davidbicho
Aktiv medlem
Ramlade på följande beskrivning av fokuseringsproblemen(?) på Canons 50/1.2L (en tråd på dpreview) som lät sådär initierat att jag är nyfiken på om någon hört något liknande för denna glugg (som jag har haft inlämnat för backfokusproblem ett par gånger):
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The 50L experiences a focus shift for close subjects with the lens stopped down. The shift is worse when the subject is at about 3 feet and the aperture is at f/2.8. Beyond this the focus shift begins to be outweighed by the increasing DOF. Depending on your copy and the calibration of your particular lens/body combination the focus shift might be manifested by the intended focus plane being slightly forward of the actual DOF under these conditions. It appears that for well calibrated lens/body combos the intended focus plane is slightly within the front end of the DOF. The focus shift is still there but not noticable unless you're really looking for it. (note that there have been reports that on some bodies the 50L does exhibit the focus shift)
The above applies when using the center AF point. One of the work arounds discovered was that using the outer AF points tends to correct for the focus shift. There is a post here on dpreview somewhere describing what is occuring with this. I have had good success with this technique and it increases the number of keepers I get when shooting in the focus shift region. The only shortcoming is that, at least for my body, the outer AF points aren't as sensitive as the center AF point.
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The 50L experiences a focus shift for close subjects with the lens stopped down. The shift is worse when the subject is at about 3 feet and the aperture is at f/2.8. Beyond this the focus shift begins to be outweighed by the increasing DOF. Depending on your copy and the calibration of your particular lens/body combination the focus shift might be manifested by the intended focus plane being slightly forward of the actual DOF under these conditions. It appears that for well calibrated lens/body combos the intended focus plane is slightly within the front end of the DOF. The focus shift is still there but not noticable unless you're really looking for it. (note that there have been reports that on some bodies the 50L does exhibit the focus shift)
The above applies when using the center AF point. One of the work arounds discovered was that using the outer AF points tends to correct for the focus shift. There is a post here on dpreview somewhere describing what is occuring with this. I have had good success with this technique and it increases the number of keepers I get when shooting in the focus shift region. The only shortcoming is that, at least for my body, the outer AF points aren't as sensitive as the center AF point.
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