I got a DA 70/2.4 today from KEH. It was used, condition identified as "EX+." Looks to be in great shape cosmetically, and the elements are nice and clean. However, upon close inspection, I can see some oil on the blades. Just a very small amount. If I look through the rear element with a flashlight, I don't see anything with the aperture stopped down. But as I start to open it slowly, I can see traces of oil film.
I have many older lenses that have a similar very small amount of oil visible, that work fine, and I don't worry about it. But I was surprised to see this on such a new lens. Does this seem odd to you guys? Is this lens known to have any such problems?
Additionally, I'm pretty sure the lens is backfocusing, but I can't do any tripod tests to confirm because I don't have an Arca-Swiss plate for the camera yet. But hand held at shutter speeds around 1/160 or so, at roughly 2x minimum focus distance, I am getting backfocus fairly consistently. If I set the AF adjust to +10, I think it's about right, but possibly still slightly backfocused. I suspect I may have to return this lens.
I just got the camera today, and it's the only lens I have. I should be getting a couple of other lenses in the next day or two, so I can test them to be sure there isn't an issue with the camera.