At 05:19 PM 6/21/2007, Chuck Norcutt wrote:
>Backfocus = the lens is focused behind the subject.
>Frontfocus = the lens is focused ahead of the subject.
>
>But I've never really understood why this is considered a fault of the
>lens. The lens is delivering the image and the camera is making
>contrast measurements and directing the lens to move forward or back and
>ultimately tells it to stop moving when the camera has decided that the
>focus is good (or good enough). Perhaps the lens coasts a bit while
>moving and doesn't stop fast enough when told to. But that would also
>mean the camera body didn't double check the final focus. Inquiring
>minds want to know more.
Chuck,
I don't know how the systems function but, at least with Canon, both
the lens and the body require calibration. Up until I purchased a
Canon 100/2 I hadn't had any AF problems but that lens, out of the
box, front focused by ~9" over 25'. I sent it to Canon service in
New Jersey and it came back working fine.
The party line at Canon is that they won't calibrate a given lens and
body together. Bodies are calibrated to a master lens and lenses are
calibrated to a master body. That way you avoid screwing up the AF
on several lenses that had been previously working (as described
about a D200 in another message ). I would think that Nikon's
standard procedure would be similar to Canon's. Makes me wonder if
someone screwed up at the service center in the case of the D200.
I did read at message once from someone that said a technician at a
Canon service center told him that he had calibrated the customer's
body and lens together. Who knows what a given technician may do or
say to get an irate customer off his back.
Later,
Johnny
__________________________
Johnny Johnson
Cleveland, GA
mailto:jjohnso4@xxxxxxxxxx
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