[OM] Re: What is backfocus?

[Chuck Norcutt]

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 Norcutt

Ali Shah wrote:
> Just wondered. When speaking of an AF lens - people
> talk about backfocus problems and other issues. Mainly
> quality control related things. What is backfocus and
> what other issues should be considered with AF lenses?
> 
> 
> 
> 
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