Canon 24-70 II f2.8 has decentered elements or not?

[DaLiu]

Hi guys,

I need some help here, after checking some of my recent shoots with my Canon 24-70 II f2.8 on my Canon 5D Mark 4 I realized the lens is quite soft on the corners in some photos at f8, could you please check the attachments and express your opinion if I should send it back for fix?

 

[Loswr]

My iPhone isn't a place to judge sharpness, but if it's noticeably softer in one corner than the others, that's a sign of decentering. But often, an even easier way to tell is to shoot a clear blue sky or an evenly lit wall at max aperture, and look for asymmetrical vignetting.

 

[DaLiu]

Two more, on the other hand this one from Prague with the Charles bridge looks fine.

 

[kaihp]

Two more, on the other hand this one from Prague with the Charles bridge looks fine.

According to Uncle Rog, a quick & simple way to test for decentering is to shoot that Zeiss Siemens Star slightly defocused. If the lens has bad decentering, the defocus will look different to one side.

Reference: https://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover/

 

[hkenneth]

Two more, on the other hand this one from Prague with the Charles bridge looks fine.

According to Uncle Rog, a quick & simple way to test for decentering is to shoot that Zeiss Siemens Star slightly defocused. If the lens has bad decentering, the defocus will look different to one side.

Reference: https://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover/

I have a lens that centers differently than my other lenses yet its slightly defocused Zeiss Siemens Star looks totally fine. So is the lens decentered or not?

 

[YuengLinger]

It's no fun sending a lens to Canon for inspection and repair. It's also no fun bringing my car in for service when I suspect wheels need alignment. In any event, it's maintenance.

 

[fussy III]

It's no fun sending a lens to Canon for inspection and repair. It's also no fun bringing my car in for service when I suspect wheels need alignment. In any event, it's maintenance.

Good luck with the service! When I sent in my 24-105 L to CPS here in Germany for centering, it came back with even worth decentering three consecutive times. I wasted days on testing and evaluating the centering anew, a work that the service should have done. After these three attempts I sent it in once more asking them to NOT make any further attempts but instead simply check it and give me a refund for the repair (I would have sold it as defective).
They ignored that and without notice repaired it once more after which the lens was about as imperfectly centered as it was when I sent it in in the first place. At least they agreed each time that they had done a sloppy job and refunded me as a way of saying "sorry".
But looking back I would not consider sending in a lens (especially not a Zoom) for centering again but rather sell it and mention its imperfections in my adds.

 

[fussy III]

My iPhone isn't a place to judge sharpness, but if it's noticeably softer in one corner than the others, that's a sign of decentering. But often, an even easier way to tell is to shoot a clear blue sky or an evenly lit wall at max aperture, and look for asymmetrical vignetting.

The first example to me indicates that the lens in question is very badly decentered. What Neuro had to say about checking vignetting should suffice in that case. Decentering usually appears different at different zoom-extensions.

For a more subtle check, put your camera on a tripod, f5.6, live view, RAW, put a well outlined object at infinity into the center, focus manually, do not further change focus, then place object into all four corners at the same distances to those corners. If the lens is decentered, then in result there should be some obvious diferences between the corners in terms of sharpness, detail, aberrations. Deactivate all lens corrections in the RAW converter and apply only minimal sharpening if any. It's best to cut these corners and put them side to side in Photoshop into a single image, then check 1:1.
Do this process and comparison in the extreme focal ranges as well as in mid-focal-range.

But make sure not to choose backlit or conditions when thermal air movements may have an influence.

Best wishes

 

[DaLiu]

Looks like there is a real problem with the 24-70 @ 50 mm, i just compared with my cheap 50mm, here are the results. Pretty similar in the center but in the corners the 100E lens looks amazing compared with the 24-70, totally disappointing.