[StigVidar]

if you have any Flat-headed screwdriver, you can rotate AF screw using that. (becareful!)
and you must look at focus-distance-mark, remember whether it was moved or not.
if lens focus hasn't be moved immediately although you have already rotated AF screw, this lens has an back-lash problem!"

But this "Back-lash" is something all screwdrive lenses have, more or less, and the algorithms for focusing can handle it. The focusing process is a closed loop where the camera is constantly checking for correct focus. You have probably heard it when the camera do some final smal focus adjustments at the end.

[redpit]

But this "Back-lash" is something all screwdrive lenses have, more or less, and the algorithms for focusing can handle it. The focusing process is a closed loop where the camera is constantly checking for correct focus. You have probably heard it when the camera do some final smal focus adjustments at the end.

Of course, the problem is with microadjustments and whether the AF module can actually stop a screw driven lens exactly where a lens with electromagnetic AF can be set. If there is a "play" before the lens elements actually move those microadjustments might not be possible to achieve focus exactly where the AF module aims.


Anyway this is something that seems very rational to me and it comes from a person with inside knowledge. Moreover it is really true as the KAF4 lenses work like a charm. If there were problems with these lenses we would talk differently.

[Mccsiz]

I like how you've presented the images. Very easy to see the various focus planes and their sequence. And it appears that the scene was uniformly illuminated, which is critical for this type of test.

It's possible that the AF point is covering more than a single battery in each shot -- the AF points are not really points per se; they cover a larger area than they appear in the viewfinder. If this is the case, the AF system may have settled on a random battery in each shot, rather than on the one you think you focused on. On my K-3 Mark III, the centre AF Spot 'point' actually covers more than half of the central circle as seen in the viewfinder.

Here's a brilliant method to check the coverage of an AF point: How to check your AF "point" coverage / sizes - PentaxForums.com

It's not obvious that the line of battery cells presents an unambiguous target to the AF detection system.

It would be useful to know the distance from your camera to the batteries.

If you could post an image of the full scene (not cropped, but compressed to save space here), that could give us an idea of the relative geometry between the focus point and the subject scene.

Also, what AF point was used? Spot, SEL (S) single point, etc?

- Craig

Excellent reply. Thank you CAM.

Cheers,
Loyd

[Mccsiz]

I just loaded V1.31 onto an SD card and attempted a downgrade, and the camera displayed 'Upgrading v 1.41 --> v 1.31'...so maybe you can downgrade.
I didn't go through with it...still cogitating on whether I should do it.

Cheers,
Terry

Don't risk it. You'll be sad. Wait for the next upgrade.

Cheers,
Loyd

[Mccsiz]

Are you NOT aware that you are pairing a modern electronic AF digital camera to an obsolete mechanical screw-drive film-era lens introduced in 1991 AND expecting consistent razor sharp results?

Given all the uncontrolled variables in play, you got what I would expect.

So, what's your point?

Just curious... M

I think he said that the lens worked well with previous versions of the firmware.

Cheers,
Loyd

[tduell]

Don't risk it. You'll be sad. Wait for the next upgrade.

Cheers,
Loyd

Thanks, I didn't.
Already discussed.
Given that there is a warning, albeit in fine print, which is not the way to get attention, I'd have thought it would be smart to have the camera refuse to install an earlier version.

Cheers,
Terry