Fungus

hope you don't mind another member from across the pond.
i've been lurking here for a while and i've been impressed with many aspects of this site. i was really impressed with the threads about taking lenses apart and fixing them. that's the reason for this post. i recently got a A70-210 f4 from ebay. from a UK seller. i only paid 15USD for the lense. the lens was rated OPTICALLY PERFECT but would not focus. i figured the grease had hardened and i was right. lens focuses perfectly now. the problem is there is a small amount of fungus on the objective lens. it appears to be very new. i'd like some instuction on how to access this lens and remove and clean the fungus.. hopefully this does not require the complete lens to be dismantled..

TIA,
roy

I don't have any experience taking that particular lens apart but I have taken my Vivitar Series one lens apart and its quite easy. It does help if you have the right tools, lens spanners etc. (all available from www.micro-tools.com )

You might do well to start by having a look at www.mypentax.com where you will find a step by step guide to dismantling a standard lens (Zooms are more complicated) and some useful info on lens related fungal infections.

I used acetone to clean mine. Worked great.

If, like my Vivitar, your front element is just one piece of glass, you should be quite succesful in just removing that and cleaning it. If however it is a lens group made up of 2 or more lenses, and the fungus is between them, bin the lens as it is not economically viable to clean it. In this case the individual lenses making up the group have to be separated, and that is a professional (read expensive) job.

If you undertake this exercise, do make sure you are in as dust free environment as possible.

thanks peter for the links. i was hoping someone would come along that has experience with this particular lens. i've taken the front lens off of another 3rd party zoom and it was very easy. roll back the grip and remove 4 screws and the front barrel w/lens came off..

roy

I do have the same lens, but not with me. I've just had a look at http://kmp.bdimitrov.de/lenses/zooms/long/A70-210f4.html and it doesn't look to me as if the front element has the bezel, found on most primes, which you unscrew with a rubber cup tool.

I'm not a lens repair expert so do wait for others more knowledgeable than I to offer their advice.

Whilst I have taken lenses apart, cleaned them, and put them back together again, they are examples that would otherwise go in the bin (some of my less noteworthy ebay purchases). Except for my Vivitar Series One 70-210 Macro, that was particularly dirty inside, not fungus, just gunk, and it cleaned up well.

From experience, having hunted around my bedroom carpet on my hands and knees for a tiny spring for what seemed like days, work in a clean & light environment. Preferebly on a white surface, and nowhere near long pile carpets. Drop a tiny screw and it'll get swallowed by the carpet.

Also, try not to remove the aperture ring if you can avoid it. There is a tiny (and I mean very tiny) ball bearing in there with an even smaller spring behind it. If you do have to remove it, this is where the white working surface comes in handy.

I'm sorry I can't help much more until I'm reunited with my lenses on Thursday.

well the question is rather moot now as the seller finally responded and is going to credit me as soon as he gets the lens back. including all shipping charges. he's in the UK also..
this lens did have 2 small holes drilled in it at the filter ring. evidently someone else wanted in also. anyway, i did fix the focus problem for him..

i also set this lens on it's objective on some aluminum foil in the midday sun for a couple of hours and the fungus is VERY hard to even see anymore..

roy