16-50 De-Centered?


bychan

Link Posted 25/08/2019 - 16:06
I recently had my 16-85 repaired by Pentax (right side blurry on images, original thread here link).

It seemed okay when I got it back, but I decided to cut my losses with it and trade it back to SRS.

My initial thought was to go back to Sigma, having previously owned an 18-50 for a number of years, and never had any issues with it.

SRS didn`t have any Sigma 17-50`s, and I came across an open box DA*16-50 at a good price with 2 year warranty. I was well aware of the numerous SDM issues, but a 2 year warranty was a safety net.

However my first outing with the lens was not very pleasing, in that some images exhibit the same issues as the 16-85 did; further research suggests that the lens might be de-centered, and that this is also a known issue with the DA*16-50.

Image 1 shows a full image shot @16mm f10, tripod mounted.
Image 2 is a crop of the right side of the image, which clearly shows blurriness.
Likewise image 3 shows the full image with image 4 a crop of its right side.

1



2



3



4



What next?
Can it be repaired?
Or request a refund and purchase a brand new 16-85?
Or follow my initial instinct and go for a Sigma?

My 55-300 PLM is a pleasure to use, why is Pentax`s QC so hit and miss?

Regards
Adrian
K5IIs, Sigma 10-20, Pentax DA 16-85, Pentax DA 55-300, Pentax 70 Ltd, Metz 44 AF-2.
Flickr: http://www.flickr.com/photos/ambott/

cbrog

Link Posted 25/08/2019 - 16:26
I am very surprised at the poor overall definition of your photo obtained from your 16-50 All of the Star lenses that I have produce very very sharp images. The auto focus on my 16-50 (and the 50-135) can be VERY slow to wake up though. With mine I always watch the lens focus and make sure the focus indicator confirms. I would be very surprised if SRS sent out a faulty lens....


Roger

johnriley

Link Posted 25/08/2019 - 16:47
I feel the problem here is that the image is being assessed is the wrong sort of image for that purpose. Even at f/10, only one plane of focus is the sharpest and althjough we should have plenty of depth of field, it depends on where we have focused and how far the various components in the image are from the camera. So many variables and we can't judge it, never having been stood in that spot.

I would suggest get a broadsheet newspaper, pin it up on a flat surface and take an image at each aperture. Make sure the camera is central to the subject, that the newspaper fills the screen and that the camera back is absolutely parallel to it. The camera must be on a firm tripod for this. Then you can judge where the sharpness lies by examining the fine print.
Best regards, John

PeterKR

Link Posted 25/08/2019 - 22:19
Like cbrog I'm a bit surprised by those images.

I notice they were taken at Llyn Cwmystradllyn - I was there recently with my K50 and DA18-135 so here, for comaprison, is a shot I took, at 24mm, the other side of that fence :-
Peter


JAK

Link Posted 26/08/2019 - 00:43
I believe the 16-50 performs better at wider apertures, f/4 & f/5.6. By f/10 diffraction is starting to take the edge off its ultimate sharpness.
https://www.ephotozine.com/article/pentax-da--16-50mm-f-2-8ed-al--if--sdm-lens-r...
Also of note is that the two images were shot at 1/20th & 1/25th sec respectively so every likelihood of suffering camera shake causing unsharpness too.
A wider aperture and a faster shutter speed might have been preferable.
John K
Last Edited by JAK on 26/08/2019 - 00:55

Jonathan-Mac

Link Posted 26/08/2019 - 10:13
The 16-50mm is indeed known for poor quality control as well as the SDM problem. It's not a lens with a good reputation and if I were you I'd take it back.
Pentax hybrid user - Digital K3 & K200D, film 645 and 35mm SLR and Pentax (&other) lenses adapted to Fuji X digital
Fan of DA limited and old manual lenses

bychan

Link Posted 26/08/2019 - 15:39
cbrog wrote:
I am very surprised at the poor overall definition of your photo obtained from your 16-50 All of the Star lenses that I have produce very very sharp images. The auto focus on my 16-50 (and the 50-135) can be VERY slow to wake up though. With mine I always watch the lens focus and make sure the focus indicator confirms. I would be very surprised if SRS sent out a faulty lens....


Roger

My first purchase of a Star lens, and none too impressed to say the very least. I don`t intend to keep it.

johnriley wrote:
I feel the problem here is that the image is being assessed is the wrong sort of image for that purpose. Even at f/10, only one plane of focus is the sharpest and althjough we should have plenty of depth of field, it depends on where we have focused and how far the various components in the image are from the camera. So many variables and we can't judge it, never having been stood in that spot.

I would suggest get a broadsheet newspaper, pin it up on a flat surface and take an image at each aperture. Make sure the camera is central to the subject, that the newspaper fills the screen and that the camera back is absolutely parallel to it. The camera must be on a firm tripod for this. Then you can judge where the sharpness lies by examining the fine print.

This was taken some years ago, same location, but with a K5 and Sigma 10-20; no issues here (and also handheld).



PeterKR wrote:
Like cbrog I'm a bit surprised by those images.

I notice they were taken at Llyn Cwmystradllyn - I was there recently with my K50 and DA18-135 so here, for comaprison, is a shot I took, at 24mm, the other side of that fence :-
Peter



Lovely image, much better than I managed with the 16-50

JAK wrote:
I believe the 16-50 performs better at wider apertures, f/4 & f/5.6. By f/10 diffraction is starting to take the edge off its ultimate sharpness.
https://www.ephotozine.com/article/pentax-da--16-50mm-f-2-8ed-al--if--sdm-lens-r...
Also of note is that the two images were shot at 1/20th & 1/25th sec respectively so every likelihood of suffering camera shake causing unsharpness too.
A wider aperture and a faster shutter speed might have been preferable.

The images were taken on a tripod, so camera shake was not an issue.

If diffraction is evident at f10, then I would deem the lens not fit for purpose, in that its primary role for me would be landscapes.

Jonathan-Mac wrote:
The 16-50mm is indeed known for poor quality control as well as the SDM problem. It's not a lens with a good reputation and if I were you I'd take it back.

A refund has now been requested from SRS, and a new 16-85 ordered (good offer which ends today).
Hopefully Pentax / Ricoh have sorted the QC issues with the 16-85, seeing as it`s nearly 5 years since I bought my first copy.

Thanks all
Adrian
K5IIs, Sigma 10-20, Pentax DA 16-85, Pentax DA 55-300, Pentax 70 Ltd, Metz 44 AF-2.
Flickr: http://www.flickr.com/photos/ambott/

PeterKR

Link Posted 26/08/2019 - 15:43
Jonathan-Mac (above) said.......and if I were you I'd take it back.

My feelings also.
If you don't already have one I'd get an 18-135 instead. It may not be as fast or quite as wide but it has a longer zoom which I've found very useful and also good for pseudo macros. I got mine as the kit lens with my K50 and have used it extensively. It had bad reviews when first released but mine has never let me down and whilst perhaps not quite as sharp as the 17-50 Sigma and similar Pentax lenses I've found my copy quite sharp.

Good luck
Peter

JAK

Link Posted 26/08/2019 - 19:10
Quote:
he images were taken on a tripod, so camera shake was not an issue.

Using tripod doesn't always eliminate camera shake as the tripod can vibrate too in some circumstances, eg if its windy or even induced by the shutter movement. Also some tripods are better than others.
Was shake reduction turned off?
Did you try JR's newspaper test suggestion?
OTH maybe you found out why it was an open box item,
John K
Last Edited by JAK on 26/08/2019 - 19:39

JAK

Link Posted 26/08/2019 - 19:31
Quote:
If you don't already have one I'd get an 18-135 instead. It may not be as fast or quite as wide but it has a longer zoom which I've found very useful

Bear in mind one can crop a photo taken with the 16-85 but one can't achieve a 16mm FOV with an 18mm lens. Those extra 2mm can be really useful.
The 16-85 also pairs well with the 55-300 whereas with the 18-135 quite a bit of that range is being duplicated. Get both!
John K
Last Edited by JAK on 26/08/2019 - 19:47

pschlute

Link Posted 26/08/2019 - 21:37
The DA* 16-50 did always get mixed reviews. Mine had the slow wake-up autofocus, but optically was superb.

The OP's images are taken at slow shutter speed so movement of vegetation could be expected. John's suggestion or a brick wall test might prove it one way or another.
Peter



My Flickr page

bychan

Link Posted 26/08/2019 - 23:12
I have never considered a 18=135 due to the 2mm losss as well as the overlap with the 55-300.

JAK wrote:
Quote:
he images were taken on a tripod, so camera shake was not an issue.

Using tripod doesn't always eliminate camera shake as the tripod can vibrate too in some circumstances, eg if its windy or even induced by the shutter movement. Also some tripods are better than others.
Was shake reduction turned off?
Did you try JR's newspaper test suggestion?
OTH maybe you found out why it was an open box item,

Shake reduction off automatically via the 2 second self timer.
I would suspect that camera shake would affect the entire image, and not just parts of.

No further tests have been carried out, and a refund has been requested.

Regards
Adrian
K5IIs, Sigma 10-20, Pentax DA 16-85, Pentax DA 55-300, Pentax 70 Ltd, Metz 44 AF-2.
Flickr: http://www.flickr.com/photos/ambott/

JAK

Link Posted 27/08/2019 - 10:40
Quote:
I would suspect that camera shake would affect the entire image, and not just parts of.

That could be down to subject movement then given the relatively slow exposure. 1/20th sec wouldn't freeze that. Wind induced ripples on the water do not cover the entire area either.
John K
Last Edited by JAK on 27/08/2019 - 10:40

JAK

Link Posted 27/08/2019 - 13:13
Quote:
If diffraction is evident at f10, then I would deem the lens not fit for purpose,

This is APSC we're talking about, right? not full frame?
The smaller the format the sooner diffraction sets in.
The EPZ review has this MTF test chart:


https://www.ephotozine.com/article/pentax-da--16-50mm-f-2-8ed-al--if--sdm-lens-r...
The difference between f/8 and f/11 is perhaps higher than you may expect and at f/11 centre resolution is worse than at f/2.8.
I believe the 16-50 was designed to be more efficient at wider apertures to enable good resolution at wider apertures for sports type photography. All lenses have compromises.
Maybe you're right the 16-50 isn't fit for your purpose, The 16-85 will probably suit better.


https://www.ephotozine.com/article/hd-pentax-da-16-85mm-f3-5-5-6-ed-dc-wr-review...
The 16-85 resolution holds up better up to f/11.
Also consider that the 16-85 is a much more recent design, which no doubt helps.
John K

bychan

Link Posted 28/08/2019 - 00:06
JAK wrote:
Quote:
If diffraction is evident at f10, then I would deem the lens not fit for purpose,

This is APSC we're talking about, right? not full frame?
The smaller the format the sooner diffraction sets in.
The EPZ review has this MTF test chart:


https://www.ephotozine.com/article/pentax-da--16-50mm-f-2-8ed-al--if--sdm-lens-r...
The difference between f/8 and f/11 is perhaps higher than you may expect and at f/11 centre resolution is worse than at f/2.8.
I believe the 16-50 was designed to be more efficient at wider apertures to enable good resolution at wider apertures for sports type photography. All lenses have compromises.
Maybe you're right the 16-50 isn't fit for your purpose, The 16-85 will probably suit better.


https://www.ephotozine.com/article/hd-pentax-da-16-85mm-f3-5-5-6-ed-dc-wr-review...
The 16-85 resolution holds up better up to f/11.
Also consider that the 16-85 is a much more recent design, which no doubt helps.

Thanks John K; cannot argue with the facts

I use a K3.

The 16-50 is going back, with a new 16-85 coming the other way; 2nd time lucky I hope on that count.

Regards
Adrian
K5IIs, Sigma 10-20, Pentax DA 16-85, Pentax DA 55-300, Pentax 70 Ltd, Metz 44 AF-2.
Flickr: http://www.flickr.com/photos/ambott/
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