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11-18-2009, 04:15 PM   #1
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Restoring an old friend: 50mm f2

Hello,

I've had this lens for a few years but didn't use it much because it had dust and some fungus inside. I have some experience disasembling cheaper lenses so last week I decided to give it a try to this one. After all, this is most likely the most common 50mm lens in Pentax history.

Before: fungus (or mold) was behind the aperture blades and the most dust behind the front element.




During surgery.


The end result:




Test with the K100DS. Absolutely no PP. Straight from the camera.
1/800 @ f8.0


Click here for the full size pic:http://images52.fotki.com/v644/fileIjuu/9cd8e/4/1233394/8163544/IMGP0757.jpg

I feel like getting a new lens for free

What do you think?

Thanks,

11-18-2009, 05:02 PM   #2
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Well done!
The M/A50 f/2 isn't as highly regarded as their f/1.4 and f/1.7 brothers, but not bad lens at all, especially considering the price. I learned much from the M version of the lens, possibly the cheapest way of exploring low-light-photography without a flash.
11-18-2009, 06:44 PM   #3
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Very cool. Problem fixed and you did not have to go deep into the innards! Good job!

Steve
11-18-2009, 08:35 PM   #4
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I just got a 200mm Cosina prime with fungi. Seller refunded my money so I feel I can experiment with a cleaning. Any experience with teles or other general advice would be much appreciated. Also, did you just use "standard" lens cleaner or something else?

Thanks.

11-19-2009, 04:45 AM   #5
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I've got to do this - when I find the time - to a M50 f2 that I got as part of a package. It has lived a very hard life. Aside from major cosmetic damage, someone even bent the aperture lever. Thanks for the photos and inspiration. Restoration is very satisfying. By the way, jheu02, I used cold cream as a fungus remover on a Canonet G-III 17 with excellent results. (It's also a softer, more touchable camera now. )
11-19-2009, 05:46 AM   #6
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I've also heard about using vinegar as a fungus remover - has anyone tried this and does it harm lens coatings?
11-19-2009, 06:51 AM   #7
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Good work, the f2 is a hugely under rated lens.
11-19-2009, 10:57 AM   #8
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Thanks for the comments.
I have used the standard lens cleaning solution with good results. I've heard about the Pond's cold cream as Mike mention but never tried it myself.
As for advice, make sure you have plenty of time and space to do it. I use a white piece of cloth and lay the parts in order as I take them out and in the correct orientation so the reverse process can be easier.

Thanks,

11-19-2009, 11:12 AM   #9
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I was doing more searching on the net last night and read about the Pond's, Vinegar and also hydrogen peroxide for fungus removal. I did have a question about getting at the rear element. I thought one of the threads stated that I wouldn't need to take the whole mount assembly apart to get at the element, thus avoiding possible problems with the aperture blades.

Which of the 8 screws on the back do I unscrew: the 4 smallest on the black part of the mount, or the 4 larger ones that are on the chrome ring?

I can post either a photo of the lens in question, or if there's a web site (I missed during my searching) which shows the steps in progress, that would be great. Even though I tinker with a lot of things, I don't want to do unnecessary work which could foul things up. I've only got zooms in the longer range and was looking forward to this as it's a prime.

Thanks again.
11-19-2009, 11:17 AM   #10
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Do you have a picture of the lens? I suppose the 4 larger ones are for the mount. Usually, to remove the rear element you only remove retaining rings, not screws. But I can't be sure on this case. Post pictures so we can all participate in this virtual surgery

Thanks,
11-19-2009, 12:18 PM   #11
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Assuming it's similar to the M 50mm f2, the chrome screws just hold the mount on. Removing this would allow you to service the aperture ring, which may be a bit notchy on a lens that's seen heavy use. Just make sure you don't lose the tiny ball bearing that provides the "click" or the spring underneath it!
11-19-2009, 12:30 PM   #12
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QuoteOriginally posted by ismaelg Quote
During surgery.
Are there step-by-step instructions somewhere that will help us take apart a lens like this?
11-19-2009, 08:07 PM   #13
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QuoteOriginally posted by ismaelg Quote
Do you have a picture of the lens? I suppose the 4 larger ones are for the mount. Usually, to remove the rear element you only remove retaining rings, not screws. But I can't be sure on this case. Post pictures so we can all participate in this virtual surgery

Thanks,

Will post some tomorrow but a funny thing happened earlier today. I started trying to carefully remove the front retaining ring, but there's no notches, so I was trying to use a rubber jar lid opener for a better grip. While trying to turn the ring, the barrel started to unscrew in the middle. So I figured, why not. I opened the lens up this way, and though I wasn't able to get the elements out of the barrel, I did do a quick and dirty cleaning through the aperture opening for the rear element and to the back of the fron element where the main spot was. I used hydrogen peroxide and then followed up with standard lens cleaner.

I was able to get most of it this was, but will still want to do a better job by getting the glass fully out of the barrel to get the edges better. But I feel a little better about having minimized what damage could be done by the fungus, as well as me mucking about in a precision instrument.
11-24-2009, 09:14 AM   #14
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Cosina 200mm f/4 - fungus

QuoteOriginally posted by ismaelg Quote
Do you have a picture of the lens? I suppose the 4 larger ones are for the mount. Usually, to remove the rear element you only remove retaining rings, not screws. But I can't be sure on this case. Post pictures so we can all participate in this virtual surgery

Thanks,
Finally got around to taking some pics. As stated before, I was able to do a quick cleaning since the lens barrell unscrewed as I was trying to unscrew a front retaining ring.

As you can see in the front pic, there's no slots like in the rear photo. Could it be that it doesn't unscrew from the front?

Anyway, when I get to working on this, especially the rear element, which rings will I need to unscrew to get at the rear element?

Will I need to do anything with the mount screws, or is that only if I needed to work on the aperture blades?

Thanks for the advice,

Last edited by jheu02; 10-13-2010 at 06:47 PM.
11-26-2009, 05:53 AM   #15
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Hi,

The larger screws will remove the mount. You don't need to remove the smaller ones as it should all come out as 1 piece. Be careful when removing the mount as some lenes have a little ball on a spring to click the aperture ring and it can fly into the 9th dimension. Form the pic I think the smallest retaining ring will allow you to remove the first element. After that the second ring could help remove the inner barrel but can't be sure.
If the lens barrel unscrews maybe you can access the element from inside, but usually the front ring (white letters information) should unscrew using a rubber grip or something.

Thanks,
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