AF Fine-tuning, plus Tips

Started Nov 10, 2010 | Discussions thread
Leonard Shepherd
Leonard Shepherd Forum Pro • Posts: 14,412
Re: Back in correspondence

newfounder wrote:

Auto Focus fine tune is really a great feature. I can't believe why many experts on web or in prints say in most case people should not use it at all.

I am back in correspondence after a delay with an emergency flight by helicopter to hospital with significant head injuries.

I am on the road to recoverer - and had intended posting this link that suggests a target that is usually good, and another that causes me mis focus with about 5% of my lenses
Anybody wanting the big 3.5 MB zip file - please be a little patient.

I am not aware of anybody saying fine tune should never be used - as distinct from making the point if you do not take the trouble to find out how AF works you are extremely unlikely to realise most "fine tune perceptions" are nothing to do with the lens.

That is why Nikon's guidance says "AF tuning is not recommended in most situations" and "may interfere with normal focus".

Nikon have a section on getting good results using auto focus in all camera instruction books, and in many lens instructions.
It does not mention using fine tune.

Nikon have a section under "Troubleshooting" in all instruction books and how to solve out of focus photo issues.
It does not mention using fine tune.

Nikon explain for those who care to find out in the camera guidance on getting good results using auto focus AF accuracy may be poor if
1/the subject has low contrast (the skin in a portrait can have low contrast)

2/ The focus point contains objects at different distances from the camera (45 degree targets are common examples of when this can happen)

3/ The subject is dominated by regular patterns (Nikon quote a row of windows - my testing shows targets like LensAlign can cause similar poor focus accuracy)

4/Subjects which contain areas of sharply contrasting brightness (Nikon suggest objects in half shade - my testing confirms high contrast lines can be similar

5/ Background objects which appear larger than subject (why AF sometimes prefers the background)

6/ The subject contains many areas of fine detail - Nikon suggest a field of flowers.

Moving on these types of lack of focus accuracy disappointments are nearly always because the photographer has not realized these issues are because AF with some subjects is not infallible.

When a good enough AF target has not been selected for accurate AF, manual focus and not fine tune is usually the solution.

Fine tune has a place if a body is well worn and in need of calibration, or as a possible solution pending repair of a dropped lens.

Fine tune does not have a place if the photographer does not know how to select a highly reliable AF target before investigating fine tune.

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Leonard Shepherd

Good photography is mainly about doing simple things well. The challenge is doing simple things well enough for good results.

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