Originally posted by Nayu The seller won't take returns, but there's still the eBay money back guarantee. Should I take that route? Or try to message them first?
"No returns" is sort of a standard clause for eBay sellers but in reality, it doesn't mean much because eBay will almost always side with the seller if there's a problem that was not mentioned in the listing.
Best way to approach this is to contact the seller first and POLITELY (don't be angry or aggressive) mention the problems you are having and ask them what can be done about it. If the seller is good, they should offer a full money back on item and postage, plus return postage costing you absolutely nothing except your time. If the seller's response is not satisfactory, then start a "Item not as described" dispute process with eBay, however, you may have to bear the cost of return shipping. If you had to pay import duty, then you need to contact your customs office to get a refund.
The "dirty" element is a common problem with FA 1:2.8 100mm Macro lens. Of 20~30 of these lenses I have serviced, more than half have had this issue in varying degree. Pentax must have used some paint, oil or grease that was prone to evaporation. Curiously it all happens on the same surface, a thin film of oily residue coats the surface of third element that's facing the aperture blades. Usually, the clouding caused is very light and will not have a noticeable image degradation unless you shoot back-lit scenes wide open at f/2.8. It can generally be cleaned off 100% fairly easily. However, whilst taking a lens apart to clean is not "rocket science", I would not recommend it unless you have necessary skills and patience. Even for a pro, servicing a lens always involves risks.