back focus problem with nikon mount ?

[Yann Bouzerand]

Hi,
I ve got problem with my nikoun mount and my two still zooms, i can't have the back focus right i m adjsuting it with the red one focal plane adjuster but i can't have focus, the only time that i have focus is when the lens is very close and i m very far from the subject, but it's still a little out of focus.

Any advice ?

[Robbie Anderson]

Your lens mount is too close to the plane of the sensor. The lens is focusing beyond infinity at the infinity settings and at the intermediate distance settings. That is why you are having to use a close distance setting on the lens to make the image sharp on an infinity object. Is it possible that your have been turning the backfocus adjustment in the wrong direction?

If it not possible to adjust the backfocus distance adjustment on the RED mount to make the infinity focus correctly then try a different Nikon lens. For the greatest accuracy in setting back focus it is best to use a wide angle lens as your test lens. The possibility exists that one of your Nikon lenses is out of adjustment, but it is unlikely that they are all incorrect. If all of your Nikon lenses have the same problem then the mount should be checked professionally on an optical bench.