Thanks, that would be good, hope its not paper.I think it's tempered blued steel (oxide coating). Naphtha has been what I've seen popularly used to clean them.
That's one of the best answers I've seen on a forum.The blades have pins, and if the pins dislodge from any of the blades, the opening of the aperture will become irregular. There's two pins for each blade, one is stationary, the other follows along the cam slot, and this is the one that usually dislodges. One of mine has a pin missing, it's another repair I must do, besides making new shutter blades, to completely fix the shutter. Quite often, a blade with a missing pin will still open and close due to friction alone, or there may be a burr around the hole of the missing pin, and that can be enough to "catch" the cam, and act like the pin is still there. But of course it's not, but the affected blade will be a little out of alignment, causing the aperture opening to be just that little bit out of round.
It isn't round because the blades are rubber and warped and the holes are worn.
The shiny scratches the OP's len's blades have look like other metallic blades I have seen.
does anybody know what Material this is and how to clean it?
The aperture doesn't seem round because the angle of incidence of the light and the shadow projected onto the white surface the lens sits on. This makes the aperture almond-shaped, but in reality, it likely isn't. I bet the actual aperture is as round as it should be.
Yup, looks like regular metal blades like so many.
I suspect there are two components to the fouling you're seeing. One is rust, the other is probably just a tiny bit of graphite that was used by means of lubrication. The graphite as such is not really an issue and can actually help. The rust is more of a problem and may not clean off with the regular naphta approach, but disassembling the aperture on a lens like this is usually not terribly difficult.
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