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11-07-2012, 01:15 PM   #1
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Out of focus spot on DA 18-55

Hello All,

I have the 18-55 DA kit lenses that came with my K-r in addition to my 55-300 and old 50MM F2. I've had the lenses about a year and a half and it's developed what seems to be an out of focus area on the left side of my pictures in landscape orientation. It's off center about halfway to the edge of the frame and seems to be about
midway down from top to bottom. Items around this spot appear to be focused correctly. Anyone had an issue similar to this?

Thanks,

Phothog

11-07-2012, 01:17 PM   #2
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How have an example?
11-07-2012, 01:26 PM   #3
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Out of Focus spot DA 18-55

Here's one, look at the person on the left of the picture compared to the person on the right.
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11-07-2012, 02:44 PM   #4
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Based on that photo, it's hard to say- it could be the fact that you're shooting wide open and the highlights are causing some distortion.


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11-07-2012, 03:12 PM   #5
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Um, could be a smudge on the front or the back element. Also, do a proper test. And keep in mind that the focus area is not a straight plane, its actually bent.
It could be a decentered lens element - has the lens fallen or been rattled lately?
11-07-2012, 03:12 PM   #6
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Hey Adam, Thanks for looking, I realize I was shooting wide open when I posted, however I have another example that doesn't have the highlights coming in
on the left. Perhaps this will be a better example of what I'm seeing. Look at the lady seated at the left in this picture. To me, the right side appears to be in focus but
when you get to her on the left it looks slightly out of focus.
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11-07-2012, 03:45 PM   #7
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Looks that way. Unless there is goo on the rear element or it is mounting improperly, probably de-centered.

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11-07-2012, 04:07 PM   #8
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Hi Na Horuk,

I cleaned both front and back before taking these photos for a friend of mine so they were clean and it was mounted properly. However, the lens has had some bumps in the past but it wasn't that recently. Maybe a small bump lately compounded some of the larger bumps in the past. Thanks for taking a look.

11-07-2012, 04:13 PM   #9
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VonBaloney, Thanks for the feedback as well, I was afraid that it might be decentered. These are not the usual photos I take, generally it's nature photography and sometimes in rough and remote locations. I know that when I first purchased the kit the lenses was sharp across the frame and lately I noticed a bit of blur that wasn't there before.
11-07-2012, 04:15 PM   #10
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Do the "donut" test with those charts in the link from previous post. You can do it quick and dirty just putting the chart on a monitor (possible enlarged). Not conclusive if it fails on a zoom lens (unless someone else can confirm it should pass with that lens, which I no longer have), but if it does pass the test then maybe some other explanation.
11-07-2012, 04:32 PM   #11
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I would suspect decentering as well. Notice how the background is in focus behind the woman, and OOF behind the man. Luckily, the 18-55 kit lens is pretty cheap (esp. a used one) if you need to replace it.

edit: I think civiletti's answer below may be correct. Seems one or more elements of the lens have tilted, possibly from being dropped or taking a hit somehow.

Last edited by paulh; 11-07-2012 at 05:22 PM.
11-07-2012, 04:32 PM   #12
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On the first photo, it looks to me that you lens/camera has a slight BF, the person on the right at the edge of the focus range; see the tree at the back which is also appears to be in focus.

On the second photo, it appears you have the focus selected point on the right. Again, the person on the far left is slightly in front (based on focus point selected); again, same thing apply there, therefore, appears soft. The decentering problem as I was told by Pentax can only be validated with focus point selected in the center.
11-07-2012, 05:09 PM   #13
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VonBaloney,

I zoomed the Zeiss chart on B&H photo and took a couple of snaps of it on my monitor, I can't say the results were conclusive, the center donut in one appeared to
be shifted slightly up but I'm not positive if it was just me trying to achieve the correct amount of focus blur.

Paulh,

I noticed the background as well, the grass behind the bench on the left appears to be more in focus than the background on the right.

aleonx3

Your observationsregarding the areas that appear to be in focus match mine. The camera was set to AF.S with Auto 11 for the focus point.

Thanks for everyone's feedback and suggestions.

Phothog
11-07-2012, 05:15 PM   #14
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It looks like the plane of focus is tilted. Perhaps you can exploit this trait in some photos.
11-07-2012, 06:00 PM   #15
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Its like a budget tilt shift lol The kit lens is fortunately cheap to replace and even the WR version can be had at a very reasonable price.
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