[Stagnant]

I did some posts in this thread https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/254948-verd...-f2-8-a-2.html but for the sake of convenience I will quote them here as well.

I had quite a lot of problems with this lens. The first copy died in 2007, some months after the purchase. It was replaced with a new one, thus the adventure began. Since then It had been sent to repair shop 3 times, until I finally contacted Ricoh / Pentax imaging Europe directly. Here is a list of faults, that I experienced.
1) AF problems and wobbling front element.
2) The zoom ring did not work smoothly (required force to zoom past 28 mm).
3) The focus ring got stuck in the region between infinity and two meters. The zoom ring behaved the same way as before the second repair. Sharpness was inconsistent in the range from 34 to 36 mm.

On receiving it back for the third time, I refused to sign any papers and insisted on having the lens sent back for inspection, because the following defects had not been fixed :
* The zoom ring remained stiff from 28 mm onwards.
* To focus ring, although not being stuck any more, produced rumbling noise and around 0.35 m it produced a clicking noise and required some effort to move.
* The lens hood, due to extreme wear does not fix itself on the front element of the lens and remains loose.

This time the lens was sent to Ricoh Imaging Europe S.A. . It makes me wonder where they (local dealer) sent for the preceding repairs. Actually e-mailed Ricoh Imaging Europe, right after the lens was sent for repairs. Ricoh representative contacted the local dealer and informed me that the maintenance was performed free of charge. After refusing to sign the maintenance act and having the lens sent for inspection to Ricoh, I contacted the same representative and explained the situation. The representative told me, that he would get in touch with the dealer and sort the things out himself. After a while he informed me, that he received the lens and asked me for some shots with it. Fortunately I had some test shots that highlighted some of the defects. Shortly after I was offered a free replacement lens. Ricoh representative said, that he would examine the new lens before sending it to me, to make sure that it is a good copy. As of today, the lens is on its way to my hometown.

I received a brand new DA* 16-50. It has a Pentax a Ricoh company written on the bottom. I did not have time to develop any images taken with it, but my first impression, is that it is much sharper than my previous copy. I still don't like the behaviour of the zoom ring. It zooms easily up to 26 mm and then gets "stuck", you push it further and it works smoothly from 28 mm onwards, yet it seems tighter in that range. Spinning the ring towards 16 mm is much easier and feels completely smooth. I just wonder what is going in the quality control department.

Unfortunately my adventures did not end with the arrival of a brand new copy. The very first tests revealed that it was frequently misfocusing at 50 mm. I was unable to figure out the exact pattern of this failure and besides focusing issues were different all the time (front focusing, back focusing, focusing past infinity). Quality of the properly focused images at any focal length was outstanding. I took the lens to the local dealer and they sent it back to Pentax/Ricoh Europe service. I received the lens almost a month later. It worked fine for a couple of days and then for some reason the sharpness on the right side of the frame decreased considerably. The effect seemed to vary depending on the aperture value and the focal length but was always present.

I am starting to loose hope of ever getting my hands on a trouble free DA* 16-50. I wonder, if it is so hard to make a solid performing and predictable zoom lens for that price (roughly 880 euros) ? At this point it looks like Pentax/Ricoh offer one of the best APS-C cameras on the market, yet cannot provide users with quality optics, without "compromises", manufacturing defects etc.

[alexcox]

You have been very unfortunate with this lens. I have a reconditioned 16-50mm which is free of problems. Even though it's frustrating, you should get in touch with Pentax/Ricoh again, and encourage them to get you a good one.

[Stagnant]

The other lenses I have : FA 50 F1.4, DA Lim 21 and 35, DAL 18-55 WR and DA* 60-250 are all perfectly functional. Well I had to send DA* 60-250 for repair as well, after it received some shaking in my back pack and started producing blurry images (on a side note FA 50 was in the same bag and still works properly).