Sony decentered lenses vs focusing

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Trk Regular Member • Posts: 228
Sony decentered lenses vs focusing

Recently I have been selling and buying Sony lenses and other buyers pointed out that Sony has no quality control and there is a lot of decentered lenses. I did not believe this at first but I noticed issues with new Sony 85mm F1.8 lens and eye focusing.

Typical result of eye focus was

Eyeball is at 15 mark, focus is at 14.

It looks like it is ok but it is not, image is not sharp where it should be, camera is front focusing.

Correct focus

In the end after reading Fred Miranda decentering test protocol

https://www.fredmiranda.com/forum/topic/1534737/0

and article from lens rentals

https://www.lensrentals.com/blog/2012/09/the-effect-of-a-decentered-lens-on-autofocus/

I realized that this struggle is probably because of lens decentering, I returned lens several times until I got good copy.

Decentered copy

Left upper corner vs right upper corner (massive crop)

Good copy

Left upper corner vs right upper corner (massive crop)

I do not have rigorous tests results but good lens eye focuses correctly more often, whereas decentered lens misses focus more often. This is on a7r II which does not have as good focusing system as newer models.

From couple of tests it looks like that with good lens first photo is almost always correctly eye focused whereas with decentered lens it was not.

This means that while having a7r ii I will not buy any zoom lens because Mr. Cicala from lensrentals wrote in some forums that no zoom lens is perfectly centered. And a7r ii just does not (eye) focus correctly with decentered lenses.

It looks like huge percentage of Sony lenses at least in my country are decentered. However, I cannot be sure whether it is Sony QC issue or rough handling from retailers.

So my recommendation now is always return all decentered lenses (must for a7r ii which cannot handle this).

 Trk's gear list:Trk's gear list
Panasonic Lumix DMC-GM1
Sony a7R II
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