Repairing/Cleaning Fungus-Ridden Pentax-M 50mm 1:1.7

*iht* · 09-08-2009, 08:10 AM

Hi there,

I just got a Pentax ME Super package from eBay with a Pentax-M 50mm f1.7.

Unfortunately the lens came with fungus (see below):

The seller was not a camera expert and was kind enough to give me a partial refund, so no problem there (the whole package ended up being AUS$23 delivered), so I'm still happy, since the body is still in very good working condition.

I'd like to have a go at cleaning this lens. Does any of you have experience or detailed instructions on how to go about it? I have never done anything of this sort, so I thought this would be a good opportunity to learn.

The only instruction I could find was the link below. It contains instructions on taking apart the M 50 1:2, which I'm assuming is similar.

Pentax 50mm repair 1

Your input would be much appreciated!

Thanks a lot in advance.

*X Man* · 09-08-2009, 11:36 AM

Originally Posted by iht

Hi there,

I just got a Pentax ME Super package from eBay with a Pentax-M 50mm f1.7.

Unfortunately the lens came with fungus (see below):

The seller was not a camera expert and was kind enough to give me a partial refund, so no problem there (the whole package ended up being AUS$23 delivered), so I'm still happy, since the body is still in very good working condition.

I'd like to have a go at cleaning this lens. Does any of you have experience or detailed instructions on how to go about it? I have never done anything of this sort, so I thought this would be a good opportunity to learn.

The only instruction I could find was the link below. It contains instructions on taking apart the M 50 1:2, which I'm assuming is similar.

Pentax 50mm repair 1

Your input would be much appreciated!

Thanks a lot in advance.

First, you need to determine where the fungus is. If it up front? Is it out back? Then open the lens fron the end that's closest to the problem.

That link is good, but I think they go too far unnecessarily. The first part is right about unscrewing the "beauty ring" to get to the three screws that hold on that front element group. If the fungus is up front and you follow the instructions to remove the front element group, you can probably clean it and put the group back. Done.

Same if you're going in from the back. I'd only go as far as necessary. You don't need to take the mount off to get the rear elements out. They just unscrew.

Regards,
Mike

F-Stop · 09-08-2009, 11:51 AM

If you attempt this, and I wouldn't suggest you do, document/take pictures of each step and what it looked like before taking something off. The second thing I would suggest, plan enough time so you can take it apart and put it back together in one sitting so that you don't forgot anything. Unlike myself I took apart my Pentax-M 50mm f/1.4 and for the life of me can't get the focus ring stops to work, just screws itself apart. I wasn't too worried because it developed a haze between 2 laminated elements, the reason I took it apart, which couldn't be corrected anyway so I bought a FA 50mm f/1.4 instead.

I wouldn't rate this as difficult, it's just that if one thing doesn't go back in place correctly the lens is a pile of glass and metal. Good Luck!

Barnster · 09-08-2009, 08:24 PM

Originally Posted by F-Stop

If you attempt this, and I wouldn't suggest you do, document/take pictures of each step and what it looked like before taking something off. The second thing I would suggest, plan enough time so you can take it apart and put it back together in one sitting so that you don't forgot anything. Unlike myself I took apart my Pentax-M 50mm f/1.4 and for the life of me can't get the focus ring stops to work, just screws itself apart. I wasn't too worried because it developed a haze between 2 laminated elements, the reason I took it apart, which couldn't be corrected anyway so I bought a FA 50mm f/1.4 instead.

I wouldn't rate this as difficult, it's just that if one thing doesn't go back in place correctly the lens is a pile of glass and metal. Good Luck!

I am amazed on how many pieces that are in the M F1.4.So I would agree,if it's your first time,document every step on how you take it apart.Good luck!

*iht* · 09-09-2009, 04:09 PM

OK, thanks for your reply. You have succeeded in scaring me! Oh well...

*X Man* · 09-09-2009, 04:17 PM

Originally Posted by iht

OK, thanks for your reply. You have succeeded in scaring me! Oh well...

Yeah, I don't know why anyone would disassemble a lens so completely. Especially, if we're just talking about a little fungus.

Just spin off the "beauty ring" remove three screws, remove front element group. Or if going through the back, just set focus so the rear lens element is sticking out the farthest and unscrew it.

I repeat, there's no reason to disassemble the lens to anywhere near the extent shown above.

That would scare me too.

Regards,
Mike

kkui · 11-05-2009, 05:03 PM

When you take off the beauty ring, there are 6 screws. If the fungus is only the front element, which 3 do you remove? The bigger three or the smaller three?

*skid2964* · 11-06-2009, 02:00 PM

I had a Pentax A 50mm 1.4 that looked worse than yours.
Eric Hendrickson fixed mine, it came back looking and working like brand new.

Link to Eric's website

VERY affordable........ I think it was like $30 or so....

*iht* · 11-06-2009, 03:52 PM

Thanks for that. I wish it were $30, but I live in Sydney, Australia, and shipping cost alone would worth more than the lens' cost. Does anyone know of an Eric-equivalent in Aust? You guys are so blessed to have Eric resurrecting your equipment every few years!!

GerryL · 11-06-2009, 04:13 PM

Originally Posted by iht

OK, thanks for your reply. You have succeeded in scaring me! Oh well...

LOL! Really looks daunting if you see all those parts..and that is just if you don't lose any of them as some might just fall out or jump out if it had a spring...toingggg!!!!

GerryL · 11-06-2009, 04:16 PM

Originally Posted by F-Stop

If you attempt this, and I wouldn't suggest you do, document/take pictures of each step and what it looked like before taking something off. The second thing I would suggest, plan enough time so you can take it apart and put it back together in one sitting so that you don't forgot anything. Unlike myself I took apart my Pentax-M 50mm f/1.4 and for the life of me can't get the focus ring stops to work, just screws itself apart. I wasn't too worried because it developed a haze between 2 laminated elements, the reason I took it apart, which couldn't be corrected anyway so I bought a FA 50mm f/1.4 instead.

I wouldn't rate this as difficult, it's just that if one thing doesn't go back in place correctly the lens is a pile of glass and metal. Good Luck!

I know what's wrong with this lens..it has a coin inside!

*Wheatfield* · 11-07-2009, 12:08 AM

For the cost of the lens, and their commonness, I'd pitch the thing and find one that is clean. Fungus can migrate from one lens to another, so if you don't get it all, it can have pretty dire consequences down the road.

Dangermouse · 11-07-2009, 06:27 AM

I recently dismantled one of these f1.7 lenses (the one my Dad bought in 1970-whenever) as there was a fair bit of dust inside and the front end wasn't properly screwed in. Here's how to remove the front element:

Unscrew the metal ring with the lens details on

Unscrew the front element

In this case I simply used a cotton bud and some lens cleaner to wipe the dust off the inner surfaces and reassembled the lens. It's not perfect but it's a lot better than it was, and the lens is now correctly assembled. They're nothing like as complicated as the f1.4 version and you don't need to fiddle with the aperture or focus controls.

What I'm not so sure about is how to kill fungus. I usually use an alcohol-based screen cleaning fluid to clean lenses, would that do the trick?

*Wheatfield* · 11-07-2009, 09:11 AM

Originally Posted by Dangermouse

What I'm not so sure about is how to kill fungus. I usually use an alcohol-based screen cleaning fluid to clean lenses, would that do the trick?

Apparently Ponds Cold Cream will do it.

Dangermouse · 11-07-2009, 10:10 AM

I would also wonder if leaving the lens somewhere warm and dry before reassembly would help? Fungus does like damp after all. I think all you can do with these lenses is clean it out and then keep an eye on them. Don't store them with your camera or other lenses (just in case) and keep one of those silica bags near them. At least the front is easy to take off, if further treatment is needed.

Should perhaps have included the information that there are no screws holding the front element group in on the Pentax-m 50mm f1.7. The subassembly is screwed into the same threads that filters attach to and in the same manner. This also goes for the finishing ring on the front.