Checking for oil on aperture

[Unicronatron]

Any advice on the best way to check for oil on the apeture blades of a used lens? This is for a dslr lens if it makes any difference.

Not sure how to go about it and what exactly I'm looking for.

I'm thinking of picking up a used lens that's in a very "well loved" condition and want to be quite thorough before purchasing since it's seen some heavy use.

Pretty confident with everything else to check apart from this.

Thanks

 

[stevelmx5]

Any advice on the best way to check for oil on the apeture blades of a used lens? This is for a dslr lens if it makes any difference.

Not sure how to go about it and what exactly I'm looking for.

I'm thinking of picking up a used lens that's in a very "well loved" condition and want to be quite thorough before purchasing since it's seen some heavy use.

Pretty confident with everything else to check apart from this.

Thanks

If there's oil on the aperture blade you will be able to see it when looking through the lens (once you stop it down). It will look wet/shiny as the blades should be completely dry. Also, if you stop the aperture down to the smallest (e.g. F22) then open it up to the widest, the blades should open without sticking or being slow.

 

[Nod]

If you can stop the lens down manually, go from the smallest aperture to half way open and back. Look down both ends and see if you can spot a line where the aperture blades reached.