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10-02-2009, 01:11 PM   #16
Ash
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Hi Alex,
I see what you mean.
The left side's fine but right isn't sharp.
At f/8 with adequately fast Tv this shouldn't happen.
If this only happened with f/2.8 shots I'd scrutinise the way you aligned the camera against the wall (as pentaxman suggested), but with the real world photo at f/8 this becomes less likely the culprit.
Perhaps someone else should verify this as well to confirm this before sending the lens back.
You may have the vendor replace your lens or have it repaired under warranty. Either way, you'll be right - and you should (if you still want to) get a perfect copy of the 16-50 to enjoy.

10-02-2009, 03:31 PM   #17
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yeah please id like to have as many comments as possible.

And Ash here is a real world situation on this photo. f8 signs on the left are readable. Streetsings on the right side totally blurred.

http://picasaweb.google.com/alexpentax27/UntitledAlbum#

Last edited by Burgerbrater; 10-02-2009 at 04:03 PM.
10-02-2009, 06:16 PM   #18
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QuoteOriginally posted by Burgerbrater Quote
yeah please id like to have as many comments as possible.

And Ash here is a real world situation on this photo. f8 signs on the left are readable. Streetsings on the right side totally blurred.

Picasa Web Albums - alexconrady - Untitled Album
This is understandable in this case because the street signs on the right appear to be a much different distance from the lens than the street signs on the left.
10-02-2009, 07:22 PM   #19
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The lens does look a little weak on the right side. The brick wall test is the only one you can draw any conclusions from because it is very important that the test be conducted with the focal plane of the lens exactly parallel to the test target.

You can exchange the lens, but there is a good chance that you will not get one any better than the one you have. I got three 16-50s, the first one was badly decentered, the second one was mildly decentered, and the third one was badly decentered. I may have kept the second one if I had known the third one would be worse.

If you sent it to Pentax, you probably have a better chance of getting a good one back. I thought about doing this, but I had a hard time convincing myself to send a brand new lens in for repair.


QuoteOriginally posted by Burgerbrater Quote
Hi Ash,

I have tested the lens. I am dissapointed. It seems to me that not matter what f stop the right side is now decentered.

I put examples in a picasa album. Would kindly take a look and see what you think.

thanks,

Alex

Picasa Web Albums - alexconrady - Pentax 16-50m...


10-03-2009, 06:41 AM   #20
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By the way the autofocus still doesnt work up to a 100% I had problems again the lens wouldnt focus at all inside my apartment

Last edited by Burgerbrater; 10-03-2009 at 06:55 AM.
10-14-2009, 09:10 PM   #21
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Hello Everyone,

what week. Some of you (like Ash) might already know that I got the 16-50mm now too. However the first one (9027713) didnt focus at all motor was broken. Returned it. The second one (9023188) was fast and smooth however this time the bottom of the the images were completely soft. Not good. Returned it. Now I got the third lens of this kind and I would kindly ask you guys to take a look at my samples that I took and uploaded. Again the right hand side of all images seems very soft. Too soft in my opinion but I wanted to get your opinion as well. Please take a look, you would really really help me in my descision if I should return this one as well.

Thank you,

Alex

Picasa Web Albums - Alex Pentax User NY - 4rd lens test
10-14-2009, 09:34 PM   #22
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Alex, please provide the link for the photos on the post for us to click on.
Sad to hear all these issues - I just wonder whether some vendors just recycle the returned lenses for some other unsuspecting customer to buy, hoping they'll just accept it as is...
10-15-2009, 05:34 AM   #23
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Ok sorry my fault, here is the gallery please please help


Picasa Web Albums - Alex Pentax User NY - 4rd lens test


Last edited by Burgerbrater; 10-15-2009 at 08:37 AM.
10-15-2009, 08:44 AM   #24
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I even adjusted the back/front focus setting onmy k20d i dont know. It seems the opposite is now happening riight hand side ok, left corner to soft

Picasa Web Albums - Alex Pentax User NY - 4rd lens test

I am at a point where I am thinking about bying the sigma 18-50mm EX macro

Last edited by Burgerbrater; 10-15-2009 at 10:06 AM.
10-15-2009, 01:21 PM   #25
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i know its a little bit annoying but please help me and look at the samples
10-15-2009, 07:14 PM   #26
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Well mate, to me any perceived corner softness in the wall shots are in keeping with being out of focus due to a thin DoF (remember, focusing at the wall in front of you is slightly closer than the part of flat wall at the extremes of the image). If anything I thought the RIGHT side looked a little softer than the left. But there are a lot of variables when interpreting such results, and the biggest variable is often the culprit - the user. Camera orientation, leveling and wall unevenness, all contribute.

And in the real life images, there's just not much softness to speak of at f/6, as you'd expect from a good lens. It's a keeper from these images, so keep testing it yourself for more real life results.

Last edited by Ash; 10-15-2009 at 10:54 PM.
10-15-2009, 07:30 PM   #27
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QuoteOriginally posted by pentaxman Quote
I'll have to disagree with you on that one.
There are two Sigma 18-50mm f2.8 with the newer macro version being the better lens. I don't think it is clear in either post which lenses are being posting about.

Thank you
Russell
10-15-2009, 07:46 PM   #28
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Well it is not nice to say it is my fault - that I somehow cannot operate the camera. Fact is that even at f2.8 the right side is more softer than the left. That is not ok. At least not for a lens that one pays up to 800 bucks for.

I mean the sigma 18-50 that has macro.
10-15-2009, 10:53 PM   #29
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That is not what I implied.
We are all human and it's extremely difficult to do an exemplary IQ test on a lens wide open even if we think we're doing it right.

So the slightest shift of the camera from being perfectly perpendicular to the wall to 0.5 degrees off could mean the difference between evenly blurry corner fields and uneven blur from L to R. Try the same test on any other wide lens wide open and see if you get the same result...

That is why real life examples at infinity focus are much better to use for such a 'test'.
If you firmly believe your copy is bad, you may have no choice but to send it back for service/replacement/refund.
10-15-2009, 10:57 PM   #30
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Also have a look at what I meant about corner softness due to curvature here:
How To Test A Lens
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