Oily Blades

Hi Guys

While browsing the forum the question of oily blades crops up, so I decided to have a look at my Super Tak 135mm and hey pesto "oily blades" plain to see, it seems 3 blades appear to show signs. Now my recent pics from the weekend all appear fine, sharp, coloured as normal, so how are these oily blades detrimental to the condition of the lens/pictures?

Kind regards

Oil is sticky and it stops the diaphragm closing down quickly enough when the shutter is released. The result will be over exposure.

If you operate the diaphragm manually you'll be able to see how "snappy" or otherwise its action is.

Thanks John

I must admit it meters very well and fingers crossed up till now I'm not suffering from over exposure, apart from human error of course. Next question, is it easily rectified or shall I just leave as is?

Kind regards

It's a professional job, not difficult and shouldn't be particularly expensive either.

guys,
does anybody have a picture of lens with oily blades?
I'd really like to know what to look out for!

Thanks

Peter

Oily blades aren't a problem for lenses where the movement is completely controlled by the aperture ring.
When you have a spring (A control) then it becomes a problem since the spring is never strong enough (from my experience) to return the blades to their position.
Oil could all spill into the lens elements, but I have never seen this personally.

Cheers for that Ed being the lens is manual I'll leave it as it is, I can't see any oil on the elements and my latest pics have'nt shown up any smudges, smears etc.

Does anyone know a suitable solvent for getting rid of the oil? I've an old lens with this problem and when I cleaned the aperture with isopropanol or sonicated it in acetone the oil leaked out of the grease again within a few days. I there anything I can use to get rid of the grease/oil more premanently before regreasing with a suitable grease?

My method has been to strip the lens to the point where the iris mechanism is seperated from any glass elements (but no further - I learned from early mistakes that taking the assembly apart meant trying to re-align blades and that's a horrible job), then submerge the assembly in a bowl of warm water and washing-up liquid. While the assembly is submerged I then operate the iris repeatedly (about 100 or so times) from fully open to fully closed. Remove from water and dry the assembly off with a hairdryer while continuing to open and close the iris. You'll find as it heats up the iris will stick again but don't worry - you can stop the operation at this point and when it all cools down you'll find it'll work like new.

When I put a lens back together I will thoroughly clean all parts (usually, again, with warm water and washing-up liquid) but the only lubricant I add is a silicone grease on the helicoid - nothing else in there should require lubrication and everything (bar the helicoid) should be bone dry before you put the glass elements back in.

I don't have a picture to hand but you'll see a sheen over (one or more of) the blades that will look a little like oil on water - the blade(s) will appear as if they're wet (which of course they are).

Don't forget though that some older preset lenses are supposed to have oil on the blades as they're designed to be opened and closed by hand rather than relying on a tiny spring.

It would be better if you said what make the lens was? You need to completely remove the old grease which is usually a mix of oil and soap. Because its separated hot water or as Hefty suggests with washing up liquid should work. Wipe off as much as you can at first. There are some good illustrated articles on the net, but you need to find the one with your lens.

Even some recent lenses such as 15 year old Tamrons are showing this problem.

Algi

Thanks everyone.

I'll try the hot water and washing liquid trick - I'm able to strip the lens down until all glass has been removed. I'm still a bit surprised that the isopropanol didn't clean out all the grease though.

It's an old Makinon 135mm lens.

I doubt you'd find that one on the web. There is one on stripping a CZ 135mm.

There's a good French site somewhere that shows you all the processes and explains the materials used.

Algi