3

If you go on ebay or other second hand places, you'll see a fair amount of lenses that have oil on the aperture (particularly on older lenses).

I've done some reading and it looks like this oil is from the lens barrel and when heated up escapes onto the blades.

In fact, I had to return a lens as a result because the automatic aperture was just way to slow, even in manual mode.

I've also read that you can carefully remove the oil using a Q-Tip and rubbing alcohol.

For those who have done this:

How difficult is this?

What pointers do you have?

What could go wrong?

  • I don't think there is a general answer to this. There are so many different lenses with different constructions and the possible problems will differ a lot depending on the lens at hand. This is an example of a Nikon lens being cleaned, but there are countless of others just like it. – Hugo Mar 2 '15 at 21:44
  • @Hugo Would it be more helpful to specify mount or is it really unique per lens (canon 50mm 1.8 fd being very different then DeJur 135mm 2.8)? – SailorCire Mar 2 '15 at 21:48
  • 1
    It could be helpful, but there are also a lot of lenses that are made for a variety of different mounts while sharing the same basic construction. If you have a specific lens that you are about to clean, then specify it. Otherwise you might get some general tips, but in the end the lens you end up cleaning might present unique challanges to you. – Hugo Mar 2 '15 at 21:55
  • I think for right now, I'll leave it open and general. If I need help with Lens X I'll post and link this question. At this point in time, all of my lens are good, but I want some prep knowledge just in case (or in case someone else comes across this) – SailorCire Mar 3 '15 at 17:25
3

As Hugo says, the amount of effort required to get at the aperture blades varies hugely from lens to lens, with more modern lenses (i.e. autofocus) being typically somewhat more difficult than (for example) most large format lenses, which often don't even require tools.

However, to answer your question directly you can often (depending on the lens) do a quick and dodgy clean of oily aperture blades with a clean lens tissue and isopropyl alcohol (avoid q-tips; too many fibres end up on the aperture blades). To do this, fold the lens tissue into a small rectangle, tear one edge to act as a 'mop'. Put a few drops of alcohol on the torn edge, then very carefully drag it in a circular motion around the surface of the closed aperture blades. Use a similar process with a dry tissue to soak up the oily alcohol off the wet blades before it dries. The result will be slightly cleaner, albeit smeary aperture blades.

Note: This is a risky process and you can easily get oil on other surfaces in the lens, as well as dislodging aperture blades, which then require a lot more effort to reposition.

A proper clean would be done by removing the blades, washing/drying them and reassembling.

Also; the type of aperture affects the difficulty, with simple 2-blade square apertures being simple and 20+ blade complicated apertures like this one from an Apo-Ronar being quite tricky to get back together again:

enter image description here

And; oily aperture blades don't often actually cause any issues unless:

  1. There is sufficient oil to slow the action of the aperture.
  2. There is sufficient oil to migrate/evaporate onto other parts of the lens, such as the glass elements.
1

For those who have done this:

I've cleaned up oil on the aperture blades of an old 50mm nikon RF (Range Finder) lens, some blades were stuck together and the aperture was no more circular. The lens was restored to a normal condition and I took the opportunity to clean up the inner lens elements. I'll talk about this lens, other lenses may be trickier to deal with.

How difficult is this?

It is tedious, but I wouldn't rate it as very difficult. You have to be armed with patience, and be ready to disassemble and reassemble delicate parts.

What pointers do you have?

Work in a clean and as dust free environment as possible! Bathroom is usually the least dusty environment in a house. If you have an air cleaner, turn it on in advance.

Tools needed:

  • camera to take pictures of all the steps you are taking during disassembly (to ease reassembly)
  • adjustable spanner wrench to unscrew the retaining rings of the lens elements (a photo of which is shown below)
  • micro screwdrivers: usually Phillips ( #000 or other size)
  • one or two pairs of tweezers to manipulate the aperture blades / leaves
  • lens cleaning tissue to put the lens elements you'll have removed
  • a pair or two of gloves to keep finger oil from the lens element
  • small plastic container for the aperture blades

adjustable spanner for opening the lens

adjustable spanner for opening the lens (here from Thorlabs)

Depending on the lens, the diaphragm may be located closer to the front or the back of the lens. In my case it was accessible from the front of the lens.

There are some screws on the outer body of the lens toward the front, you will have to remove those so that a kind of shell can be removed.

Unscrew the front lens element with the adjustable spanner, in my lens there was another lens element (an achromatic doublet, 2 lens elements, in this case, glued together) to be removed as well. Note the orientation of the lens elements (the front and back surface curvatures are likely different).

I then could see the actual leaves of the diaphragm. Using tweezers I've removed the whole aperture, and then proceeded to cleaning each one individually with a clean lint free cloth. I didn't use any cleaning liquid so that a very thin film of oil would remain on the blades.

Some photos of the process:

The aperture diaphragm as it originally was, that is out of shape.

the aperture diaphragm out of shape

The blades and rotating ring with spigots.

out of its housing

You then proceed to the reassembly, one blade at a time.

enter image description here

Remember to take photos of each steps, especially when you reach and remove the aperture.

What could go wrong?

  • damaging a lens element when disassembling the lens
  • putting back a lens element in the wrong orientation
  • dust from the environment settling on the lens elements surface
  • losing or damaging an aperture blade
  • being unable to reassemble the whole aperture ring

Now: as mentioned in another answer, the difficulty is of another order with modern lenses. I've disassembled a damaged canon lens from a friend and many parts were glued and unaccessible.

0

Don't touch, my friend! I've spent over thirty years learning my trade and I'm still learning. Would you dismantle your 2017 Toyota Prius hybrid or (if you're lucky) your Tesla with a half-inch spanner and a prayer? Send it to the professionals. The tools alone will cost you more than the lens is worth. And if it's something with 15-18 or more blades there's about the same number of people in the world that can do this. Trust me on that. I have 35 years in diesel engine refinishing and rebuilding, marine, HGV, and associated systems engineering :)

  • 1
    Your answer seems to conflict with that of calocedrus, who explains what tools are needed and how to go about it. Since the OP seems to be asking mainly about secondhand lenses, the financial risk in attempting a DIY solution may be low, and the cost of finding a professional who can fix the problem may indeed exceed the value of the lens. So, can you expand on the logic behind your advice? – Caleb Feb 14 '18 at 14:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.