Do I have a bad copy of the 18-55?

Started 2 months ago | Questions thread
OP Keith Lommel Contributing Member • Posts: 740
Re: Do I have a bad copy of the 18-55?

Erik Baumgartner wrote:

Keith Lommel wrote:

Haven't been able to get out and do more thorough testing as some have suggested, but reviewing some old images I've found quite a few that are acceptably sharp across the frame, and then a few more like this one below:

This shot is quite sharp on the left, but really soft on the right side. Note in particular the steeple above the blue house and the black wrought-iron fence in front of the tan house. My initial thought was that this was a DOF issue, but at 21mm f/5.6 DOF should be very deep, especially since focus was on the gray building with the columns in the center. Hyperfocal would have everything from about 13ft to infinity in focus. With focus quite a bit further back from 13ft, everything behind that gray building should definitely be in focus. Notably, the black fence should be in roughly the same focal plane as the gray building. Also tellingly, the double gabled building behind the gray building is reasonably sharp as are the trees behind it, and it is further back than the blue and tan houses. So those should also be sharp.

Camera shake should not be an issue with a shutter speed of 1/900s, and f/5.6 is a stop and half down from wide open at this focal length, so the lens should be at its sharpest.

That said, OIS was on, so perhaps a malfunction in that system is the culprit? Can OIS cause just a part of the image to be blurry?

Where was the focus point? This looks like more of a DOF issue than anything.

Focus (confirmed by exif data) was on the gray building with the four columns in the center of the image. My initial thoughts were DOF as well, but how do you explain the inconsistencies I note above, such as the double-gabled building (and the trees behind it) being in focus, but the closer blue and tan buildings being blurry?

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