Aperture blades are free from oil!!!

[Uri A]

What is this business about oily blades ...?

Over the years I must have owned fifty lenses in every format and vintage (since the 1950's, anyway). Never seen oil on a blade. Is this a real thing, an antiquated thing that has carried over into modern parlance, or some weird internet meme that all sellers feel the need to include as a "selling point"?

Anyone here able to show me a photo of a (modern) lens with oily aperture blades?

[chrishayton]

You'r not looking hard enough. You don't tend to see it on very modern lenses but plenty of SLR lenses for 70-80s period have oily blades (zuiko,Kiron,Vivitar to name a few frequent offenders). It doesn't cause any harm to lenses without auto diaphragms unless is gets on the glass so its not a huge deal.

[sumo]

Oily blades are unfortunately pretty common amongst lenses that have not been well kept. I think there are multiple causes but they include heat melting grease and eventually making it migrate onto the shutter blades and people trying to repair a slow shutter by flooding with solvent or even adding way too much oil either in an attempt to fix a slow shutter or to perform a "repair".
I just finished cleaning an old dial set Compur mounted Tessar yesterday and it was not pretty inside. The aperture leaves were stuck together with thick oil and the shutter blades were gummy from that oil. Opening it up I could easily see how oil could get from parts that were lubricated with too much grease or oil.

[David Lobato]

I agree it seems like a mythical problem propagated by internet lore and a fake positive selling point. But in a few cases it does happen. My 1980 55mm f2.8 Micro-Nikkor lens suffers repeatedly from oil migration from the helical grease to the aperture blades. It's been serviced 4 times and it still happens despite all the promises of high performance grease from the repair guys. It's a design flaw in the lens and overexposure is the result because the blades can't close fast enough before the shutter opens. If it wasn't so sharp I'd retire it. That's my only lens with the problem, among a few dozen of all formats.

The problem is significant with SLR/DSLR's. With rangefinders and large format lenses it inconsequential unless the blades are restricted from their full motion or the aperture is asymmetrical from the blades getting gummed up. I have an old Leica lens that looks like there's oil, but the blades are simply polished from many years and cycles of use.

[Uri A]

Thanks for the explanation(s) fellows. Migration of the grease from the focussing ring would seem the most plausible explanation, i agree David.

Guess I've been lucky. Thanks all!