M 50mm 1.7 Fungi???

Picked up the above in a charity shop. It would appear to be infested with, what I suspect is fungus. Any advice of whether this is a bin job or can it be sorted within its obvious value.
regards Thoramay.

Depends what you bought it for. I'm about to have a K mount lens cleaned and I've been quoted £40. 50mm smc-a 1.7 can be bought for about £30 (if you're very lucky) - £70 (if you're very reckless) on fleabay, I often see them in charity shops etc where you can pick them up for a fiver or so.

I've seen several DIY fugus treatments listed on the internet (they should be easily found via google).
eg. http://www.mypentax.com/Fungus.html

Given the minimal value of the lens I'd give one of those a go. (nothing lost and usful experience gained if not actually ther lens fixed!

Mike

Dead easy to fix, the M 50mm is probably the best lens to learn repairs on as it's very simple. You are likely to need the following:

A lens spanner (basically two metal prongs mounted on a bar which can be adjusted for different diameter lenses)

Something to unscrew the finishing ring (the bit with "SMC Pentax-M" on) - I use the rubber strip from one of those "Boa" jar openers

Cotton buds

Domestic vinegar

Air duster/rocket blower

Microfibre cloth for final polishing of glass

Start by working out where the fungus is. On the three I've worked on it was partly on the rear element of the front group and the front element of the rear group. The front element group unscrews as a single unit after you unscrew the finishing ring, so start there as you can then strip the front group down further if required. The rear element group is best dismantled from the back of the lens - look for the metal rings around the glass with notches in. If they're reluctant to turn, try a drop of lighter fuel in the threads and leave to soak for a minute or two before you try more force.

Fungus can be easily removed with a cotton bud dipped in household vinegar. After cleaning it off, allow to dry and then buff gently with the microfibre lens cloth before reassembling. The air duster may come in handy here for a quick puff to clear any dust out of the lens - you will never get it perfect but a little dust won't do any harm. In the lenses I dealt with I simply cleaned the mould off, polished the glass, and screwed the front element group back in to finish the job.

You do not need to disturb the focus mechanism, so you don't have to worry about resetting infinity focus afterwards.

Do make sure you remember how it came apart - I tend to lay parts on the table in the correct order and just as importantly the right way around.

I wouldn't bother having it professionally cleaned, these are plentiful lenses and I doubt it's worth the money. It is however a very satisfying way to spend a few minutes cleaning one up and learning a bit about lens construction at the same time. I've since dealt with mould in a K 28-50mm and M 80-200mm, which were a bit more involved due to the need to disturb the focus mechanism to get at the fungus. Both take much better photos after cleaning!

Currently keeping my eyes open for a cheap mouldy 50mm f1.4 to rehabilitate, as I seldom see them in decent condition for £50 or less.

Matt. Thanks for your time and info. tempted to have a go. Which unscrews first and which way? It cost me just £5, so no problems. I mostly felt sorry for the charity shop. I have two A versions, so I don't need it for myself. Perhaps someone more capable that me would like to have a go at cleaning it and using it for the price of the postage.

regards thoramay.

Thoramay.

If you don't feel able to do it, (it is quite easy) I'll happily take it off your hands, for a few quid.

mowog. If you are keen to play with it, PP me your adddress. If you succeed and get it functioning again, that would please me that it has been redeemed. I want nothing more than a donation to your nearest Hospice.
regards thoramay.

Sounds good to me. - PM sent.

For future reference, the finishing ring and the front element group both screw into the filter thread (which extends further into the lens barrel than you can see with the lens assembled). The finishing ring acts as a locknut to keep the front group from unscrewing itself.

I've rescued three 50s from fungus - two f2s and an f1.7. They all work perfectly well and take sharp photos - in fact I can see no difference between them and the mint examples of both I also have.

Another useful trick (learned recently while cleaning a speck from the M 80-200mm): If you have trouble with fingerprints on the inner side of the element while trying to refit it, put a blob of blutack on the outer side and use that as a handle. Polish the glass and use the blutack to drop it back into place - any marks left by this will be on the outside and can be cleaned off when the lens is reassembled.

Thanks, Matt. Presumably it is a standard thread that turns anticlockwise to unscrew. It only compounds the problem if you get this wrong.
Mowog is going to try to redeem this lens. Just want to see it used. It was part of a ME Super plus lens that they had priced at £12 until I pointed out that the mirror was stuck and the lens full of fungi. They agreed a price of £5. It would have ended in the bin otherwise.
I now have two ME Supers with mirror problems. Is there anyone wanting to redeem these for the cost of the postage, I wonder?
regards Thoramay.

I've already got three dead or nearly dead ME Supers, so not me!

The usual faults seem to be either outright jamming (which can be cleared with a squirt of lighter fluid in the mechanism) or the other favourite of the shutter failing to cock when you wind on. I should probably bite the bullet and strip one down completely to sort it out, as there's a very good guide on the web covering how to fix them.

I mostly seem to have trouble with the self timer lever retaining screw. I've managed to shear two off and strip the thread on a third, as a result of which I now leave well alone!

Yes, the front element group is a standard thread (as opposed to the reversed ones found in the fittings for most winder lever parts).

Thanks again, Matt. I have a working ME Super. My choice for film is my Z1. I do see ME's on the web in not working condition and don't see them moving, so, I guess it is drawer room or the bin.
regards Thoramay.

Weirdly I prefer using the older manual bodies for film, I just like the experience of handling them. My black ME Super makes a very handy pocket camera with the 40mm/2.8 (well, maybe not a pocket but it'll fit in a small case).