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05-22-2013, 04:38 PM   #1
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Da18-135 Soft on RHS of image

This has really got me puzzled.

A few weeks ago I was out early in the morning with some of my photographer buddies seascaping. With the Da18-135 on K5 body and camera attached to a Tripod, I 1st noticed in one of my shots that the RHS of the image is soft. almost like

motion blur, So I rechecked the focussing and checked the Tripod that there was no movement in the head and continued shooting. in the process my images were still soft on the right hand side of the frame.

to give you some background :- the Da18-135 has been sent away to Pentax in Hong Kong twice now for AF issues and both times it has come back with no Fault with Lens . AF is ok

perhaps there is something wrong with my shooting style ? or may be the K5 needs Micro Fine adjustments to correct the AF.



Any comments or suggestions will be greatly appreciated .


Here is an Example ;






What am I doing wrong ?


Last edited by disco_owner; 05-22-2013 at 06:46 PM. Reason: Fixed the spelling and grammer
05-22-2013, 05:27 PM   #2
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It looks like one of the elements has become decentered, I dropped my first 12-24mm and this is what happened to it, so I ended up buying another.
This can be repaired. Good luck mate.

P.S nice shot Which beach is this?

Last edited by Skipen; 05-22-2013 at 06:05 PM.
05-22-2013, 05:51 PM   #3
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Wow that looks like a serious degree of decentering or whatever the problem is.

I had a similar picture with one edge fuzzy, but it was due to me handholding a split-ND in front of the 10mm, and sometimes getting the edge of the filter into the frame during the several-second exposure. Normally moving the filter isn't harmful of course - as long as it doesn't touch the lens, and the edges of the plastic filter stay out of the frame.

Paul
05-22-2013, 06:25 PM   #4
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All good suggestions. Is it only at one focal length?
It sounds crazy, but to confirm it is only on the one side, try taking a picture with the cam plus lens upside down (make sure the target is square to the sensor plane, like a block wall or something like that).
If at wide settings, this lens suffers quite a bit from field curvature as noted in Photozone's review.

Where was the focus point in the above shot?

05-22-2013, 07:06 PM   #5
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QuoteOriginally posted by Skipen Quote
It looks like one of the elements has become decentered, I dropped my first 12-24mm and this is what happened to it, so I ended up buying another.
This can be repaired. Good luck mate.

P.S nice shot Which beach is this?
The shot was taken at Avalon , and thanks for the complement.

your suggestion that one of the lens elements has been decentred is more likelyhoof the explanation. it has been suffering from AF issues since middle of last year and was has sent away to HK via Atech in Sydney to have it checked and repaired twice and both times it has come back with no fault found. AF is ok. but clearly it's not. yesterday afternoon I took it to Whiltons camera repaires and chris tested the lens. he tells me that the lens has intermitant focussing issues and cannot Nail focus on every shot. it is really frustrating.

QuoteOriginally posted by tibbitts Quote
Wow that looks like a serious degree of decentering or whatever the problem is.

I had a similar picture with one edge fuzzy, but it was due to me handholding a split-ND in front of the 10mm, and sometimes getting the edge of the filter into the frame during the several-second exposure. Normally moving the filter isn't harmful of course - as long as it doesn't touch the lens, and the edges of the plastic filter stay out of the frame.

Paul
Hi Paul , all my Square filters ( Lee ) are on the Foundation Holder which doesn't cuase any Vignetting or softness due to the edges of the ND 's or the Grad.

QuoteOriginally posted by Clarkey Quote
All good suggestions. Is it only at one focal length?
It sounds crazy, but to confirm it is only on the one side, try taking a picture with the cam plus lens upside down (make sure the target is square to the sensor plane, like a block wall or something like that).
If at wide settings, this lens suffers quite a bit from field curvature as noted in Photozone's review.

Where was the focus point in the above shot?
Not sure if this is occurring at different focal lengths , I usually shoot at the wide end with the DA18-135 for all my landscape shots unless I need to focus on a specific part of the scene where I zoom in a little.

I'll setup my camera at 0 Deg* and 180 Deg* and take shots and post them up with a Newspaper page and post up the results here . let me know what your thoughts
05-22-2013, 09:25 PM   #6
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QuoteOriginally posted by disco_owner Quote
The shot was taken at Avalon , and thanks for the complement.

your suggestion that one of the lens elements has been decentred is more likelyhoof the explanation. it has been suffering from AF issues since middle of last year and was has sent away to HK via Atech in Sydney to have it checked and repaired twice and both times it has come back with no fault found. AF is ok. but clearly it's not. yesterday afternoon I took it to Whiltons camera repaires and chris tested the lens. he tells me that the lens has intermitant focussing issues and cannot Nail focus on every shot. it is really frustrating.
That's a shame, are you using center point focus or auto point selection?

If it's auto point selection that would explain the intermitted focusing, as it could be selecting the portion of the frame that's effected by decentering to focus on.

If not, could the appearance of a shot having "off focus" just be the decentering and not a focusing problem at all?
05-22-2013, 10:18 PM   #7
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I set the Centre point as the Focus Point ,try and get a focus and take a shot but intermitantly images are soft.

just to illustrate , I found this Cutting speed chart from one of my old Fitting & Machining Handbooks but probably not the best chart for testing sharpness but it's all I could Find .


all the images were taken close up so there is quite a bit of barrel distortion.

18 mm F3.5


18 mm F5.6


18 mm F8.0


18mm F11


18 mm F16




-----------------

18 mm 3.5


18 mm F5.6



18 mm F8


18 mm F11


18 mm F16



In test chart 1 , the Bottom of the Images is out of Focus , but the top of the image is focus , camera was set up parallel to the plane of focus and the camera AF indication was that the lens is in focus with the image.

in the 2nd chart from the top the Numbers seem to be slightly out of focus but the rest of the chart seems to be ok

....

Clearly there is a problem with the focussing of this lens???? and it doesn't appear to be only on 1 side , from the first 5 images which the orientation is the same the softness is on top or bottom >>

Last edited by disco_owner; 05-22-2013 at 10:27 PM.
05-23-2013, 01:01 AM   #8
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Yep, it appears as though you have a huge issue with element misalignment.

05-23-2013, 04:53 AM   #9
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Good work - the fact you have one side of the image stronger than the other is a pretty clear indication of decentering of some sort.
As per Skipen's comment, and your observation, it looks like an element is not parallel to the sensor - however, if you didn't change the setup other than the aperture during shooting, I am scratching my head a but as to why the flip.

In terms of focusing adjustment, since the 18-135 is a slow lens, the center of the frame may be in focus and the corners out as a function of the DOF/field curvature. Since it is the top and bottom affected you may have some issues with this suggestion, but test the AF focus point by shooting the target above at 18mm on an angle. I'm looking at the line of focus across the frame.

Hope this helps.
05-24-2013, 05:05 AM   #10
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QuoteOriginally posted by disco_owner Quote
I set the Center point as the Focus Point ,try and get a focus and take a shot but intermittently images are soft.

just to illustrate , I found this Cutting speed chart from one of my old Fitting & Machining Handbooks but probably not the best chart for testing sharpness but it's all I could Find .


all the images were taken close up so there is quite a bit of barrel distortion.

18 mm F3.5


18 mm F5.6


18 mm F8.0


18mm F11


18 mm F16




-----------------

18 mm 3.5


18 mm F5.6



18 mm F8


18 mm F11


18 mm F16



In test chart 1 , the Bottom of the Images is out of Focus , but the top of the image is focus , camera was set up parallel to the plane of focus and the camera AF indication was that the lens is in focus with the image.

in the 2nd chart from the top the Numbers seem to be slightly out of focus but the rest of the chart seems to be ok

....

Clearly there is a problem with the focusing of this lens???? and it doesn't appear to be only on 1 side , from the first 5 images which the orientation is the same the softness is on top or bottom >>
I bought a Sigma 17-70mm f/2.8-4.5 over five years ago and it was soft on one side at 17mm f/2.8. My other (at that time few) lens had no such problem. So in my mind and to all logic it had to be the lens. After time went by I found my old K10D (really Samsung GX10; same as K10) was the culprit. The web has a lot of good articles and tests to show what I am talking about. The Pentax dSLR body sensor has three screws on the bottom that need manual adjustment with the aid of a computer. This aligns the sensor perfectly square with the back of the lens, kind of like a pan/tilt camera tripod head. You can be off in any direction. With it just on the edge of being in Pentax spec and the lens being just on the edge of being in Pentax spec it can add up to what you see above. Each time the camera gets a focus, a perfect focus to your eyes (which can't even come close to a perfect focus) it drifts. Its just best to read up on the subject of both body and lens problems and how a combination of both can cause this.

As I said, I threw a fit when Sigma said it was not my lens. They wanted my camera. I sent it to them. They sent back test pics showing the anomaly but I still did not believe it until my K10 died and was replaced under warranty and the Sigma lens was fine after that, as well as the other lens that were always fine! It was a combo of lens and body.

Here is one of the test patterns. I have more if you want to see them showing the affect. I am time limited now, but latter... Do note how lens companies are not interested in the deep corners. Its probably why when you send in a lens to get a soft corner fixed it comes back with a note saying its fine


Last edited by jamesm007; 05-24-2013 at 05:24 AM.
05-24-2013, 05:15 AM - 1 Like   #11
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That really looks like a tilted element or something, brutal.
LensRentals.com - A Tilted Element Demonstration
05-24-2013, 05:46 AM   #12
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I've only experienced this sort of soft edge once, on a Tamrom 17-50 that (I suspect) had been damaged in transit. Sending your lens back and forth to HK for the AF fix probably wouldn't have helped with the optics of the lens.

Can you shoot a test chart that is just a square grid of graph paper or something? It's hard to see the abnormalities from your test shots due to the irregularity of the target.

Alternatively, do you have some timber lattice on your verandah or something? That makes a good test target too.

Also your test JPG's don't really need to be 500kb each. The ones included here made this page about 5MB heavy and real slow.
05-24-2013, 04:28 PM   #13
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The first set of 5 x Images were all shot with the Camera in portrait on a Multirow Pano head , I've flipped the camera 180 and rotated the head 180 and shot the same test chart at Different F-stops on the 2nd set of 5 x shots

thought my illustration of the test chart is/was a good indication that the Softness is occuring at Different apperture settings on either side of the Frame ( RHS or LHS )

I'm not quite sure where the abnormalities are ???

Also In the First chart at F3.5 the Bottom of the Images is quite Soft ( LHS ) but it Flips on the 2nd image taken at F5.6 ( RHS ) and then repeats itself for the Next 2 shots and this is what I have noticed out in the field.

the Softness is More regularly on RHS of the image.

It could be possible that the Lens has been Dropped in transit ? who knows...

I have a Quote to get this Lens fixed by an independant camera repairer even though it's still under warranty.
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