That is a criticism of autofocus systems in general, not of the AF fine adjustment procedure.

The most accurate way to focus is to use live view. Either using the Contrast-Detect AF system, or by manually focussing and using the screen zoomed at 100%. This is because you are then detecting the focus point directly on the cameras sensor.

When using the viewfinder you are relying on the camera's Phase Detection AF system which has its own sensor. If the AF sensor and digital sensor are not in perfect alignment you can get back/front focus issues. Hence the AF Fine adjustment menu.

If your camera/lens combo is front/back focussing then using the AF Fine adjustment will correct this. It wont be as accurate as Live View, but it will be a heck of a lot better than not making the adjustment.

In my experience I have found that setting the Fine adjustment while focussing from about 3-5 metres ( on lenses below 100mm) gives me accurate AF at any focus distance. It is lens and camera dependent. So on my K1 most lenses required +7 to +9 to correct backfocus. One only needed +3 and one required +10

I use 3-5 metres away for lenses up to say 100mm , a bit further away for longer lenses. The important thing is to make sure that the AF centre point (which is all you should use) covers the target on your test chart with no ambiguity.

With zooms I test at the longest and the shortest. In my experience if you get the adjustment right for one position the lens/camera combination is correct at all FL. There is the risk that you have a "wobbly" element in your zoom but you should identify that during testing.

I use the test chart at the end of this article http://www.kscameraclub.org/docs/pdfs/focus_test_chart_edited.pdf

One thing to remember is that a single test is not enough. You should do about 10 tests for each lens, and redo them for each adjustment. Each time you test you should be making the lens autofocus from either infinity or closest focus distance....so put your hand in front of the lens so it misfocusses or manually turn the focus ring. You have to make the AF system work hard to get best results.

If you have not done this testing before you will be surprised at how innacurate the AF system can appear to be. You would expect perhaps that each time you get the camera to AF that it would always pick the same focus. Well have a look on your lens distance scale after the camera has focussed each time. Out of 10 attempts the majority should be showing the same position, but there will be a few that don't. This is why it is important not to rely on a single test but to base yoour adjustments on a "best out of 10"

Front focussing...... use minus adjustment

Not in London, but just outside, I would ring Alan Marlowe. http://www.cam-rep.co.uk/

He has done work on many lenses for me and I could not recommend him higher.

I had slight backfocus issues with my lenses on my K10 , but there was no official AF fine tune adjustment so I lived with it as it was minor.

The K1 is different. 100% view on a 36mp vs 10 mp is in a different league. The slightest difference is like night and day. The sensors of today are actually showing up how big the manufacturing tolerances are when it comes to sensor positioning/AF sensor positioning.

Either you are lucky that your lenses/camera are in perfect alignment, or (this is a joke)...you should have gone to specsavers !

Agree with john and Jon..... get the AF tuned and you will notice a difference.

Larger and larger sensors means we can see the limitations of AF systems on cameras more easily.

When you do your AF tests.....

Tripod/test chart/natural light if possible. Use the widest aperture only to do the tests. Do many tests for each lens, getting the AF system to focus from infinity or nearest setting each time.

Nice set John.

Great set, thanks for sharing.

The first is my favorite.

Agree with all the comments...very nice. We have to make use of the current wet weather !