Questions regarding BF/FF and the DA* 16-50

PentaxScott · 05-01-2008, 08:09 PM

Two days ago I got my DA* 16-50 ordered from Adorama. SN 9019218. I have some questions regarding the issues with BF and FF.

I ran a wall test and a focus chart test at varying focal lengths wide open, and things seemed ok when I did them. Today I took the lens out for a run on my K10D and had very questionable results. I would appreciate any feedback/help as while I thought this lens was a keeper, Im now considering just going straight to Pentax to have this lens replaced. A few of the pictures show indication that perhaps my K10D needs service on the focusing.

http://i112.photobucket.com/albums/n..._IGP0728-1.jpg Decent focusing, Bokeh is pretty good, but the tip of the branch near the left side starts to look a bit weird as you reach the edge of the frame. f2.8.

http://i112.photobucket.com/albums/n..._IGP0729-2.jpg Focus was on the gentleman, but its obvious that he, and the dog, are soft, but the leaves behind him are sharper. 50mm f2.8

http://i112.photobucket.com/albums/n..._IGP0749-3.jpg A boring picture of the TV remote. The focus was at the 'OK/Select' button (round blue one) at 16mm f2.8, minimum focusing distance. After taking this pic, I thought for sure that the lens was bad, but...

http://i112.photobucket.com/albums/n..._IGP0750-4.jpg ...is the exact same shot (nothing moved) with the 18-55 kit lens...showing the EXACT same results.

Im not sure whats up, as the tests that I did yesterday produced accurate sharp results when using the center sensor. Is the center sensor off alignment on the body? Is the 16-50 any good?

Any help would be greatly appreciated! Thank you!

BBear · 05-01-2008, 08:30 PM

It seems like lately a bunch of pentaxians are having the same issue... I'd totally suggest you to read all the focusing threads going on because they are full of information.

And possibly one thing people are going to ask you is if you had done the AF testing. If not, google NIKON AUTO FOCUS TEST, print it out and check the results.

Later

*ryno* · 05-01-2008, 09:07 PM

Scott?
I'm at a place similar to you. I received my 16-50 yesterday, and have done some very informal testing and playing. Most chart tests were f2.8 at closest focus distance.
Last night handheld with SR on in good light, the focus point was more towards the front of the infocus area, but most of the time in focus. Today in the yard, it looked like the infocus point was behind the subject. Handheld chart tests confirmed this. Tonight I set up the tripod and with SR off, did the chart test again and got perfect results. I can't believe the camera/lens could act different, so it must be me. Did you have SR on or off for your shots? I'm looking forward to the weekend to do some more playing and testing. Keep me posted on what happens with you.
Ryan

jrforman · 05-01-2008, 09:40 PM

I just sent my 16-50 to the repair center after playing with it for the past 45 days. What I found in my lens was that it was erratic. At some times it wouldn't focus on infinity for distance shots and other times it would. Likewise it flunked the focusing test always but to different degrees. I always used a tripod, remote release, SR off. It was just different and progressed that way more over time. Not sure if this is helpful, but its what happened to me. (Could it be the Minneapolis cold?)

jrf

PentaxScott · 05-01-2008, 09:53 PM

BBear...thanks for the link. I found that link a few days before the lens arrived, downloaded the PDF file and ran a focus test best I could. I set the lens at 50 mm at minimum focusing distance at 2.8 and fired off these shots with SR off.

Focus Test 1
Focus Test 2

I also followed the advice and did a brick wall shot.

Brick Wall Test

Here, I set the focusing distance to approximately 1M and shot at 16mm at f2.8. I discovered that those posts about 'turning the SR off' for tests like these IS INDEED very important. With it on I seemed to get a HUGE amount of softness on the left side of ANY shot during the tests. All tests were done with the camera on tripod, and the shutter being tripped with a 3s mirror lock up via wireless remote.

Whats really funny is that not more than a week prior I was able to snap this AMAZINGLY sharp shot with my kit lens.

Skyelar

Im really not sure whats going on...

247nino · 05-02-2008, 12:21 AM

your test chart shots look good,

whats the problem ?

BBear · 05-02-2008, 07:44 AM

Originally Posted by 247nino

your test chart shots look good,

whats the problem ?

I was going to ask the same thing... the results look pretty sharp!

also, search fro Dresden_Phoenix or something like this... he thought he was having AF problems but apparently he realized he was doing something wrong..

I didnt really understand his explanation, but you should read it!

Later

PentaxScott · 05-02-2008, 08:47 PM

My concern was mostly over the shots I took after the test pics (see first post). It just seemed like the camera was missing focus. In all honesty, it could have just been me..

I ran another series of tests this morning. Took a series of pictures at difference distances of the nutrition label against a box of crackers (exciting huh...). Anyhow I took the pictures at different distances all at f2.8 and the shots were sharp as a tack. Im not going to post them since there isnt much to see...

Thanks for the help and advice.

*ryno* · 05-06-2008, 09:30 AM

I've done more testing and the problem I have is at minimum focus distance, I get focus behind the target. I've seen this with every lens, so It's probably a camera issue, not a lens. I've read that this problem is easily fixed by pentax service. We'll see.
Ryan