Sunday, February 12, 2012

D7000 back-focus problem

Nikkor 80-200mm f/2.8 ED AF-D
I have been using the D7000 for over a year and never thought of this problem.  After purchasing a Nikkor 80-200 f/2.8 AF-D, I realized the D7000 has been reported to have back-focus problems with this lens when shot with AF between 135-200mm through the viewfinder within a short distance from the subject.  The lens deliver tack sharp pictures and a nice bokeh.  Focus is spot on when focus is performed manually or through the D7000 live view--just not through the viewfinder.  Apparently, when live view is used, focus is performed using a contrast algorithm whereas when the viewfinder is used, focus is performed using some phase detection algorithm.  The D7000 has an AF Fine Tune control to correct these problems, but it does not help in the case of the 80-200mm lens however.  I set it to -20, the maximum setting for correcting back-focus problems, but it is not sufficient for the correction--see the picture below.  Rats.  Now, I wonder if I should sell it or just use it in manual mode or use live view.  The pictures do come out tack sharp!

Back-focus problem of D7000 with Nikkor 80-200mm:
"Hiding" is supposed to be the centre of focus.
Now, while I was already playing with the back-focus problem, I decided to test all my other lenses.  It looks like the Nikkor 18-200mm lens has a slight back-focus problem too.  It needs some AF Fine Tune adjustment of -8 or so on my D7000.

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