Reikan Focal info on Z Series AF-Fine Tune and Latest Firmware Release - Update 9/29 - Z6 Firmware Update

[MartyD]

I thought this was interesting related to the Z series AF-Fine Tune

Nikon Z6, Z7, Z50 AF Fine-Tune Firmware Changes - Reikan FoCal

Nikon's latest firmware for Z7, Z6, Z5, Z50 changes AF Fine-Tune operation for Z-mount lenses - learn more in our post here.

blog.reikanfocal.com

Since the most recent firmware update, saved AF-Fine Tune values for Z series lenses do not apply. They can be stored in the camera but will not be applied when shooting. If the AF-Fine Tune needs to be adjusted it needs to be put in the Default value setting. This also causes problems when using FoCal software to AF-Fine Tune Z lenses.

AF-Fine Tune with F series lenses and the FTZ adapter works as expected.

It is not known if this is a firmware bug of if Nikon feels the Z lenses don't need any AF-Fine Tune and Nikon has not commented on the issue.

Update 9/29 - Firmware update 3.11 released for the Z6 today related to battery issues but Nikon identifies the AF-Fine Tune issue and states that it will be addressed.

Nikon | Download center | Z 6 Firmware

 

[Pistnbroke]

It would be useful if steve could comment on why we need FFA at all if the focus is on the sensor.
This would seem to me would also apply to F mount on the FTZ adaptor as it too gets its focus information from the sensor /

 

[Pistnbroke]

I don't agree FFA is a waste of time.. I have two 28-300 Nikons . one needs +2 the other +15. And don't talk about Tamron 100-400 on the tap in . One is all negative from -4 to -11 and the other all positive with a similarly wide range ..great lens ,light and cheap

 

[Pistnbroke]

Does more harm than good = waste of time

Today I do it on the D850 auto FFA at 300mm which is the weakest part of the lens so needs the most help . This is my wedding lens and I always shoot at F8. I also check on the D850 then fit the lens to any of my other Nikons FX and DX and always found the setting correct when tested. I take it that the variance is in the lens rather than the mount to sensor/focus module. I also obtain all the offsets for the Tamron console from the D850 then input them to the lens via the console

 

[Pistnbroke]

Wrong reasons?
Any new lens I get I check the focus adjust ..almost all need some ..is that a wrong reason.?

 

[Steve]

It would be useful if steve could comment on why we need FFA at all if the focus is on the sensor.
This would seem to me would also apply to F mount on the FTZ adaptor as it too gets its focus information from the sensor /

Basically, because there's no CDAF trim after PDAF operation. I have a longer explanation in my Mirrorless AF book (although, unless you're familiar with PDAF and CDAF, you probably need the info that preceded this in the chapter)

At this point, you may be curious exactly how any of this front or back focus buffoonery can occur, since you’re literally focusing right off the sensor.

Well, think of it this way. Imagine if our lens focused in “points” on a scale of 1-100. It doesn’t, but just indulge me for a moment .

Further, we’ll say “1” is minimum focus distance and “100” is when the lens is at infinity. Every other place lands in-between. With me?

Let’s say you focus on a subject mid-way between the two. The PDAF system looks at the difference in phase discrepancy and decides the focus ring needs to go to “50” for proper focus. It sends this to the lens and the lens moves to the “50” spot.

So far, so good. But what happens when the tolerances with the lens, mount, or adapter (if you’re using one) are off?

Well, the camera would still send the value of “50” to the lens, but because of a variation in component tolerances, your particular system really needs “52”. However, unless you’ve fine-tuned the lens, the camera doesn’t know this. So it uses the value of “50” and front focuses.

Of course, you may be wondering why the camera doesn’t just see that it’s still not as sharp as possible when the lens focuses to “50” and makes a correction.
The thing is, unlike CDAF, PDAF doesn’t “massage” the focus like that - it would take too long. It merely looks at the phase difference and tells the lens how far to spin the focus ring.

A very basic explanation of what happens goes like this:

If the image is still out of phase after the camera sends the value of “50”, the camera assumes that’s as sharp as it can get under the circumstances. After all, every time the camera checks the phase difference, it comes to the same value for the distance, 50 points. If the lens is focused at that distance, the camera assumes it’s as close to perfectly focused as possible.

The reason we can’t get the camera to focus to the value of “52” required by our out-of-tolerance setup is simple. The camera assumes the tolerances are correct. When they’re not, the camera will make the same “mistake” over and over.

It’s like if you had a ruler that wasn’t quite right. Say you were supposed to cut a few boards to 6” long but your ruler really measured more like 7” instead. You think you’re cutting 6” boards, but when you give them to someone expecting 6” boards, it turns out they are too long because the ruler wasn’t in spec. If that same person asks you to cut the boards again without telling you the issue, you will make the same mistake again since you’re unaware of the problem.

Now, if someone told you that your ruler was 7” and not 6” you could correct for the error - and that’s what AF Fine Tuning does. It lets the camera know that the “ruler” is a bit off and allows for a correction.