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04-10-2022, 08:50 AM - 2 Likes   #136
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When I've used the battery method, I always use an odd number of batteries.
Use 5 batteries so there is an actual center focus subject and 2 points of reference for both front and back focus.
Off hand I believe it was 1/3 of the focus in front and 2/3 focus to the rear is what it should be. You can't properly measure that with just 4 batteries. 5, 7, 9 would be more ideal. And as mentioned, you need to have them spaced further apart so the AF point doesn't pick up more than one battery at a time.

04-10-2022, 11:06 PM - 2 Likes   #137
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QuoteOriginally posted by sebberry Quote
One more example:

After the first test at tuning the lens at f/1.4, I stopped down to f/2.0 and noticed it was missing focus again.

Frustrated, I dialed up the correction to +5 for the top row, and -5 for the bottom row here. The position of the photo correlates to the battery I focused on in sequence.

After looking at the RAW files, I added the arrows to approximate where the focus plane ended up being.

Top row @ +5 AF adjustment
#1 Nothing properly in focus
#2 Slight front focus but fairly clear
#3 Focused on the 3rd battery, but focus landed where it should have for #2. Would have been a very usable photo if what was in focus was where I was aiming...
#4 Bit of a front focus

Bottom row @ -5 AF adjustment
#1 Actually in focus
#2 Back-focused, battery 3 ended up sharper than battery 2
#3 Slight back focus on battery 3
#4 Slight back focus on battery 4

So it's all very strange and inconsistent and frustrating. I can't make reliable AF adjustments with this.
I'm sorry to disappoint you but to me your test is not so valid. I had to make an extensive search to find what is most probably the answer to your question and an explanation to your results. Please read this:
AF-C of K-3III is impressive - Page 3 - PentaxForums.com

I also include the part that relates to your tests:

"K-3 Mark3 has very fast AF speed especially more than older camera like my K-1.
but, depend on many lenses, AF speed of that is very different.
if KAF4, that will be ulmost super-speeded. more than Nikon D6 !!! but it is only for Eye-AF by AE tracking. if subject detection is disabled, less than Nikon D6 (because SAFOX13 is less than A.Multi-CAM37K....)
if KAF3, not bad, very fast and good accuracy Eye-AF,too. All Pentaxians will be very glad and satisfied. just not 100% performance of K-3 Mark3.
If KAF2 (for SDM), I don't know because I don't have one. no tested yet. i think it may be good, just not 100% performance of K-3 Mark3.

If KAF1 (means lens doesn't have motor, just camera-AF motor via AF screw), very difficult problem.
Basically, all AF screw has a back-lash problem. except NEW one. this back-lash means damaged AF screw. so, latency is occured when focus position is already changed!!! this means invalid focus.


I know a hint about it. the Back-lask test method:
I think you already know about position of AF screw in KAF Mount.

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!"


04-11-2022, 01:08 AM   #138
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QuoteOriginally posted by redpit Quote
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.
04-11-2022, 01:25 AM - 1 Like   #139
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QuoteOriginally posted by StigVidar Quote
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.

04-11-2022, 04:47 PM - 1 Like   #140
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QuoteOriginally posted by c.a.m Quote
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
04-11-2022, 04:49 PM   #141
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QuoteOriginally posted by tduell Quote
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
04-11-2022, 04:51 PM   #142
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QuoteOriginally posted by Michaelina2 Quote
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

04-11-2022, 08:41 PM   #143
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QuoteOriginally posted by Mccsiz Quote
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
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