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finger smudges on front element and cleaning


stump4545

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finger smudges on front element are annoying but do they really effect image quality?

 

it is ok to use a lens cleaner spray and lens cloth to clean front and back element or will this cleaning process really remove lens coatings over time?

 

i would do this about once per month.

 

 

thanks

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I remember years ago one of the camera magazine techs (I think Norman Goldberg) was showing someone MTF testing using his baseline Summicron, and was amazed at the poor results. Looking closer he found one small fingerprint, and after cleaning the performance was back where it should be. So it can have an effect.

Use lens hoods and develop habits that avoid the problem. I don't think I find a smudge more than once or so per year - unless I loan the camera to someone else.

Frequent cleaning can damage lenses, but not as much with modern coatings. Yet I would never spray cleaner directly on a lens. Use a blower to blow off dust first, then brush, and only a lens tissue or cloth when all grit is gone.

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Upon the rare occasion of a smear on a lens, I will use a little Purosol Optical on a lintless cloth. I don't know what's in Purosol, but I paid so much for it that ... well, it causes no harm.

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finger smudges on front element are annoying but do they really effect image quality?

 

it is ok to use a lens cleaner spray and lens cloth to clean front and back element or will this cleaning process really remove lens coatings over time?

 

i would do this about once per month.

 

 

thanks

 

In my experience finger marks won't affect the image quality in a perceptible way. I even have a 90 Elmarit-M with a very clear mark (can be felt, too) in the front element which has no impact on image quality.

 

I have heard (though would like to have it confirmed) that marks on the rear element run a greater risk of impacting image quality.

 

The coatings are very resistent. I have never managed to rub off or wear down coatings on my lenses. On older lenses though one has to be careful because coating technology wasn't very good and, also, the glass used was softer and would scratch easily.

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In my experience finger marks won't affect the image quality in a perceptible way. I even have a 90 Elmarit-M with a very clear mark (can be felt, too) in the front element which has no impact on image quality.

 

I have heard (though would like to have it confirmed) that marks on the rear element run a greater risk of impacting image quality.

 

The coatings are very resistent. I have never managed to rub off or wear down coatings on my lenses. On older lenses though one has to be careful because coating technology wasn't very good and, also, the glass used was softer and would scratch easily.

 

Seeing your front element automatic vote for protective filter.

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I'm sure this will produce some extra flare.

In my experience finger marks won't affect the image quality in a perceptible way. I even have a 90 Elmarit-M with a very clear mark (can be felt, too) in the front element which has no impact on image quality.

 

I have heard (though would like to have it confirmed) that marks on the rear element run a greater risk of impacting image quality.

 

The coatings are very resistent. I have never managed to rub off or wear down coatings on my lenses. On older lenses though one has to be careful because coating technology wasn't very good and, also, the glass used was softer and would scratch easily.

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Seeing your front element automatic vote for protective filter.

 

I'm sure this will produce some extra flare.

 

I bought the lens in this condition and was initially worried that it would flare but the dealer said it wouldn't. After having used it a lot in many, many different situations I have concluded that it doesn't.

 

I can't find the article I once read but this one does the trick, too.

 

Dirty lens article

 

Please don't misunderstand me, I'm not advocating not looking after one's lenses but only suggesting that image quality often doesn't degrade due to smaller marks or amounts of dirt.

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finger smudges on front element are annoying but do they really effect image quality?

 

No they don't affect image quality, but the grease can attract fine dust which then scours the lens when you clean it. Use a good quality UV filter like a B+W MRC (which also won't affect image quality) and you can not only stop grease getting on the lens, but you can clean the filter with your tee shirt.

 

Steve

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On the front element

Sharp pits or scratches or sharply defined particles of dust have little or no effect.

Smudges, like those from a greasy finger will lower contrast.

On the rear element

Large dust particles will often give a very large faint shadow when testing for sensor dust at f16 or f22 and increasing contrast to maximum.

Many years ago Gunther Osterloh advised a mixture of 2/3 pure alcohol 1/3 distilled water on a clean very often washed cotton handkerchief for cleaning lenses after removing dust and grit particles with a blower/brush.

Requires very little/no rubbing and I have used this for over 40 years with no problems at all.

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I don't believe, how many people believe, that a smudged front element doesn't alter image quality.

 

In fact smudging the front element with greasy fingers has quite a big impact, how resistant your lens is from flare.

One single fingerprint will not matter, a few though, especially after eating a fatty burger will impact a lot.

 

Just do an experiment - don't wipe your rangefinder window on your camera for a while and just shot.

Then try a nicely lit scene with a few distinct bright lightspots in the frame and be amazed, how these light sources flare into many bright rays of light, as you move your camera around!

 

Exactly the same goes for your lens - keep your fingers off!

 

I use lens hoods on all lenses, where practical and a B&W MRC filter on the lenses, I don't use hoods - these can be wiped with a T-shirt without issues.

 

I usually only get a fingerprint on a lens, when acting very stupid or handing the camera to somebody else, who often funnily am attracted with their tiny little, greasy sausage fingers to the best hidden front elements behind the deepest of lens hoods ;-)

 

I shoot mostly with two bodies, so lens hoods or good filters are mandatory, as one of the cameras is usually dangling from a shoulder.

 

Clean your glass sensible and only if really necessary. Having a fingerprint makes cleaning it off properly necessary.

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I think this might be of interest: Dirty lens article

 

I just breathe on the front element and clean it with a microfiber cloth used to clean glasses.

 

Just as long as one is sure that the cloth designed for spectacle cleaning hasn't been impregnated with anything (I think Leica specifically caution against this). Better perhaps to use a microfibre cloth specifically intended for lenses. Otherwise I would do exactly the same thing - breathe gently and wipe. Simples!

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The fingerprint marks are slightly acidic which can result in etching of the glass/coating if left on for a long time and not removed promptly. Breath and a microfibre cloth are pretty good (my favourites), and for really stubborn marks there are numerous solvents and fluids available as well as polymer films which can be painted on and then peeled off along with all residue - its worth checking with the manufacturer or a specialist repair for advice as to what to use.

 

FWIW all contaminants on lens surfaces have the potential to affect image 'quality' but whether they do so noticeably depends on many factors. In general they increase flare (and thus lower contrast) but mostly do so to an irrelevant amount unless they are really bad. I've also seen etched fingerprints on older lenses, and these marks cannot be removed and will at best reduce the value of a lens significantly even if they don't affect performance significantly.

 

Front element chips are best filled in with black paint as they can create flare spots and veiling flare. Once they are blacked in they will no longer do so although they will reduce the effective aperture by a miniscule amount. I've had and used chipped lenses which have performed superbly once dealt with in this way.

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In fact smudging the front element with greasy fingers has quite a big impact, how resistant your lens is from flare.

One single fingerprint will not matter, a few though, especially after eating a fatty burger will impact a lot.

 

Yes, this I do, however, agree with. It reminds of that old technique for soft focus, to smear petroleum jelly on the front. Clearly such larger amounts of marks will affect quality.

 

Thanks, Paul, for the tip of filling chips with black paint. Quite logical actually. As for the impact of fingerprints (which, usually, are acidic and greasy at the same time) I am wondering about the time scale for any impact on the coating.

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It really does affect image quality. This one is a 50% crop but you can see it even at small sizes.

 

I keep a lens pen on me in my camera bag. They do a great job of removing grime. Especially those coated B+W filters which are super hard to clean.

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That one above was actually on a job. Luckily it was just the recce day. I learned the lesson though and constantly check my front element now. They are never anything but pristine now and those lens pens do, in my opinion, the best, quickest job with the least fuss. Just have to make sure you blow and brush before and after.

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