Originally posted by jeryst I plan on hitting a few flea markets this summer, in hopes of finding a few lenses. I've seen descriptions on ebay like "no fungus", "no oil" etc.
Since I've never seen these things, I was wondering if anyone had pictures of lenses with these (or any other conditions) to watch out for.
I really should take a photo of fungus. I haven't seen many that represent fungus very well. Here are two from one recent eBay purchase. (It's extremely rare that fungus is visible in eBay photos at all. The description said "may need cleaning".) Look at the front element, next to the serial number, for gray spidery lines. Sometimes fungus is in denser splotches.
Oil on the aperture blades. Aperture blades are nearly always a uniform color. Oil shows as darker blotches, usually on the edges, sometimes only visible at mid-apertures. It's easy to see oil here because the lens is apart. An LED flashlight is handy for lens inspection in the field. Other causes of discoloration are wear and rust, seen very infrequently.
Here's element separation on a Pentax-M 40mm f2.8. Coating issues also resemble this rainbow look. A few lenses are known for element separation, such as the Pentax-FA 28-70/4 zoom and some Sigma 400mm f5.6 primes.
Scratches on the rear element can really affect image quality. You'll probably notice it quickly if it's this bad
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