Dirty Lenses - Does it matter?

dberger said:
Oh brother. . . not only is it a myth, but this spit-enzyme-harming-lens-coating myth does not even apply. Amylase, which digests starch, is the only enzyme of note in human saliva. There are other salivary enzymes, but the whole issue is moot because to clean a lens, you are supossed to breath moist air on it, not spit all over it. Moisture in the warm, moist air from the lungs condenses on the lens surface in nice teeny-tiny droplets, which you then wipe off with some form of micro-cloth. No saliva should hit the glass. Voila.

cheers,

David
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Hmmm.. theoretically, this is correct, but it's not backed by personal experience. In the contrary. A while back, when I got the first dust bunny on the sensor of my DSLR, I thought 'Hey, I'll gently blow it of. I'll even take care not to spit on it, just gently blow'. What happened was so counter intuitive, that I should have kept the test pictures after that and written a scientific article to be published in Nature..

After the moisture of my breath evaporated, there were huge numbers of very tiny spitlets (is that what they're called?) on the sensor. Basically it looked like I had airbrushed the sensor, and I had even made conscious effort to avoid that. It took much effort to get it all off the sensor again..

So, even though you take care not to spit on a lens, it's quite probable that it still ends up there, complete with enzymes, and whatever else there can be there like bacteria.

But all that will not even be as harmful as the acids, oils and fats that are present on the skin of our finger tips..
 
This is an interesting example of what one would call the layman's etiology. Enzymes are highly specific and thus synthetics won't be affected by saliva. The scientific test of course would be to vapour water (not destilled) at the sensor and see if the phenomenon occurs again, but I guess that won't be done :).
 
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pvdhaar said:
Hmmm.. theoretically, this is correct, but it's not backed by personal experience. In the contrary. A while back, when I got the first dust bunny on the sensor of my DSLR, I thought 'Hey, I'll gently blow it of. I'll even take care not to spit on it, just gently blow'. What happened was so counter intuitive, that I should have kept the test pictures after that and written a scientific article to be published in Nature..

After the moisture of my breath evaporated, there were huge numbers of very tiny spitlets (is that what they're called?) on the sensor. Basically it looked like I had airbrushed the sensor, and I had even made conscious effort to avoid that. It took much effort to get it all off the sensor again..

So, even though you take care not to spit on a lens, it's quite probable that it still ends up there, complete with enzymes, and whatever else there can be there like bacteria.

But all that will not even be as harmful as the acids, oils and fats that are present on the skin of our finger tips..
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Peter.... you exhaled on a sensor! Yikes.

Anyway the gent was discussing the front element of a lens.. way different.

Hope your sensor is okay. Take it to the local rep for your camera maker they do a job that is way better than DIY. BTW I mean a rep IE a Canon warranty centre or Nikon warranty centre.. for the corresponding camera.
 
jan normandale said:
Peter.... you exhaled on a sensor! Yikes.

Anyway the gent was discussing the front element of a lens.. way different.

Hope your sensor is okay. Take it to the local rep for your camera maker they do a job that is way better than DIY. BTW I mean a rep IE a Canon warranty centre or Nikon warranty centre.. for the corresponding camera.
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Well, you can only learn by trying or copying.. and I'm the experiment type of guy..

And yes, I got the sensor clean, so that's not problem anymore..
 
Instinctively, I always thought that dirty lenses (or scratched lenses) would cause pictures to become unsharp.

But if you think this through, it's easy to understand that dirt doesn't cause unsharpness. What happens is that light passing through the lens hits the dirt or damage and gets strayed around in random directions. The only effect of this is general flare and a darker negative. Chances are good that printing the negative on higher contrast paper will still render a very acceptable result.

If you have strong light sources in the picture or direct light on the lens, dirt can be a real problem, though.

Unsharpness can only be caused if there's a continuous layer of 'dirt' on the lens (like vaseline) that covers all or most of the surface and actually 'disforms' the lens surface.

Groeten,


Vic
 
"...isopropyl alcohol, or vodka for FSU lenses"

Ondrej, my German and Japanese lenses have loved vodka as much as my Industar loves it. Do not underestimate the holy fluid.
 
The worst is when you find an old lens where the front element is reduced to a hazy mess because of overzealous cleaning through the decades. This is hard to live with.

It's amazing to find a near pristine 40 or 50 year old lens. I like to find them at yard sales when they have filters on them, have been kept in cases, and the glass is mint. The best finds are wides or teles which the original owner almost never put on the camera or used.

But most people are far too concerned about minor flaws in glass. Or they think that a scratch on an element is going to show up as the same scratch in every photo, a common misperception.

An oldtime photographer's trick was to fill in big scratches on front or rear elements with matte black india ink.

This cured any ill effect such as flaring from the defect, and you could still take near-perfect shots with a badly scratched lens.
 
Edward Felcher said:
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An oldtime photographer's trick was to fill in big scratches on front or rear elements with matte black india ink.

This cured any ill effect such as flaring from the defect, and you could still take near-perfect shots with a badly scratched lens.
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Hi Edward, do you have a resource or URL on this idea? I'm intrigued.
 
Edward, have you ever tried this? I'm trying to figure out the actual act of application of India Ink to scratches and I'm baffled as to procedure. Lots of words about "just use India Ink" but not a clue as to process...
 
yesterday I was speaking with a dutch photojournalist and was looking at his m6 with 35 asph cron and the lens was so unbeliveably dirty I couldnt believe it but he said there was not problems so he never bothered to clean it. And this was not just ususal dirt, there was even a hair stuck in the hood mount that crossed the front element, yikes.
 
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