"Permanent" Fingerprints on front element?

[S R Massey]

I have an otherwise pretty good Canonet QL17GIII, but there are three fingerprint marks on the front element that show up pretty well with a pen light. Thing is, they aren't going away with the usual methods... Eclipse fluid - no, isopropyl alcohol - no, distilled water - no, lens pen - no, microfiber cloth - no, tissue paper - no. I've gotten pretty aggressive with it.

And no, it's not on the other side of the element.

Hard for me to believe that simple skin oils could permanently mar the surface of a lens, but I suppose maybe the Canonets had fairly soft coatings?

Is there any reasonable method for removing these fingerprint marks that won't also further optically compromise the lens? I've heard of hydrogen peroxide and ammonia 1:1, is this something worth trying here?

 

[CMur12]

My understanding is that skin oils have acid(s) in them and that fingerprints can permanently mark lens coatings and photographic emulsions. I haven't had this experience with a lens, but I have seen it on color photographs.

- Murray

 

[Chriscrawfordphoto]

I have an otherwise pretty good Canonet QL17GIII, but there are three fingerprint marks on the front element that show up pretty well with a pen light. Thing is, they aren't going away with the usual methods... Eclipse fluid - no, isopropyl alcohol - no, distilled water - no, lens pen - no, microfiber cloth - no, tissue paper - no. I've gotten pretty aggressive with it.

And no, it's not on the other side of the element.

Hard for me to believe that simple skin oils could permanently mar the surface of a lens, but I suppose maybe the Canonets had fairly soft coatings?

Is there any reasonable method for removing these fingerprint marks that won't also further optically compromise the lens? I've heard of hydrogen peroxide and ammonia 1:1, is this something worth trying here?

Lots of things can take off fingerprints. Alcohol, ammonia, windex, or lens cleaner. A fingerprint is a deposit of skin oils. Chemicals can remove these deposits. The problem is that if a fingerprint is left on a lens for a long time, the oils that make up the fingerprint will permanently etch the coating and/or the glass. Once that happens, the lens is permanently damaged. Chemical cleaners cannot restore etched glass; they can only remove oil and dirt.

 

[Archiver]

Lots of things can take off fingerprints. Alcohol, ammonia, windex, or lens cleaner. A fingerprint is a deposit of skin oils. Chemicals can remove these deposits. The problem is that if a fingerprint is left on a lens for a long time, the oils that make up the fingerprint will permanently etch the coating and/or the glass. Once that happens, the lens is permanently damaged. Chemical cleaners cannot restore etched glass; they can only remove oil and dirt.

Good reason to regularly check our lenses and keep them clean and clear. Thank you for this reminder.

 

[zane0777]

Shoot a roll under various conditions and see if you can detect any image quality issues. There's a good chance you won't.

http://kurtmunger.com/dirty_lens_articleid35.html

 

[zuiko85]

Stop looking at the lens with a penlight. Problem solved.
Through many years as a bottom feeder I’ve learned not to examine lenses too closely, especially backlit. Just blow the dust off, occasionally clean an errant finger print with lens tissue and alcohol, use a proper lens hood and that is about it.
Even brand new lenses, right out of the box, if looked at closely enough, will always have some tiny, unidentifiable particle deep inside.

 

[retinax]

Stop looking at the lens with a penlight. Problem solved.
Through many years as a bottom feeder I’ve learned not to examine lenses too closely, especially backlit. Just blow the dust off, occasionally clean an errant finger print with lens tissue and alcohol, use a proper lens hood and that is about it.
Even brand new lenses, right out of the box, if looked at closely enough, will always have some tiny, unidentifiable particle deep inside.

I agree that dust or the fingerprints on the front element that inspired the thread are probably a non-issue. But haze is a serious issue and also only seen with a flashlight...

 

[Dralowid]

Suntan cream might be the culprit. It can also melt the paint and lettering off cameras. Haven't a clue what it does to your face!

 

[zuiko85]

I agree that dust or the fingerprints on the front element that inspired the thread are probably a non-issue. But haze is a serious issue and also only seen with a flashlight...

Oh yeah, haze, alright I agree with that. Picked up a Tamron Adaptall II, 2x teleconverter for cheap. Had a obvious haze on rear element, looked like an outgassing problem. Fortunately the rear element just unscrewed and whatever it was cleaned right off.

 

[Sonnar Brian]

The glass Canon used for several elements of various lenses is easily etched. If it only shows up with the flashlight, do not worry about the images taken, Resale value is less. Just use it and be happy it's not like a wax imprint- which I've seen on Canonet lenses.

 

[farlymac]

Yeah, fingerprints is a common problem with lens coatings. Looks bad, but usually is not an issue, especially if the elements are double coated (both sides). I've got lenses with separation, coating faults, dust, and fungus , but the two things that will definitely affect the overall contrast of a lens are haze and scratches. The other stuff, you might not ever notice a thing.

PF

 

[peterm1]

I do not think it is the skin oils causing the problem, but rather the skin acids that can corrode and etch the coatings. Coatings are (or at least were- not sure about modern ones) metallic in nature (e.g. magnesium fluoride) and the layers deposited are a fraction of the wavelength of light. So, they are very easy to degrade if they come in contact with the wrong chemical. Including organic ones.

 

[Sarcophilus Harrisii]

Years ago I bought a Rolleiflex from a firm of total charlatans in New York city. When it arrived it had a large fingerprint permanently imprinted onto the front glass. It covers a significant percentage of the glass. It had other faults also not described or visible in their images. I was rebuffed when I contacted them about the disparity between their description and the actual condition of the item. After parking it in disgust, only a few years ago I remedied its mechanical faults and ran a couple of rolls of black and white through it. Results were sharp enough, but lacking in contrast, and the lens exhibited flare at the slightest provocation. Despite that I produced a couple of images with the lens that made virtues out of its flaws, but it was clearly not fit for purpose. I tried water, alcohol, lens cleaner, peroxide, acetone, to remove the print, but, you can only remove external contaminants from a surface. This print has altered the coating, itself—cleaning can never remedy that. I don't know how or why my lens was permanently damaged, but damaged, it is.

I'd suggest that whether or not the damage to your Canon's lens is consequential to image quality can only be ascertained by actually trying it. If it performs well in side lit situations, or even into the light—don't worry about it. Otherwise, (if the overall condition of the camera warrants it), the only cost effective solution will be substituting a replacement from a scrappy donor camera with a good lens. The costs of polishing and re-coating the existing lens will likely be in excess of the typical replacement cost of the camera.

In the last couple of weeks I've actually just forwarded the affected glass from my Rolleiflex to a specialist skilled in fabricating and repairing optical components for industry and defence clients. They've informed me they can recondition it and have the facilities to apply a new coating. As my Rolleiflex is reasonably clean and I acquired it so many years ago for much less than current asking prices, it is economically viable to pay for the lens repair. But I also try to take the long view. Rollei twin lenses aren't being made any more. I think it's important to try and preserve as many of them as possible.

 

[Coldkennels]

Ah, this is something I'm all too familiar with.

In 2012 I spent a fair bit of time hunting for a usable Summar. Eventually I tracked one down that was completely scratch-free - but had a thumbprint right on the front. I assumed (foolishly) that it would clean off, and paid the £89 (!) the dealer was asking.

No, it would not clean off. But it didn't matter. I took some great photos with that thing. The "look" of the Summar was gorgeous, and the thumbprint had seemingly zero effect on the images.

However, over the last decade, a fair amount of crud had settled on that front element. I hadn't used it for a couple of years, so I didn't even notice until I pulled it out of storage in the summer of 2020. I don't even know what it was - it was best described as a film of sorts, and it definitely wasn't a beneficial "bloom". The photos I shot with it looked nothing like as good as they used to. However, after a very thorough cleaning, I got it back to how it was in 2012 - fingerprint and all. It still wouldn't shift.

This is it after cleaning:



I took it to France last weekend for its first proper outing in years, and all things considered, it dealt with the harsh and bright sun quite well. This was almost totally backlit:



This one was VERY strongly sidelit, with the sun well out of frame, but you can see a reflective glint at the side:



And this was the most punishing one of them all, with the sun literally just out of frame, and a huge contrast range, but the Summar still handled it alright - although you can see a hint of lens flare:



So, yeah. All in all, I wouldn't worry about it. Part of me wonders if a proper resurfacing and polishing to remove the etched fingerprint would improve things slightly, but considering the cost that would entail and the results I'm already getting, I'm not exactly losing sleep over it.