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My photos, taken with a Sony A6000 with a Sony E 18–200 mm lens, are unsharp on the left at moderate zoom and unsharp everywhere off-centre in severe zoom. This effect is present with image stabilisation on or off and with various aperture sizes.

This photo was taken at 43 mm, F/8. A far left crop is blurry:

crop from far left of image

But a far right crop is sharp:

crop from far right of image

Full photo here.

Photo with 200 mm, F/13, crop in centre is sharp:

centre crop image

Crop at far left is unsharp:

left crop image

Crop at far right is unsharp:

right crop image

Do these photos indicate a lens problem, or am I expecting too much from my gear, or could there be another problem?

Related: Sony SEL 18-200mm very blurry at the right part of the photo, Sony A6000 blurry in peripherals despite sharp center -- is this a mirrorless thing?

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    definitely a lens problem, might want to double check that its mounted properly on the camera though – user5359531 Mar 2 at 2:37
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    Might want to show the whole image for reference.... – rackandboneman Mar 2 at 22:57
  • @rackandboneman There is a "full photo here" link under the second crop. – gerrit Mar 2 at 22:59
  • Looks indeed slightly decentered to me, but still within what might be considered acceptable in a semi-pro wide-range zoom... does not ruin the picture when displayed full screen without further magnification.... – rackandboneman Mar 2 at 23:04
  • @rackandboneman Not noticeable without zoom — until I got my 4k screen ☺ – gerrit Mar 3 at 8:33
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Sony lenses have a reputation, particularly among the lower priced ones, of fairly sloppy alignment between the various lens elements. Roger Cicala, founder and lens guru at lensrentals.com, refers to it often enough. Such issues will always be compounded with zoom lenses as compared to prime lenses.

The wider the ratio between the shortest and longest focal lengths, the harder it is to make a lens perform optimally throughout the zoom range. Most high quality zoom lenses stick to a ratio of 3X or less, such as 24-70mm or 70-200mm workhorses. If all of the zooming is at telephoto focal lengths, one can stretch that to about 4X, such as with 100-400mm or 150-600mm lenses.

With lenses that start out at very wide angles of view and zoom all the way to telephoto territory, it gets more difficult. Your 18-200mm lens has a greater than 10X zoom ratio and starts out at 18mm. That's a tall order for a lens at any price. To do it and sell such a lens for only $750 makes it that much more difficult.

But it's not just Sony. Zoom lenses in general have a much steeper hill to climb when compared to prime lenses. A minor alignment issue might not be detectable looking at moderate enlargements from a prime lens or from the "best" focal length of a zoom lens. But when the zoom lens starts moving various elements around those issues can be magnified and become more noticeable. For the vast majority of zoom lenses, the longest extreme of the focal length is also where the optical performance is poorest.

Roger Cicala has written a few blog entries that discuss these issues, which include the following:

Painting Zoom Lenses with a Broad Brush – Roger’s Law of Wide Zoom Relativity
Things You Didn’t Want to Know About Zoom Lenses
There is No Perfect Lens

While there are probably "better" copies of the Sony SEL18200LE out there, they're probably not that much better, and there are plenty that are worse than yours.

Do these photos indicate a lens problem, or am I expecting too much from my gear, or could there be another problem?

You are expecting a lot from a zoom lens with a greater than 10X focal length range that sells for about $750. If you want pixel peeping sharpness, go to higher end zooms with narrower zoom ranges or, even better, use very well corrected prime lenses, such as this $4,600, 2.5 pound, Zeiss Otus 85mm f/1.4 or a Zeiss Otus 55mm f/1.4 Distagon T*.

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  • How do superzoom compact cameras fit in this picture? The Panasonic Lumix TZ95 ZS80 apparently has a 24-720mm f3.3-6.4 lens. Is it easier to zoom over a larger range with a smaller sensor (Lumix TZ95 has a 28.50 mm² sensor and a crop factor of 5.64, whereas Sony A6000 has an APS-C-sized 370 mm² sensor and a crop factor of 1.5)? – gerrit Mar 2 at 8:58
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    @gerrit That "24-720mm" lens is the 35mm equivalent description. The actual focal length of the lens is about 4.25-128mm. It's cheaper to make smaller lenses, but image quality is sacrificed when the smaller image is magnified more to view at the same size as an image from a larger sensor. In many cases the limitations of the smaller sensor and the required detail destroying noise reduction will hide the deficiencies of the lens because the entire field is blurrier. – Michael C Mar 2 at 22:30
  • Thanks for the good answer with links going into wonderful detail. I talked to a shopkeeper today, and he said that although one shouldn't expect perfect performance, it also shouldn't be nearly as bad as what I'm seeing; in particular since my images are much worse on the far left than on the far right. There's a lot of room between pixel peeping sharpness and the performance I'm observin.g – gerrit Mar 2 at 22:58

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