16-50 - a problem lens?

Hi All,
I came across this:
http://forums.dpreview.com/forums/read.asp?forum=1036&message=24922733

Now I've had my 16-50 for 6 days and have not thoroughly tested it but there have been a few occasions when depressing the shutter button halfway I do not get a focus point, which I always got with the kit lens. I initially thought this may be down to my inexperience or the lens was already focussed (?), but some threads in the PentaxTalk forum in dpreview are suggesting the lenses may be at fault. Does anyone know anything about this? My lens has a ser. no. which corresponds to the 'bad batch' ser. nos. in the link above.

PeterM

See also:
http://forums.dpreview.com/forums/read.asp?forum=1036&message=24649119

Take a large pinch of salt with most things that you read on depressingreview.com It tends to be inhabited by nit-picking fault-finders with kanikon axes to grind!

Have a bit more of a play with it. If you do think it is faulty, contact the seller. I am very reluctant to trust internet reviews.

Kim

I believe that I have a duff 16-50 as well and am currently arranging to return it.

I have two problems with mine:

1) the SDM focusing motor is sticky. Initially when half pushing the shutter release button the focus motor refuses to move and the camera seems to go through a continuous reset cycle where the in-viewer display goes blank, followed by a click and restarts. With a little help it can be unstuck. I do this by leaving the lens cap on and half pushing the shutter release button to try and make the focus swing to minimum and back to infinity. Doing this a few times slowly un-sticks the SDM focus motor and it speeds up. Manual swinging of the focus ring makes no improvement. The focusing then seems to work fine. However if the lens is not used for a while, say 12-24 hours, it becomes very sticky again and can't be relied on. From my direction it seems as if the motor has been over "greased" and it takes a while for the grease to warm up and when not used congeals again.

2) Even when the focus motor is working the auto focus system seems to be very unreliable. It does not focus in lower lighting conditions, even outside at midday on cloudy days, and often at the long end of the zoom gives up straight away even in good lighting conditions. In this respect it is far worse than my, much cheaper, Sigma 18-50mm f2.8.


When it does choose to focus it does take very good pictures but it just can't be trusted and as, by far, the most expensive lens that I own I expect it to be much better.

Glyn

It looks like mine is going back to Pentax I'm experiencing the same as GlynM's second point and some back-focusing. Further web searching has thrown up a few interesting, albeit anecdotal, user experiences, such as using the 16-50 with firmware 1.10 improves the focusing, and that one user had poor results with the K10 but great results using the lens on the istDs.

Cheers,
PeterM

I've jut tested my '90' series 16-50mm and have no such problems. It focuses well in very low light at both extremes of its zoom range.

Same story with my 50-135mm too, no problems.

Hi Peter

How much do you like/rate this lens? I'm eagerly awaiting delivery of mine from Chris (hopefully get it tomorrow plus an 18-55 for £25 I have a location shoot on Thursday with two models and an MUA, time is short to do any serious testing, any advice regarding this lens and portraits would be welcome.

BTW: that's an very impressive arsenal you are aquiring

I'm very jealous of the 135-600.

G

That's nothing - he's got nearly as many flash guns as you have...

but isn't 1.3 required for the SDM to work?

Maybe the problem is with the SDM motor. It would explain why there is less problem on the d and on earlier Firmware. It might also explain the "delay" with the 60-250.

These are the first SDM lenses and Pentax are trying to keep their compatibility. It can't be easy. I must admit, I am not normally a first adopter for this reason though I do have the 50-135 and have a 16-50 on order.

Kim

It's certainly a beast of a lens. I honestly haven't had much chance to use it other than for a few test shots but couldn't resist it. They seem about as rare as fossilised rocking house manure.

Perhaps I should start up 'Loan-a-Lens' . . .

I think the DA* 50-135 is a super lens. Build quality and image quality are superb. Even the quality of the lens hood is improved over the normal DA hoods. It's light and compact and curiously does not change in length through its zoom range, similar to the one touch zooms except the zoom barrel turns instead of slides. It's a joy to use and fits nicely into my Slingshot 200AW bag.

That was/is my understanding too. Here is a lonk to the thread:

http://forums.dpreview.com/forums/readflat.asp?forum=1036&message=25017451&a...

PeterM