problems with this lens

I bought this lens last year (f/n 7605461) , from an authorized dealer, and from the beginning it had problems with autofocus. The right side of the frame always went out of the focus area. Since it was unclear whether it was the lens or the camera of the Pentax KP fault, the whole set had been accepted by an authorized dealer under warranty. Here, was given to me a replacement lens Pentax-DA 18-135mm F3.5-5.6, which only very briefly should be said about: vignetting and the loss of resolution at the edges of the frame is appalling. After a while, the repaired lens (DA 16-85) was returned and I tested it immediately. Again, bad news: this time the middle and the right side of the frame focus well, but the left side of the frame is blurred. And it takes up a lot of space - about thirty percent of the total frame from the left edge. The authorized dealer has accepted the lens again and the KP for repair. Today I am waiting for the result. The total cost of this nervous situation is about 1600 euros. For me this is very big money.

I do not understand why Pentax did not carry out a lens quality control at the factory? Is Pentax not concerned about its reputation?

Back and front focus are common issue with almost modern lenses not only pentax.

vytautasengineer wrote:

I bought this lens last year (f/n 7605461) , from an authorized dealer, and from the beginning it had problems with autofocus. The right side of the frame always went out of the focus area. Since it was unclear whether it was the lens or the camera of the Pentax KP fault, the whole set had been accepted by an authorized dealer under warranty. Here, was given to me a replacement lens Pentax-DA 18-135mm F3.5-5.6, which only very briefly should be said about: vignetting and the loss of resolution at the edges of the frame is appalling. After a while, the repaired lens (DA 16-85) was returned and I tested it immediately. Again, bad news: this time the middle and the right side of the frame focus well, but the left side of the frame is blurred. And it takes up a lot of space - about thirty percent of the total frame from the left edge. The authorized dealer has accepted the lens again and the KP for repair. Today I am waiting for the result. The total cost of this nervous situation is about 1600 euros. For me this is very big money.

I do not understand why Pentax did not carry out a lens quality control at the factory? Is Pentax not concerned about its reputation?

"1600 euros"?  Are you being charged to repair a defective lens?

When it does get fixed or replaced I am quite happy with my 16-85 on my KP.

Doug

Hythloday wrote:

vytautasengineer wrote:

I do not understand why Pentax did not carry out a lens quality control at the factory?

There will be a quality control at the factory, but sometimes a lens may escape the attention of the tester

Some 15 years ago I had a faulty DA16-45mm lens which I had bought new. When I posted some pictures at this forum and compared the Sigma 17-70mm to de DA16-45mm a poster made clear that one side of all the pictures taken with the DA16-45mm was slightly blurred. I went back to the dealer and they tested the lens by taking a few pictures in the normal way and taking some pictures by holding the camera upside down. The problem became quite clear and I got another copy of the DA16-45mm which was allright.

The DA16-85mm is a fine lens of excellent quality. Another fine lens is the DA17-70mm. The colour rendering of the latter lens seems to be a bit better for RAW shooters. The older Pentax lenses tend to underexpose a bit. When shooting RAW you can correct this, giving richer colours. The DA17-70mm is parfocal. When you focus at 70mm , lock focus and zoom out to the desired focal length, your pictures will always be sharp.

That last point about the 17-70 might just sway me from the 16-85 I was planning. Very interesting feature. Thanks for posting!