip you need. I drilled to deep and made the ring even harder to be removed. You might need something like liquid wrench if it is stuck. Applying too much pressure could also cause distortion and make it harder to remove.
Good luck!

09-18-2013, 08:02 AM   #9
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I got it apart and cleaned out all the fungus and put it back together in about 45 minutes. Fortunately I didn't have to disassemble the back half; just cleaned the three front elements and then the two exposed sides of the remaining elements and all the mold is gone. I'll have to go back and do it again more carefully as it seems I left a bit of haze in my wake, but at least I know it's an easy job now!

I have a bunch of M42 bodies and several Pentax medium format bodies but nothing in the K-mount. For starters I'll probably grab a mount adapter and try it out on my NEX7.
09-18-2013, 08:26 AM   #10
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QuoteOriginally posted by revdocjim Quote
I got it apart and cleaned out all the fungus and put it back together in about 45 minutes. Fortunately I didn't have to disassemble the back half; just cleaned the three front elements and then the two exposed sides of the remaining elements and all the mold is gone. I'll have to go back and do it again more carefully as it seems I left a bit of haze in my wake, but at least I know it's an easy job now!
Good for you! That haze you speak of might not be removable, unfortunately. Fungus tends to eat into the elements, so what you're seeing might just be failed coatings. But hey, I might be wrong. Whatever happens, it's worth more than you paid for it.
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