'Grease' on lens elements

[Barry Kirsten]

I like my glass to be spotless - don't we all! I decided to dismantle my 5.6/135 Symmar as there appeared to be something in the front group that shouldn't be there. In fact it was something greasy on the inner surface of the rear element which I have managed to significantly reduce, but not eliminate completely.

The thing is, that when I clean each element of group, I usually get good results when each is held against a strong light, but when the whole lot is reassembled there is a magnifying effect which makes any contamination on the rear element look worse. Maybe this effect is a function of the focal point of the group, which would be at the iris, right?, and therefore more prominent.

My question is, how important is this in practical terms? It's impossible to keep lenses perfectly clean as there is usually something present like dust specks and even faint 'cleaning marks' (which are never a problem according to those who are selling lenses ). I can't remember anyone complaining about degraded images from their dirty lenses.

My feeling is that this film is probably OK, as it is hard to see without a strong light. However it's still there, and therefore will have some effect on image quality, however small. It's also really hard to get at, being at the bottom of the metal body that holds the front elements together, and there is no way that I can see to safely remove it (I think it's a press fit). So, advice please... stop being paranoid and learn to live with it, or send it somewhere for a proper job?

Many thanks,

Barry.

[Mark Woods]

Hello Barry,

You're probably causing more harm to the lenses with your cleaning. If there is grease, then that's a problem. Panchro Lens Cleaner is the standard of the Film Industry. I personally rarely clean my lenses, but do blow them off with nitrogen. All those little "cleaning" marks add to internal refraction and lower the contrast of the lens. Could make a lens really beautiful, but you could do the same with a diffusion filter and still have a good contrasty lens.

[GPS]

As said, the effect that it could have is mostly on the contrast. And that is impossible to see or to measure without direct comparisons with a healthy lens. Even so, the atmosphere alone can change the contrast of your pictures...
And indeed, to disassemble lens to individual lens cells is more dangerous than you probably would like to know.

[Kevin Crisp]

I think that your assumption that we all want our lenses "spotless" is probably off the mark. I shoot the dust off them when I get back from a trip. Unless I put a finger on the glass by accident (and you always know the moment you do that) I don't use tissue on lenses. I'm sure some of mine haven't been touched with tissue in 5+ years. Repetitive and unnecessary cleanings in the pursuit of perfect glass can lead to damage in the long run. How many eBay lenses have "cleaning marks"? Much better if they'd been left alone, although proper cleaning would certainly have helped avoid the marks.

A ring of moderate fog as often seen in convertible Symmars and similar vintage lenses makes no difference in the negative if you are stopping down to typical landscape apertures. I don't buy lenses with damaged rims because they can't be disassembled some day if it is worst than that. I do take them apart myself carefully with the excellent SK Grimes wrench, but I have never had internal fog or haze (fungus is another story) that can't be cleaned with a breath and one tissue. I'm not sure where your grease would come from in a non-focusing lens assembly. Getting back to your original question, try acetone sparingly, heeding the dangers on the can, followed by a breath and a tissue. Don't let the acetone get in the joint of a cemented element.

[Mark Woods]

Hello Kevin,

I'd be careful about breathing on the lens. I've had lens techs tell me that that can be a source of fungus. I know when I've shot features in the south, the good ACs do not use their breath on the lens for that reason. Again, Panchro Lens Cleaner is the standard in my industry. Here's a link to Film Tools: http://www.filmtools.com/panlencleanf.html

[GPS]

And also, forget completely about acetone. Unless you want to replace the greasy marks with paint diluted in acetone marks...

[Kevin Crisp]

Well GPS, I knew there was little possibility that you and I could actually agree on anything. I got the idea from Mr. Grimes and it has worked well for me. Yes if you soak the edge of the element, as I suggested avoiding, it can dissolve black paint. Used judiciously, as on the end of a q-tip, this is not a problem.

I also use acetone as the final wipe on lens elements I am gluing, a process I think you said people should forget trying to do at home. Works very well for that as well.

Mark...I'll try some, thanks. $15 for 4 oz but I just ordered it.

[Steven Tribe]

Fungus caused by breathing on a lens is an old wives' tale. Fungus spores are everywhere in quite ordinary environments - they are very tiny. Moisture on a lens will make the spores adhere and develop into a fungal growth.

[GPS]

Well GPS, I knew there was little possibility that you and I could actually agree on anything. I got the idea from Mr. Grimes and it has worked well for me. Yes if you soak the edge of the element, as I suggested avoiding, it can dissolve black paint. Used judiciously, as on the end of a q-tip, this is not a problem.

I also use acetone as the final wipe on lens elements I am gluing, a process I think you said people should forget trying to do at home. Works very well for that as well.

Mark...I'll try some, thanks. $15 for 4 oz but I just ordered it.

Kevin, Qtips are not a judicious way of cleaning a lens. And when you try to clean the whole surface of a lens with "the end of a q-tip" you'll see why it doesn't work either. Let alone trying to do so with a q-tip wet with acetone...
Doesn't work well, whatever Mr.Grimes says about it. First it doesn't go the the lens surface extreme (and you want to clean it there too because it's there where most of the grit is, isn't it?), second the Q tip is not a proper material (damages coating with its lint) third the acetone dilutes the paint on the lens rim, why the heck would you do something like that to your lens. Never mind.

[Kevin Crisp]

Maybe I just have really soft q-tips. They are also apparently relatively lint-free since that has never been an issue. I think you could carefully glide a moist q-tip on a lens for a lifetime and not harm it. There will not be remaining lint after the final cleaning before reassembly.

As mentioned in my response, the q-tip was for getting the grease off, followed up by a conventional cleaning and reassembly. The q-tip will leave some streaks of whatever it was you dissolved, but my experience has been that those will then yield to a conventional cleaning. Acetone is only for serious cleaning problems that a conventional cleaning can't deal with. I've seen it work, just as I've seen mere amateurs learn to successfully separate and recement classic lenses at home.

You lost me on 'the lens surface extreme,' whatever that is, and I didn't think we were talking about grit which should be blown off before any cleaning.

I've been saying all along that acetone in contact with the paint on the rim of an element can dissolve it, or, as you put it, dilute it. I would not use anything with acetone on it where there is so much liquid slopping around that this might happen. That was why I said use it "judiciously."