[jrsliwinski]

Hello:

I just picked up a DFA 24-70mm to use for landscapes with my K1mkII. All of my other wide angles are A and M lenses and my eyes sometimes mis-focus, so I wanted something with auto-focus.


Straight out of the box, I noticed that regardless of the zoom setting or aperture, the lens of not focusing correctly using PDAF. It appears to have a really bad back focusing tendency. CDAF works spot on EVERY time - photos are very sharp.

I attached the same lens to my less than 1 year old K3 mk III and PDAF works perfectly, regardless of zoom setting or aperture. CDAF is fine too.


I attempted to adjust the AF fine setting on the K1 with the 24-70 attached and hit +10, but it is still back focusing quite a bit.

I tested my K1 with some other lens, notably my DFA 100mm f2.8 Macro and no focusing issues with it.

Is returning the lens the right course to take, is it time to send the K1 to be service (purchase May 2018) or something else?

Thanks!

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Last edited by jrsliwinski; 02-05-2023 at 07:54 PM.

[Ski Jumper]

Following. I'm at a -10 on my da 300 also.

[pschlute]

I would suggest first doing some AF tests making the lens autofocus a number of times from the closest focus distance, and then from infinity. See if you get any difference in results.

It is unusual for a single lens to require such an adjustment, where it is the lens only that is at fault, rather than lens plus AF sensor registration distance.

If you can take the camera to a stockist and try another 24-70 leens

[biz-engineer]

Is returning the lens the right course to take, is it time to send the K1 to be service (purchase May 2018) or something else?

More and more (at least what I can see here), the most expert decision and the best service is when we decide and service ourselves.

[jrsliwinski]

I would suggest first doing some AF tests making the lens autofocus a number of times from the closest focus distance, and then from infinity. See if you get any difference in results.

I did a couple of those. I'd focus at a distance, refocus on my test point, take a shot... Repeat. I don't know if I tried all the way at infinity, so I'll try a few again. Thanks for the suggestion.

If you can take the camera to a stockist and try another 24-70 leens

Already have a second 24-70 on the way.

[shyrsio]

I had a similar problem with my copy and my K1. I bought it used from a seller who was really eager to sell it. When I tried it I understood why. I have now +8 on the focus correction and the lems performs fine. I can imagine why tha AF module could be somewhat thrown off by such a big glass at 2.8. my advice would be try and do some tweaking on the focus correction and don't use targets too far away as it wont be very accurate.
This one is a bit hard to love, but its a lovely lens.

[jrsliwinski]

Second lens arrived. Exact same issue... +10, out of focus, but improving as the aperture is stepped down.

Put that lens on the K3mkIII, wide open, focus is spot on and the image is sharp.

Any additional guidance?

[clackers]

Second lens arrived. Exact same issue... +10, out of focus, but improving as the aperture is stepped down.

Put that lens on the K3mkIII, wide open, focus is spot on and the image is sharp.

Any additional guidance?

Yeah, you've confirmed your camera needs to be adjusted at a service centre.

+/- 10 is as far as we can go by microadjustment, your AF module is actually misaligned and needs to be taken out and refitted or even replaced.

[pschlute]

Any additional guidance?

As clackers has said that sounds like a classic case of AF sensor realignment needed.

However, you said earlier that your 100mm macro lens focusses perfectly !

Can you share some test shots using a focus test chart.

[mikesbike]

I tested my K1 with some other lens, notably my DFA 100mm f2.8 Macro and no focusing issues with it.

This 100mm prime lens operates with the camera's standard old screw-driven technology. It would seem the problem lies in the relationship between the camera's AF system as it connects with the AF motor of the lens. Since the lens works fine on the K-3 III, and another copy of the lens has the same problem on the K-1 II, this strongly suggests there is some problem in the camera's AF operation when it comes to at least some lens's AF motor. There has to be some abnormality here with this particular camera, as this lens was made to be used with the K-1, and has had very little negative feedback, only praise.

[jrsliwinski]

UPDATE: Finally had a break in shooting when I could send the body in... Precision identified the issue as an AF sensor alignment problem. Waiting for it to be shipped back.