Whats this on my lens? >>

P

panerai

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Was checking the lens over to sell when I noticed the spots on it. First thought was mold, but after checking my other one of the same model.

It appears it might just be paint wear rubbings/dust from turning the focusing and aperture rings and aperture blades?

Lenses have never been CLA'd and this one has been sitting (no hot humid rooms) as it's the slightly better of the two.

Taken with macro and at full size, so looks worse than the small actual size

Just curious what others think?

Thanks

DON

dust.jpg
 
most likely dust. Seem a little extreme though. This happened to an Olympus 55mm lens I had. I disassemble it and give it a VERY CAREFUL cleaning.
 
Thats what I thought. Don't have the tools to start removing rings. I could build the tools, but thats added work.

I'll let the buyer do it or have it done if they like.

Thanks

DON
 
AFAIK, image quality isn't affected that much. If you have a chance make a test, I guess it would make the buyer feel better about the lens.
 
The main thing for the buyer is to make sure he's aware of it before the sale so he doesn't come back shocked and appalled to find dust in his lens.
 
I've got worse junk than that inside a Zeiss Opton Sonnar, but you'd never know it from the film scans. Some buyers do question the "Will not affect image quality" disclaimer they constantly see, and usually demand it be cleaned by the seller first.

PF
 
jim0266 said:
Ease your mind on lens dust and read this:

https://www.lensrentals.com/blog/2011/08/the-apocalypse-of-lens-dust/
Click to expand...

Well, I'm having a hard time getting my head around the idea that the depth of field of a lens can include the lens elements themselves.... have to ponder that one a bit.

Basically, unless the dust is highly reflective (which, say, aluminum powder might be), the nature of its effect is to absorb, rather than scatter, light coming through the lens (unlike scratches and cleaning marks, for instance, which scatter rather than absorb light). Scattering light reduces contrast because it diverts light into what should be shadow areas of the image, but absorbing light merely stops it from reaching the film. Therefore, the net effect of dust typically is not to reduce image quality but to reduce lens speed. The amount of this effect is the ratio of the surface area obstructed by dust to the aperture area of the lens. In your photo, an f/1.5 lens might have become an f/1.500001. Still probably within spec. If the dust is not uniformly distributed across the surface and there's a huge amount of it, it could result in one area of an image being exposed more than another, but that's going to take quite a bit of dust.

Push-pull zoom lenses are particularly prone to dust, since the lens barrel acts like an air pump every time you slide it out and back; but I don't hear many complaints about resulting image quality loss in those.

Still, buyers prefer not to see it, and some can be very fussy about it. So if you're using the lens, just ignore the dust, and if you're selling it make sure the buyer is aware of it before the sale.
 
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