I got an Olympus 12-50mm with my E-M5. While I loved the concept of splashproof with a useful range at either end and a basic macro, the reality was I found the image quality to be so below what I became used to with the primes (PL14 & PL20 at that stage) that I stopped using it. In particular, anything over 35mm on my 12-50mm was so soft I wouldn't bother using it for any photos I really cared about. It didn't matter much if I stopped it down or not. The wide end was quite passable though, so sometimes it was useful as a 12mm wide lens. I had read much about sample variation - some people think the 12-50mm is an under-rated gem, others a worthless zoom lens - I was definitely in the latter at this stage. Then, a cheap second-hand 12-50mm came up. I decided to take the risk and bought it. Surely those who thought it was a great value lens weren't completely misguided? The "new" 12-50mm arrived so tonight I did some comparisons, and the difference was immediately obvious. Sharpness is significantly better most noticeable at 50mm, but also at the wide angle. The colour rendering is slightly different as well - less yellow. The one I bought has an *earlier* serial number of the same series. It is also made in China. There are no visual differences. Except, one copy is sharp as a tack at 50mm and has great resolving (still below a PL20 but very good), and the other is the worst lens I have, below even the cruddy Panasonic 14-42mm kit lens (not the nicer 14-45mm one - although funnily enough I have one of those, and it's been in the "to sell" pile for awhile, always so unimpressed with the "look" of it's photos). So if you have a 12-50mm and it's soft - sell it cheap (be honest about it!) and try buy another one. You might be surprised! Old soft 12-50 serial number = ABP307xxx. New sharp 12-50 = ABP206xxx.