[agukha]

Here is a method that could be used to do a fast calibration, I believe.

Let's start with the heart of the method, sophistications could be added afterwards :
The camera would be set to use center point AF, the target (for example a focus adjustment tool alignment ruler folding card) must be perfectly centered on the AF point by the user, at the distance he wants to make the calibration more precise for his photoshoot.

Then we can launch the processus, the camera would make automatic focus (at the maximum aperture), remember the focus adjustment value, then switch to liveview and do the same logic, comparing the 2 values, adjusting the lens calibration new value, test it again, until the difference is the minimum the calibration can do, and save it for this lens.

The sophistications to consider could be to set the focus at minimum and or maximum before doing the focus, or to choose another point than the central one, use the calibration only for the current shooting without saving it, etc etc.


I wanted to code it using the Pentax API, but it is pretty limited, we don't have access to almost all functions needed here.

[Mooncatt]

So basically a script that automates the dot tune method. That could be useful.

[aaacb]

Nikon has done this some while ago Maximum sharpness: Nikon's automated AF Fine Tune explained: Digital Photography Review

[biz-engineer]

Nikon uses contrast detect AF as reference to calibrate PDAF. Problem is, on my Pentax K1 and K1 II, PDAF is more accurate than CDAF, and I don't know why, but it is more accurate. If I'd tune AF based on CDAF, my camera would be less accurate than it is with factory defaults. So maybe Nikon have implemented AF fine tuning in camera because that saves them the cost of calibrating their DSLR on the factory line, letting customers calibrate the cameras with their lenses at home.

[Medex]

Nikon uses contrast detect AF as reference to calibrate PDAF. Problem is, on my Pentax K1 and K1 II, PDAF is more accurate than CDAF, and I don't know why, but it is more accurate. If I'd tune AF based on CDAF, my camera would be less accurate than it is with factory defaults. So maybe Nikon have implemented AF fine tuning in camera because that saves them the cost of calibrating their DSLR on the factory line, letting customers calibrate the cameras with their lenses at home.

Do you mean LiveView Autofocus on your k1 is missing focus more than optical viewfinder autofocus?

[Jonathan Mac]

I'm pretty sure some of the more recent Nikon DSLRs do exactly this. It's something that should be easy to implement and should have been added since the dawn on live-view focusing.

[shyrsio]

Hey Pentax (Ricoh), are you reading this?

[gatorguy]

I'm pretty sure some of the more recent Nikon DSLRs do exactly this. It's something that should be easy to implement and should have been added since the dawn on live-view focusing.

How does Canon's version work, same as Nikon's?

EDIT: No, apparently Canon handles it the same as Pentax.

As an observation I had three lenses I had to fine-tune with my K3III even tho they required no adjustment on any of my other Pentax cameras. Since the latest firmware though two of those are now best back at the default "0". I haven't checked the third one yet. From personal experience my good Pentax glass generally needs no adjustment whatsoever, whether on a cheap K-70, or used on my full-frame K1. Perhaps Nikon isn't as careful with initial lens adjustment and thus leans more heavily on the lens owner making the adjustments for them?

Anyway, anything that simplifies the need when it arises is of course appreciated. I do have some lenses that have needed it over the years, while some others really don't matter.

[biz-engineer]

Do you mean LiveView Autofocus on your k1 is missing focus more than optical viewfinder autofocus?

My liveview AF isn't missing focus, but it doesn't give the sharpest possible pixel, PDAF slight better, possibly because there is a small final tweak step at the end of the PDAF sequence (AF.S mode).

[agukha]

Another solution would be that Pentax add all the needed functions on the API ! ^^

[stevebrot]

My understanding is that the Nikon system uses bracketed flat-target image data directly for its in-camera auto-PDAF calibration. As such, there is no need for provisions other than a vertical black/white boundary flat target and a tripod.

See D500 user manual, pages 310 and following.


Steve

[zapp]

Doing AF fine adjustment automatically would be nice, but there is much more to it than finding focus on a target. There is still a lot of possible user error involved in the described setup. Best focus… well, what does that mean? A decent workflow also considers DOF positioning. A target is required for alignment. This will not ship for free with the camera. How to optimize zoom lens performance. Pentax already compensates internally for distance and aperture offsets.

[agukha]

Doing AF fine adjustment automatically would be nice, but there is much more to it than finding focus on a target. There is still a lot of possible user error involved in the described setup. Best focus… well, what does that mean? A decent workflow also considers DOF positioning. A target is required for alignment. This will not ship for free with the camera. How to optimize zoom lens performance. Pentax already compensates internally for distance and aperture offsets.

Of course but it is the same when you do manually an AF adjustment, except with this option you wouldn't need to to check yourself each time where the focus is, if you must add or remove distance on the setting, etc. On both cases you need to choose the distance you want and put a target, this is not the harder part.
The usb dock for the Sigma lenses is doing more, but it is possible because of the firmware in their lenses.

(by the way, I have exposed the basic schema for a semi automatic AF tuning, but it could have modes where it measures the focus at different positions of the zoom (yes, the user would need to zoom in and out at some time ) and then it could choose an average tuning possibly less precise on a specific distance but better overall, juste a choice depending on what you prefer to do.)

If you want something working always in any cases and without user actions, then there are smartphones

[zapp]

Pentax needs no dock, they make the camera, the lenses and the firmware. Who is Sigma?
Your basic schema raises more questions than answers.
Some things you need to just do and not wait for “it” to do it for you.

[Ian Stuart Forsyth]

Pentax needs no dock, they make the camera, the lenses and the firmware.

None of the Pentax lenses that I have tested for AF where profile close enough that I could use the same AF correct over the entire zoom range, or subject distances or now much I stopped down the lens

This includes the DA 300 4, 50-200, DFA 100 2.8, DA 55 1.3, DA* 16-50, 18-55, DA* 59-135 2.8, DA 21 2.3, DA 12-24 and DA 55-300