[Shutter-bug]

Hi all i have a Pentax-m 50mm f1.7 manual focus lens that i love to death as a cheap walk around shooter, but have just discovered some small fungus spots forming!!

i have repaired this sort of problem with another pentax-m 50mm f2 lens so disassembling this lens is no problem, I'm just wondering how others in the forum go about cleaning their fungus affected lenses - details of solutions would be helpful as i used a woolworths branded 'fungus killer' solution last time but this was about 5 years old or there abouts- still worked great though =D

Cheers everyone, cant wait for your replies so that i can start saving my old 50.

[georgweb]

Hello Shutterbug and welcome to the forum,

I have seen fungus twice with this exact same lens. It seems to be prone to develop fungus. Seen it on the first inner surface on the back and on the front lens (on the edges, spiderweb-pattern). Show us your fungus spots, maybe they are not fungus and you can leave it as is.

About the cleaning, I always follow the same procedure: Pharmacy-quality Isopropylalcohol/distilled water 70/30 is what I use for all glas and sensor cleaning. Fungus is surface-bound and will be completely wept away.

If not, you have a damaged coating and a lens total imo.
My next harder detergent is zipper fluid (high quality).
Next is a mix of dishwasher and concentrated vinegar.
Up to here I have managed to clean multicoated glass. Older lenses will take some damage already, they are very sensitive to any kind of rubbing, too.

About the fungus, storing infected lenses separately is a good idea. I put them in aluminium foil on the windowsill to bake in the sun. Clinically you would have to clean the whole lens by taking it apart completely and rinse all parts in hydrogen or whatever will remove anything from the surfaces. After drying you would have to put everything together in a dust-free environment and lube and adjust. I have done this 2 or 3 times but it is hard work and you cannot rush it. A good compromise is to get all lenses out and separate the helical (if all this is possible) and drown the rest in a soap solution and move the aperture and all other moving parts til all grease has dissolved. Then, rinse with water, dry, zipper fluid, dry (alcohol and dry for the aperture blades). Should be enough to have a dry aperture and clean housing.

Let's be honest, with the M1.7/50 you would reasonably by a new lens and cannibalise the moribund one .-) BTW did you know that by pinching off the aperture lever you are getting an instant stop-down AV-mode shooter .-)

Best, Georg

[traderdrew]

I have wondered about something that would help prevent fungus such as a dehumidifing cabinet or device. I like the weather sealed DA* lenses and cameras and this is one reason why I switched to Pentax.

[summonbaka]

Keeping your stuff in a dry box will prevent most problems of this sort. Although the best soution is to use your equipment periodically and not to store them in a place with high humidity and without air currents to cycle air around and inside the lens.

[nater]

I have small tins of desiccant in each of my camera bags. The tins have a little window and when the desiccant color changes to orange, I know it's time to take it out and bake it in the oven to 'recharge' it so it can absorb moisture again.

[aegisphan]

Just leave the lens under the sun for a couple of days with 3-4 hours each day, you would largely cure it. The best way to avoid it is to use your lens often. That's why I think owning a handful of lenses would eliminate lots of problems (though LBA would eventually set in).

[summonbaka]

Just leave the lens under the sun for a couple of days with 3-4 hours each day, you would largely cure it. .

Just remember to wrap it in aluminum foil or white paper in the outside lens barrel so it doesn't overheat and leak some oil to the aperture blades. Remember to take everything out of the focal point or you can start a fire or burn something. Other thing you can do is put it below a UV light and it will kill the fungus and if it was a s-tak 50/1.4 de-yellow it.