0

Over the last few months I've been noticing an annoying back - focus problem on my Nikon D7000, regardless if I was using a AF-S or AF lens. But the problem seems to happen more often on my 35mm 1.8G and on my 50mm 1.4D.

Recently I've found that I could fine tune the focus to try to solve this problem, and I've even used a test chart for sharpness and made tons of tests on an one meter distance from my object. After I've analyzed the results I've set my 35mm to -20 and my 50mm to -5 on the AF Fine Tune menu.

It worked just fine on my chart, but when I took my camera to test with "real world applications", once again I had tons of pictures with back-focus...

I've found this post which that guy seems to be having the same problem as I am. But my question here is:

  1. Can this problem be solved solely by tuning the auto focus? If so, which are the optimal values for my lenses?
  2. Can this be caused by something else on the camera?

P.S.: This is unlikely to be a lens problem, as I've tested the 35mm on a D3100 and my 50mm is brand new... And the problem also happened with a borrowed 50mm 1.8 D.

marked as duplicate by mattdm, MikeW, John Cavan Sep 13 '15 at 21:15

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

When doing AF Fine Tune (Nikon) or AF Micro Adjustment (Canon), the test distance should be as close to possible as the distance you plan to shoot in "real world applications".

At the very least, you should probably use a distance that is 25x the focal length of the lens. 50x is even better when possible (very long lenses make this problematic in a controlled setting - a 500mm lens would require a lab 25 meters/80 feet long!). For shorter lenses such as your 35mm and 50mm, you should test at the distance you shoot at the most with each lens. This may mean you need a larger test target than the one you used at one meter.

There is also the possibility that your "real world" results may reflect the difference between the focus points as depicted in your viewfinder and the actual area of sensitivity for that focus point. This answer to another question details the focus maps for a couple of Canon cameras, but the situation is similar for all of the modern multi-point phase detection AF systems from various camera makers: the actual areas of sensitivity are larger than indicated in the viewfinder and often overlap considerably. The area of highest contrast within any active focus area will be what the camera attempts to focus, even if it is at the edge and not the center of an active focus area.

For more on the advantages and disadvantages of various testing methods see:
Which offers better results: FoCal or LensAlign Pro?

For tips and varying perspectives see:
http://www.the-digital-picture.com/Photography-Tips/af-microadjustment-tips.aspx
https://photographylife.com/how-to-calibrate-lenses
http://charlesbushphoto.com/blog/2013/5/7/focus-fine-tuning-a-tool-in-the-battle-for-sharp-images
http://regex.info/blog/photo-tech/focus-chart
http://www.canonrumors.com/tech-articles/this-lens-is-soft-and-other-myths/

Not the answer you're looking for? Browse other questions tagged or ask your own question.