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01-22-2012, 12:27 PM   #1
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Wondering if my Lens is Defective

I have a K5 and recently replaced the kit lens with a SMC DA 18-135mm lens and I have one heck of a time getting things straight with this lens, straight in the sense of objects I'm photographing. I have been shooting digitally for about nine years and have never had this sort of problem before. Unless I am totally head on straight forward, I cannot get a straight lines. Everything parallel with that line is distorted. I'm talking about shooting at 50-70 meter area. I do realize that any wide angle lines will distort, but I have trouble with this lens throughout the full range. I also shoot a Lumix GH2 and have no problems of this kind with that camera.

Here is a photo I took today. It was from my car, so I would expect 'a little' curve, but I noticed that this has a convex affect at the curb. This is definitely more extreme than any other camera I have used as I am doing exactly the same kind of shooting with my K5 as with the others (11 decent point-n-shooters plus a Canon Rebel XTi.) I was having this same problem also with my 18-55mm kit lens. The problem seemed to arise suddenly.

Could it be my camera?

Here is the photo. Dancin' the Night Away | Flickr - Photo Sharing!

I realize this isn't extreme but I have issues taking just about each shot, never any with my Lumix GH2.

01-22-2012, 12:44 PM   #2
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That's pincushion distortion.

Pentax SMC-DA 18-135mm f/3.5-5.6 ED AL [IF] WR - Review / Lens Test - Analysis
01-22-2012, 12:52 PM   #3
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It looks perfectly normal for this lens to be honnest ! Its a superzoom.... it suffers from heavy pincushion distortion at the wide angle end and barrel distortion
at the long end. It can be corrected in photoshop though if its spoiling the image. That particular pic would look ok though. Only you know that the curb was straight
in reality because you were there. A single lens covering 18-135mm is a tall order, so you can expect big compromises in most areas.
01-22-2012, 01:50 PM   #4
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QuoteOriginally posted by westmill Quote
Only you know that the curb was straight in reality because you were there.
I don't know about that. The dead giveaway is that the roof ain't straight either.

01-22-2012, 02:07 PM   #5
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QuoteOriginally posted by Ikarus Quote
I don't know about that. The dead giveaway is that the roof ain't straight either.
You should see some of the buildings where I live lol
01-22-2012, 02:13 PM   #6
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QuoteOriginally posted by TooLoose Quote
I do realize that any wide angle lines will distort, but I have trouble with this lens throughout the full range.
If you want to get rid of the distortion easily
without having to go through any PP,
and don't mind a slightly slower shooting rate,
you can always use the in-camera lens correction.
While I don't have the DA 18-135/K5 combination,
I've used in-camera correction on a K-x
with the kit lens for casual photography.
01-22-2012, 02:20 PM   #7
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It's apparently a known property of this lens -- it requires Lens Correction (either in-camera or via postprocessing) to avoid this. Try setting that and let us know if it makes any difference. (I've been interested in acquiring this lens but this issue has given me pause, and I haven't yet been able to borrow or rent the lens to try it out myself, so I'm keenly curious to hear...)
01-22-2012, 02:35 PM   #8
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I will try the in-camera correction. The funny thing is I have been using super zooms for a long time and have not had this problem to this extreme. A few of my Canon Power Shot S series (3S IS, S10 IS, S20 IS, and S30 IS (35x optical zoom)) and a Fuji HS10 (30x optical) worked fine for the kind of urban shooting I do.

I'm guessing (and breaking out in a sweat) that the solution is prime lenses or lenses with less zoom range. I don't have the bucks for that solution. I hope the in-camera method works, or at least minimizes it enough so it isn't so bothersome. The lens is very sharp and I was liking it just fine.

As I said before, I don't have this issue with my Lumix GH2 14-140 lens.

Other than one issue I have with my K5 (the memory card lid is too close and the card is really difficult for me to remove...I don't always have a pair of tweezers on me when I'm downloading pics) I am really enjoying this camera a great deal.

01-22-2012, 02:42 PM   #9
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QuoteOriginally posted by TooLoose Quote
A few of my Canon Power Shot S series (3S IS, S10 IS, S20 IS, and S30 IS (35x optical zoom)) and a Fuji HS10 (30x optical) worked fine for the kind of urban shooting I do.
I've been bugged by distortion on compact Canons,
especially barrel distortion at the wide end.

Let us know how the in-camera correction works for you.
It may slow you down if you try to shoot a rapid sequence,
but you can always turn it off in that situation.
01-22-2012, 03:35 PM   #10
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Use the in-camera correction as stated, and take a flat piece of sandpaper and sand your SD cards edges just slightly, both issues resolved. For whatever reason, the K7/K5's card chassis/slot IS just a slight bit on the tight side, but you'll only be removing a very small amount of plastic, all will be well.
01-22-2012, 04:20 PM   #11
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QuoteOriginally posted by TooLoose Quote
Other than one issue I have with my K5 (the memory card lid is too close and the card is really difficult for me to remove...I don't always have a pair of tweezers on me when I'm downloading pics)
Could you download via cable instead?
01-22-2012, 04:53 PM   #12
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I have the in-camera correction turned off, because it made my K-x way too unresponsive for shooting frames in rapid succession. It doesn't matter though, because PDCU will later perform the exact same correction on the PC.
01-22-2012, 06:03 PM   #13
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The difference between your superzoom P&S cameras and a dSLR is the ability to change lenses but with that comes variety in distortion. The superzoom P&S cameras, like my Panasonic ZS-5, always have their lens correction settings in operation because they only have one lens. The K5 allows you to turn that feature off to increase both the speed of the camera and your creativity when post-processing the photo. I leave mine on most of the time, but when I need bursts of multiple shots I turn it off and do the corrections in post-processing with LR3 or PS.
01-23-2012, 05:35 AM   #14
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Now I'm wondering why I don't have this problem with my Lumix GH2. Perhaps it has to do with the crop factor, the K5 at 1.5X and the GH2 at 2X? Or maybe Lumix has a correction feature installed and by default, on?

Can I expect this same issue with all lenses, Pentax and third party, for this camera?

Thanks for the help on this.
01-23-2012, 06:26 AM   #15
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QuoteOriginally posted by TooLoose Quote
Can I expect this same issue with all lenses, Pentax and third party, for this camera?
Check the lensreviews on photozone.de; they measure distortion (amongst other stuff).
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