Oil spots inside lens

So, I bought a used lens that was advertised as being optically perfect--turns out it wasn't. On one of the elements (by the aperture blades), there are 3 small oil drops, which can readily be seen when staring through the lens. They shine in the light--definitely not dust. One is big enough to be considered a small "blob", and the other has a sizable piece of black grease/grit stuck in it.

So what do you think guys, put up with it or return it? Flowing oil would indicate exposure to extreme heat, and even if Canon does a $150+ cleaning job, there's no telling whether more will fall--once a bad unit, always a bad unit.

Anyone have experience with oil inside? I'd have to make note of the internal oil when I eventually sell it, and I'm most certainly take a hit on the resale value.

why cant you return it? i would never take it if it wasnt disclosed...

joebokeh wrote in post #11797836
why cant you return it? i would never take it if it wasnt disclosed...

I won't drag the seller into this conversation, but lets just say he's doubting my ability to tell dust from oil. I'm just particularly interested in hearing if anyone has had any actual experience dealing with oil drips inside a lens. Repair costs, likelihood of further damage, etc, etc. Bare minimum, oil spots increase flaring.

MOkoFOko wrote in post #11797892
I won't drag the seller into this conversation, but lets just say he's doubting my ability to tell dust from oil. I'm just particularly interested in hearing if anyone has had any actual experience dealing with oil drips inside a lens. Repair costs, likelihood of further damage, etc, etc. Bare minimum, oil spots increase flaring.

If the lens was advertised as perfect it really does not matter whether it is oil or dust. If I could I would return it.

About a year ago I had a mold growing in a 28-135mm lens as a result of exposure to very high humidity. Here in Sao Paulo an authorized Canon service center cleaned the lens and calibrated the focus for the equivalent of about US$100. They did a good job.

Are you sure it is oil and not mold. Mold grows and gets worse and can damage the coating and even the glass in extreme cases.

Narwhal wrote in post #11798938
About a year ago I had a mold growing in a 28-135mm lens as a result of exposure to very high humidity. Here in Sao Paulo an authorized Canon service center cleaned the lens and calibrated the focus for the equivalent of about US$100. They did a good job.

Are you sure it is oil and not mold. Mold grows and gets worse and can damage the coating and even the glass in extreme cases.

28-135mm is about 4x cheaper than the lens I got That also necessitates a higher cleaning cost I'm sure. I'm sure it's not mold--I've seen it once in another old beater lens I got to try out. I've yet to see fungus in a lens, aside from the scary pictures available online

If you got mold/fungus growing in your lens, why would you bother cleaning and keeping it? Once you've got it in there, it's likely they'll miss some during the cleaning--and it will only come back again, right?

MOkoFOko wrote in post #11799558
28-135mm is about 4x cheaper than the lens I got That also necessitates a higher cleaning cost I'm sure. I'm sure it's not mold--I've seen it once in another old beater lens I got to try out. I've yet to see fungus in a lens, aside from the scary pictures available online

If you got mold/fungus growing in your lens, why would you bother cleaning and keeping it? Once you've got it in there, it's likely they'll miss some during the cleaning--and it will only come back again, right?

I am sorry that my "old beater lens" is not worthy of comparison to your 4X more expensive lens.

You asked a question and about cleaning costs and I was simply trying help with info from my experience. Cleaning oil should be similar to cleaning mold. You have not said what kind of lens you have and I have no idea what the difference in cleaning costs for different lenses is.

I just alerted you to the mold issue because it is really bad when it happens. I see you live in Flint, Michigan. I presume that it is not too humid there, especially during the winter; but if you you travel to humid places like the US gulf coast and especially if your lens is a zoom you should take care.

As to the question as to why I would bother cleaning the lens: Well, it is is simply my evaluation of cleaning versus other alternatives. I live in Brazil. There is not big market for used lenses; either to sell or to buy. Buying/shipping a new lens from the the US is not feasible cost wise. I only have the opportunity to acquire new lenses when I travel to the US. So spending US$100 to clean and save the lens is better than having no lens at all.

I do not understand why you think that "it's likely they'll miss some during the cleaning".....what is the basis for your comment?

"--and it will only come back again, right?" Wrong! Your premise that the the cleaning is not thorough is not necessarily true.

The mold, may in fact, occur again but IMHO NOT because it was not properly cleaned. It is humid here especially along the coast or in the rain forest. After this experience I now keep my camera and lenses in sealed zip-lock bags with silica-gel when not in use.

Return it now. The oil probably came from the blades. It will only get worse and perhaps start having the blades stick.

what does oil in a lens even look like...?

Drops of oil.

DreDaze wrote in post #11801831
what does oil in a lens even look like...?

gasrocks wrote in post #11802329
Drops of oil.

^^^ what he said I've seen it once before, so I was sure of what I was seeing. The bright shine in the light was a dead giveaway. I did a google search and haven't really been able to find any actual pictures--certainly plenty for fungus though.

The blades themselves didn't look too bad (ie discoloration). I thought of posting some pictures, but when the drops are so far in, it can be difficult to get the shots to show what your eyes are seeing. Such a pain in the butt angling the lens to the light AND lining up my camera for a manual focus shot.

And yeah, I always intended to return it--I was just curious how much worse it could get, or how much the problem might cost to rectify. I'm not above taking chances on certain deal lenses if I'm reasonably sure I can get them fixed up on the cheap.