Spent a bit of time using the Lens Fine Tuning feature on my Z50II.

[monte12345]

The lens in question is the Sony Mount 17-70mm f2.8 with the Viltrox E to Z adapter. So it's not totally unexpected that using this feature is necessary.

Notes on the camera settings for the AF. First up all of my cameras are setup for Back Button Focus. Mode was AF-S and the focus area selected was the Pinpoint area. The lens does do a lot of hunting with this particular focus area but it will provide a focus confirmation with the focus usually close enough for horseshoes. If you zoom the viewfinder to 100% and then re-focus from that point it will dial the focus into a single repeatable point. With the larger AF areas the repeatability approaches 100%, so this isn't lens issue it's a result of using a very tiny spot to focus and I suspect that camera movement comes into play here even when you are using a tripod.

Prior to today I had not a clue that zooming the viewfinder will allow the AF to refine the focus but it will do that and it also works on my Zf so I expect that this hidden feature is available with every Expeed 7 model. At some point I will get out my Z7II and see if this focus refinement is possible with that camera. Those looking for pinpoint accurate focus may not need to use manual focus to get it spot on, all they need to do is hit the AF On button again after zooming the viewfinder.

Below are a couple of images getting that Tamron as close to spot on as I was able to. These are actual screenshots of the images at 300% peep and the differences are quite subtle but I finalized on the +9 setting for Tele. I will also note that I've been watching this nest and it's already produced 3 live chicks that have fledged and left and this is the second set of eggs in this nest this year. BTW, this particular Robin is much calmer about "intruders", the previous Robin would flee the nest as soon as he saw me.


Wide -2 & Tele +6


Wide -2 & Tele +9

BTW procedure was rather simple. Put the camera on a tripod and choose a detailed target to focus on. I chose this particular target because it's much more interesting than a brick wall and I wanted to get some pics of this Robin. It's also why I chose the pinpoint focus area. Shooting the brick wall would have allowed a larger focus area. The drill was to focus on the target and then refine the focus manual with the viewfinder zoom to 200%. The direction of the focus movement is what determines if you need to do positive or negative. Keep repeating this until you get to the point where you don't need to refine the focus to get it spot on. BTW this adjustment is stored for this specific lens so anytime you mount the lens this tuning will be used with that lens.

 

[Leonard Shepherd]

IMPORTANT in my opinion - have you chosen a target suitable for checking focus accuracy?

The fine detail on the nest almost certainly has too little detail for accurate AF.

Mirrorless AF when it does not detect an identifiable subject only detects detail parallel to the short dimension of the frame and usually the closest detail with reasonable contrast.

If this happens AF is likely to concentrate on the vertical mortar joint to the left of the bird - which is not in the centre of the image - indicating a fine-tune near focus adjustment that in reality does not exist.

With a bird detect AF system if the AF detect the birds eye - in this image the eye is slightly right of centre and could indicate a slight fine-tune far focus situation that in reality does not exist.

Sorry – fine tune and targets at 45° are rarely synonymous with fine tune accuracy.

The system I use is a 3' x 2' target parallel to the sensor with a good general AF detection target in the centre that separately includes detail equivalent to 200 LPM near the centre and in the corners.

Three test shots, one at -3 fine tune, one at nil and one at +3 indicate the direction of any possible fine tune issue.

With this type of target I find the need for fine tune adjustment is extremely rare - with the recent Nikon equipment in good condition.

I always test "just in case" after a lens or a body has had an unintended moderate impact.

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.

 

[monte12345]

Quite likely to the points you made in your post. Yesterday I got out my larger tripod and set up to resume getting that lens tuned properly. The subject I used is quite prominent to the pics of that Robin in it's nest. I used the brick wall with the Dynamic area and moved to a 12 foot shooting distance in order to tune the focus for a distance that is sort of "normal" for my shooting. It took a bit of time but the settings are now -2 for Wide and Tele is at +3. In an ideal world I'd like the Tele at +3.5 but considering how near to perfect the present settings are a tiny little bit of front focus at the 70mm focal length isn't really enough to fuss over.

 

[Ruedon]

Investing time into lens fine tuning, you might consider getting a dedicated tool. I only did this once with the Sigma 18-35/1.8 on my D500. The built-in feature of the camera didn't work well for me. This is why I did it with trial&error in the lens firmware -- should work well with support for manual focus lenses in Z bodies. If you can do it with lens firmware, then the settings are stored once for all there. Focus on outer image areas at wide angles was most tricky. Bad though that this is needed at all with on sensor AF :-(

 

[Leonard Shepherd]

There are two challenges using this type of target.

The first is that depth of field is not equal both sides of the intended point of focus.

Using where the outer lines away from "O" become unacceptably sharp either side of the intended focus line is not helpful as there is always a wider zone of sharpness behind the intended focus line than in front.

How much difference there is between the width of front and back acceptable sharpness in an image depends on several things including focus distance, focal length, format and aperture – so a bit of a challenge for reliable estimating if the "0" line is not be in the centre of the depth ion field.

Second there is no recognisable subject such as a face for AF detection - so AF has to focus on one of the vertical lines for AF detection

There is no vertical line alongside the "0" line - only cross shapes that AF might get wrong for "central distance" similar to when reading a geometric pattern. This can result in the AF focussing a bit in front or a bit behind where intended :-|

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.

 

[Ruedon]

There are two challenges using this type of target.

...

Second there is no recognisable subject such as a face for AF detection - so AF has to focus on one of the vertical lines for AF detection

There is no vertical line alongside the "0" line - only cross shapes that AF might get wrong for "central distance" similar to when reading a geometric pattern. This can result in the AF focussing a bit in front or a bit behind where intended :-|

I was focusing on the vertical plane left to the ruler

 

[Leonard Shepherd]

I was focusing on the vertical plane left to the ruler

Ideally there should be a vertical edge not interrupted by the horizontal plane exactly level with the "O" mark.

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.

 

[Schrodingers cat]

Investing time into lens fine tuning, you might consider getting a dedicated tool. I only did this once with the Sigma 18-35/1.8 on my D500. The built-in feature of the camera didn't work well for me. This is why I did it with trial&error in the lens firmware -- should work well with support for manual focus lenses in Z bodies. If you can do it with lens firmware, then the settings are stored once for all there. Focus on outer image areas at wide angles was most tricky. Bad though that this is needed at all with on sensor AF :-(

Although there are a variety of AF tuning methods in service, this particular AF fine tune system has been employed, if memory serves, for a bit over a decade. It is one of the time proven methods that provides accurate results for most users, although I would think there will always be outlying cases where it is not effective. Never personally identified one, but I would think it might be out there someplace.

Something I feel is an important feature is that it is immediately obvious, in the very first photograph, in which direction the AF is out.

I've never had occasion to use this device with a mirrorless camera, only DSLR's. I suppose there might be some difference in functionality with different systems but have not seen such a thing reported.

I have noticed that, in my use case, that it's necessary to perform the test more than once. I caused myself some needless difficulties back in the D800 days by conducting testing in an insufficiently rigorous manner and producing misleading results. Repeatability is key.

My experience was that I needed to use a tripod, exposure delay, and bright lighting for the best results. Bright outdoors worked best for me. Although I would think it obvious, there occasionally seems to be confusion in that some think you are focusing on an angled target, which is clearly not the case.

It's also important, and somewhat difficult, to align the device accurately. If I did not have the target parallel to the sensor the results were unsatisfactory. if I did my part, had the alignment correct, and used rigorous technique it was highly effective for me.

As depth of field is not generally equal on both sides of the point of best focus depending on distance and aperture I suggest trying to make it so may be unhelpful unless you have some unique requirement.

I also found, for me, that wide angle lenses were more challenging.

I know nothing about tuning in conjunction with subject detection. Not much about subject detection in general for that matter

I actually prefered another version of this device from a different manufacturer. That version includes provision to use sighting holes in the target to increase ease of achieving correct target/sensor alignment. Sadly, the designer of this second version experienced health issues and I believe it may be discontinued.

It's been my observation over the decades that you can ask 5 photographers the same question and get 6 different answers Af fine tuning methods seemed to be one of the most polarizing, with people being highly defensive of their choice. Except for me of course

--
Personal travel snapshots at https://www.castle-explorers.com
Making good decisions is generally the result of experience. Unfortunately, experience is generally the result of making bad decisions.