Decentered 24-70mm GM ii

coastlight · Jul 28, 2022

It's a sad post to make, but I have found out recently that my 24-70mm GM ii most likely is decentered. I got suspicious after looking at some landscape images at 100% so went out and shot some tests of a flat wall. It's the top right corner. It's worst at 70mm f2.8 so I'm attaching a full-size image at that setting for your inspection. The return window for me is already closed, but I hope for some advice as to how to proceed.

QuietOC · Jul 28, 2022

If it only effects a corner that would be tilt, which could be caused by the camera, not the lens.

JohnNEX · Jul 28, 2022

I know this feeling well - I also test for decentering and have both returned and kept lenses.

Mostly when people post up test shots the reply is, "you did the test wrong", so be prepared.

Did you take the test shot on a tripod with the timer and OSS off?

And never remove the exif data. What was the camera, shutter speed, ISO etc.

If you want to test for decentering, then this process is better than using a flat wall:

How to check how decentered your lens is - phillipreeve.net

How to check if your lens is decentered? You may have already heard of sample variation or decentered lenses. In this article we will show you how to easily test your lenses for proper centering. If you know how it works it will take you less than 5 minutes per lens! Where this test originates …...

phillipreeve.net

Remember that all lenses are decentered, the question is by how much.

101Colors · Jul 28, 2022

You really need to do more complete testing and post other examples.

One sample pic posted, a new user with 1 post & call it 'decentered' is not going to help others assist you . :-(

.

--
//////// Sometimes it's better to be kind than to be right. \\\\\\\

bpatient · Jul 28, 2022

coastlight said:
It's a sad post to make, but I have found out recently that my 24-70mm GM ii most likely is decentered.

FWIW, I believe that Roger Ciala of LensRentals once wrote something to this effect: 'I've tested [large number] of zoom lenses, and the frequency of perfectly-centered zoom lenses is less than 1/[large number.]'

coastlight · Jul 28, 2022

Thanks to those who replied so far. Still curious as to how you see the picture I posted though. To me the upper right corner is clearly soft and it’s pretty significant, more than I’d expect for such an expensive lens.

I’ll try some of the suggestions by JohnNEX and post back here. If I’m somehow wrong about this I’d be delighted, really don’t want to go through an exhaustive repair/return process if I can avoid that. But there’s of course a reason I paid for this lens over Sigma etc, and it’s hard to accept a flaw in this one.

AlephNull · Jul 28, 2022

bpatient said:
coastlight said:

It's a sad post to make, but I have found out recently that my 24-70mm GM ii most likely is decentered.

Click to expand...

FWIW, I believe that Roger Ciala of LensRentals once wrote something to this effect: 'I've tested [large number] of zoom lenses, and the frequency of perfectly-centered zoom lenses is less than 1/[large number.]'

It is impossible for a zoom to be perfect at all focal lengths. The question is whether the convenience of the zoom is worth putting up with the imperfections / aberrations.

To forestall the impression that I’m advocating for primes, no prime is perfect, either. Designing a good prime is somewhat easier, because you are only coping with one focal length.

Every lens has aberrations; the question is whether they are visible / annoying in the images you shoot.

Jeff2013 · Jul 28, 2022

I agree with a previous poster that is likely lens tilt. I’m sure that it is within factory spec.

I have tested a ton of zooms and yours really is not out of the ordinary, comparatively speaking, I would take a test shot where you focus on the ‘bad’ corner. If this negates any field curvature and you get greater sharpness, then eyes, or any subject matter, placed toward this corner should be sharp.

99% of users would likely be happy with this lens. The problem is that you know about the flaw.

--
Jeff
Florida, USA
http://www.gr8photography.com

jc1962 · Jul 28, 2022

You are correct. That photo is unacceptably soft in the upper right corner. If you have another lens try a similar test and see if that lens also produces a soft image in the upper right hand corner. I had a brand new Olympus camera about 10 years ago which had a defective sensor and regardless of the lens used it was always soft along the top center of all images. In my case it was the sensor. If another lens does not have that issue I would say that the 24-70mm lens is the problem. Do yourself a favor and get the lens fixed.

101Colors · Jul 29, 2022

~~I'm curious if you bought this lens new or not ??~~ Disregard. - probably very few used one's on the market yet... duh

Sure, a high dollar purchase should perform 'better' than a lower price lens ( well that's what we are led to believe anyway ).

coastlight said:
Thanks to those who replied so far. Still curious as to how you see the picture I posted though. To me the upper right corner is clearly soft and it’s pretty significant, more than I’d expect for such an expensive lens.

I’ll try some of the suggestions by JohnNEX and post back here. If I’m somehow wrong about this I’d be delighted, really don’t want to go through an exhaustive repair/return process if I can avoid that. But there’s of course a reason I paid for this lens over Sigma etc, and it’s hard to accept a flaw in this one.

--
//////// Sometimes it's better to be kind than to be right. \\\\\\\

Robjwilli · Jul 29, 2022

Send it to Sony for them to fix it.

4Photos · Jul 29, 2022

Also make sure to repeat test with other lenses under very controlled conditions. There was a recent post in this forum a few weeks ago, where it turned out that all lenses showed slightly less sharpness on one side, compared to the other (depending on focal length and DOF more or less easy to determine).

So the conclusion was that it was the camera body, not the lens in itself.

Dspider · Jul 29, 2022

also turn the camera upside down and shoot the same composition

that will confirm decenting.

Ds

Jeff2013 · Jul 29, 2022

Robjwilli said:
Send it to Sony for them to fix it.

I have done that, twice, over the years, with a similar level defocus. Both times they sent the lenses back saying that they were within factory specifications.

Of course, the lenses now go to Precision Camera Repair where they have no ability correct this type of malady since it could be related to bad lens elements, mounting alignments and/or improperly bonded elements. As I see it, the only recourse would be to attempt to contact Sony management and work one's way up the chain of command. I would contact the dealer that sold you the lens and see if they can facilitate such communication with Sony.

coastlight · Jul 29, 2022

Doing some more thorough testing now, will post results later. Can already say that the corner looks pin sharp (at 70mm f2.8) when i put the focus point in that corner. Don't know if I should take that as positive or negative...

JohnNEX · Jul 29, 2022

I should have added that there wasn't much difference between the top right and top left corners to my eyes.

I tested a new Tamron 70-180 today. The corners were a little different, but nothing drastic, so I won't return it.

samsonleePhoto · Jul 29, 2022

my experience with Batis 85 :

I took focus on any flat surface at the middle,

the left hand side was often soft

(portrait mode : the upper half was very soft).

Zeiss Far East sent it to Japan for inspection

They would adjust it for me and I must pay US$205

though under warranty.

The whole process might take 3 months (mid-May to Aug)

By the way,I live in Hong Kong. No sole agent for Batis lenses here.

Tristimulus · Jul 29, 2022

Most lenses have field curvature.

For flat objects better use a flat field lens like a macro lens.

4Photos · Jul 29, 2022

Tristimulus said:
Most lenses have field curvature.

True, but it would be symmetrical.

coastlight · Jul 29, 2022

Did the test in line with the method recommended by phillipreeve.net. Here's the result at f2.8:

ISO100 1/250s f2.8 70mm

And at f8:

ISO100 1/125s f8 70mm

All 100% crops, view at original size.

Decentered 24-70mm GM ii

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