Focus Shift with 40mm f2.8 Sonnar

[Captain]

I recently borrowed an RF 40mm f2.8 Sonnar and the shots taken at 80cm showed a shift of focus of about 6 inches behind the set focus while Summicron/Rokkors didn't show this. Just wondering if others notice this?

 

[mfogiel]

It is probably not "focus shift" but a problem with the correct cam setting on the lens. Focus shift relates to the shift of the plane of best focus as you stop down, this is simply a focus misalignement respect to the lens cam. This can happen with any lens and can be easily corrected.

 

[Captain]

The lens focuses fine at infinity so if it was the cam as you say then surely it would also bee seen at longer distances?

 

[Hacker]

No such issue for me.

 

[Paul T.]

If the lens focuses fine at infinity, then back-focuses closer up at all apertures, then it's a cam issue.

If the back-focusing at 80cm varies with aperture, then you have focus shift.