How badly decentered is my Sony 24-105mm f/4 G lens at 70mm?

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Platographer Contributing Member • Posts: 801
How badly decentered is my Sony 24-105mm f/4 G lens at 70mm?

When I got my Sony 24-105mm f/4 G lens a few months ago, I tested it for decentering on my Sony A7Riv and was satisfied. However, that was because I did not realize that it could be decentered at one focal length and not at shorter and longer focal lengths. So, although I noticed the left side seemed soft around 70mm during my test, since it was fine at 50mm and 105mm, I figured my testing technique was to blame and didn't really think much more about it. However, I have now exhaustively tested this lens at 70mm and it seems to me to be badly decentered there. While the scene I used to test it is not ideal since it is not perfectly flat, I tried dozens of shots using manual focus and dozens more using autofocus at different points on the left side and they all confirm decentering. I was extra careful to keep the plane of the camera as parallel to the stone wall as possible. Below are representative examples of the results at 50mm and 70mm f/6.3 when focusing on the left side of the scene. The 50mm photo is very sharp, but the 70mm is very soft on the left side while very sharp everywhere else. Again, I have replicated this result over about 100 shots using all different kinds of focusing points and both MF and AF, so this is not a focusing issue. Stopping down to f/8 noticeably but only mildly improves the left side at 70mm--it's still soft.

How bad is this decentering when viewed at 1:1 size? Also, how is it possible for a zoom lens to be noticeably decentered in the middle of its focal range, but not at the shorter or longer ends?

Sony 24-105mm f/4 G at 50mm f/6.3

Sony 24-105mm f/4 G at 70mm f/6.3

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