Why can a camera have backfocus issues with a single lens only, but not others?

Started Mar 8, 2014 | Questions thread
Shop cameras & lenses ▾
ForumParentFirstPreviousNextNext unread
Flat view
Regular MemberPosts: 266
Why can a camera have backfocus issues with a single lens only, but not others?
Mar 8, 2014

Why is it possible for a DSLR camera to show back or front focus problems with a single lens only but not other lenses?

One day out of curiosity, I checked my lenses, and with one of them (only one) the camera is clearly and reproducibly focusing behind the target. How is this possible? I assumed that the AF sensor adjust focus precisely at its location. If the length of the optical path to the AF sensor is different from the path to the image sensor, then the camera will focus in front of or behind the target consistently regardless of what lens is used.

What I do not understand is why this can happen with one lens but not the others.

I understand how a split prism focusing screen works, and I believed the autofocus sensor to work the same way. Based on this knowledge I can't see what could cause this problem to appear only with a certain lens.

I did find some forum discussions on the topic, but there are lots of guesses and clear misinformation out there.  Most photographers don't seem to have a good understanding of either optics or the inner workings of their camera (well, this is not really necessary for taking good photos ;).  I'm hoping to get a correct answer here.

This question has not been answered yet.
ForumParentFirstPreviousNextNext unread
Flat view
Post (hide subjects)Posted by
ForumParentFirstPreviousNextNext unread
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow