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Next PZ lens test report: Tokina AF 50-135mm f/2.8 AT-X Pro DX
#4
I would like to take this chance to ask a question about focus shift since it is mentioned above. I understand the meaning of "stop-down" type focus shift, which is presumably caused by the spherical aberration of the lens. But there seems to exist another kind of focus shift: the focus shift when the lens is wide open. And, from what I read from the internet, this kind of focus shift can arise either from the malfunction of the camera (e.g. the foucus sensor in the camera is not properly aligned) or from the lens. My question is: how can this wide-open focus arise from the lens? If the focus sensor is perfecly algined then what you see in the OVF is what you get in the image sensor--the essense of SLR. So, what kind of problems with the lens can make the precise AF system of the camera think that the image is in focus while the image on the sensor plane is not in focus?



Thanks,

Frank
  


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Next PZ lens test report: Tokina AF 50-135mm f/2.8 AT-X Pro DX - by frank - 07-05-2012, 09:05 AM

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