[sebberry]

Assuming you're picking suitable AF targets for PDAF, it's definitely not normal for a DSLR. I get very good consistency in AF.S with my K-3II, K-3, K-5, K10D, even my *ist DL, in most normal situations, so long as I choose an AF target wisely...

I was using the back of a box of crackers, focusing on the nutrition guide When it nailed focus, I could clearly see the halftone pattern used by the printing process. Longer shutter or higher ISO to slightly overexpose according to the meter seemed to improve accuracy consistency.

[BigMackCam]

I was using the back of a box of crackers, focusing on the nutrition guide When it nailed focus, I could clearly see the halftone pattern used by the printing process. Longer shutter or higher ISO to slightly overexpose according to the meter seemed to improve accuracy consistency.

Interesting. I've had the same problem when testing AF fine focus on a box of cereal with a couple of DSLRs (see my recent comment on this very matter). My conclusion - though I have no firm basis for this - is that there was something about the printing process that confused PDAF.

I'd encourage you to try a different focus target... just to see if it makes a difference.

[licht96]

Got a reply from Ricoh... Sadly not really understanding the problem, since they assume a back or front focus of the camera, that can be fixed by an additional repair.
I typed so much... I send a PPT with everything explained... I send two additional pics with a 100% hit of the old K3 II and an off Pic from the new, epaining, that the new is totally inconsistent...very hard in outer AF pioints and poor( compared to older Pentax camera) with AF spot... I really typed so much....
... I think the problem is, that different people are involved in the Hotline and answering there...

It's not a Front Focus or a Back Focus! I can handle this in the Menue of the camera....
... but when it's one pic a front focus and the next a back focus... and sometimes totally off, that in theory it wouldn't be possible to adjust it in the menu.
Sorry, that I cry here in the forum... But my wife don't want to hear this anymore ;-)

I wish everyone more luck with their new K3 III.

[sebberry]

Keep fighting the good fight!

[BigMackCam]

Got a reply from Ricoh... Sadly not really understanding the problem, since they assume a back or front focus of the camera, that can be fixed by an additional repair.
I typed so much... I send a PPT with everything explained... I send two additional pics with a 100% hit of the old K3 II and an off Pic from the new, epaining, that the new is totally inconsistent...very hard in outer AF pioints and poor( compared to older Pentax camera) with AF spot... I really typed so much....
... I think the problem is, that different people are involved in the Hotline and answering there...

It's not a Front Focus or a Back Focus! I can handle this in the Menue of the camera....
... but when it's one pic a front focus and the next a back focus... and sometimes totally off, that in theory it wouldn't be possible to adjust it in the menu.
Sorry, that I cry here in the forum... But my wife don't want to hear this anymore ;-)

I wish everyone more luck with their new K3 III.

Just "keep on keeping on". I went through a similar process with Tamron's UK service centre with my 10-24... After replacement with a new lens and a new set of problems, I finally got them to understand what was wrong. I had to send them both my K-3 and lens (which left me feeling very nervous) along with a complete print-out of my lengthy explanation, and request for them to test specific things... but they eventually "got it", and the lens was successfully aligned, tested and returned with my camera.

Good luck and keep us informed!

[c.a.m]

To @licht96 and other interested parties, I'm late to the game with this post (I needed to find some time to do a proper test).

I tested one of my lenses, FA 43mm Limited, for its AF performance on my K-3 Mark III. My set up and procedure was similar to what I described in a recent article: K-3 Mark III and Firmware 1.31: Requires New Autofocus Fine Adjustment - PentaxForums.com

In summary, here is my setup, following the OP's list:

Pentax K-3 Mark III, Firmware 1.31
Lens SMC Pentax FA 43mm Limited
Focal length 43 mm
Aperture f/2.8, f/1.9
ISO 125-200
Exposure Time 1/200, 1/400 s
Camera tripod mounted; SR Off
White Balance AWB
Focus Adjustment to center: 0 nominal (set to +6 in one test)
Lights: 2 compact fluorescent bulbs, 23 W, 6500 K, mounted in 20-cm workshop reflectors, 60 cm from target centre, offset 40 degrees left and right from the target axis.
Ambient temperature: 18° C
Distance Focal plane camera to Focus Test target: 200 cm
Camera horizontal and vertical adjusted with internal balance
Target level and aligned with sensor plane
Before each shot the lens was defocused to infinity.

AF mode: AF.S, SEL S (Select single point), single shot.


Here is a picture of the target setup, as seen in my basement workshop (actual test shot 5981, referenced below):

The next figure shows the map of the camera's AF points superimposed on the target within the test scene. For reference, the target has a width of 46 cm. The distance between the camera's sensor plane and target is 200 cm.

In summary, the seven points within the central AF frame that I tested all provided a sharp focus at the baseline optimal AF Fine Adjustment (AFFA) setting of zero. The points on the periphery (3,5,6,9,10, 13) all produced mis-focused shots when using the optimal AFFA setting of zero.

My original baseline AF Fine Adjustment test, performed earlier when I updated to Firmware 1.31 and using the standard central AF point, is shown in the following figure, top graph. The AF consistency was very good and the overall data was tight. The 'Relative Focus Quality' indicates the variation of focus sharpness as the AFFA setting is changed. The optimal AFFA setting is zero for this lens. Note that any image with an RFQ above 8.5 is considered well-focused; there is no apparent difference in image sharpness when viewing at 100% full-scale on an HD 1920 x 1200 24-inch monitor. See the referenced paper above for more details.

The lower graph shows how the optimal AFFA setting changed when using the far left edge AF point (Point 3 on the map), positioned over the centre of the black target cross. The optimal AFFA setting is +6. The lower graph also shows (Run 9) that the centre left AF point (Point 2) provides a sharp focus at AFFA=0, with an AFFA profile that is practically identical to the baseline case.

The next graph shows the focus consistency for two cases. In Run 10 with AFFA=0 and aperture f/2.8, the camera and lens 'nailed' every shot in the 10-shot series. Run 11 shows the shot-to-shot consistency wide open at aperture f/1.9. In this case, the AF precision is also very good. However, the purple fringing and generally softer optical characteristic that the lens produces at f/1.9, lowers the relative image quality compared to the f/2.8 case, which is seen here as a lower RFQ value. Despite the purple fringing, the camera and lens nailed the shots with respect to the focus.

The main part of this test examined the AF results for 13 different AF points, as indicated in the AF-point map above. The results are shown in the following graph. The non-central AF points (3,5,6,9,10,13) resulted in images that were seriously out of focus.

To test the AF of the non-centre points and obtain images for comparison, the camera was moved on its ball head mount and secured to place the point at the centre of the black cross on the target. The lens was manually defocused and then focused using the back AF button; the camera was repositioned again to place the centre of the frame back to the target's centre; then the shot was taken. In this manner, the peripheral AF point was used to focus, while the centre of the target was used to determine the relative focus quality. This avoided any potential degradation of the lens' sharpness towards its edge. With a target distance of 200 cm, a target half-width of 23 cm, and depth of field of 23 cm at f/2.8, any geometrical focusing error introduced by this 'focus and recompose' method should be negligible (as evidenced in Run 15, last graph below).

Finally, in the following graph we compare the focus results when using the left edge AF point (number 3) at two different AFFA settings. At AFFA=0 (Run 14), the relative focus quality is poor, as described above. Resetting the AFFA to +6 results in very good, consistent focus (Run 15). Shot 1 is the reference data from image 5981, which used AF Point 1 (same as AF Point Number 1 in the graph immediately above). Shots 2-6 used AF Point 3 for each of the AFFA sets.

My test led me to conclude that for my FA 43mm Limited lens, the outer AF points beyond the central frame require a different AFFA setting than those inside the frame.

To explore a possible variation in focus accuracy between the central cross-shaped AF sensors and the peripheral line-sensors, I ran several other tests using different sections of the focus target. For example, the AF point was placed just to left of the centre of the black cross to ensure that the horizontal line was within the line-sensor's field. I found no difference in AF performance.

Owing to time limits, I did not test all of the peripheral points to the same level of detail. However, it is believed that the selection of the 13 dispersed points was adequate to provide a reasonable input to the issue raised by the OP in this thread.

I prepared this post somewhat quickly, so I may have left out some details or missed an explanation or two. I'd be glad to receive any comments or questions on the test procedure or results, general observations, or suggestions for improvements.

- Craig

Is this why the the AF Area Restriction option excists?

[licht96]

Wow. What a detailed analysis.
I feel a little guilty that you spend so much time after my request, to check the AF points... I didn't expect such effort like you did!
I think I've to read it twice or three times to fully understand your charts, xls and graphs.
But from the first time I take some interesting things: the different AF settings from the inner and outer zone... That should be implemented in the camera... May be different for each lens. Or even Aperture? But that should be nothing new to an expert team, that invented the AF system and/or the algorithm...

The second thing: nice to think about some specific targets, for the different AF fields (cross and line).
I wonder wich are the right one in comparison to my focus target...
OK. Give us some time to take a look at ok at your deep analysis... especially after some beer yesterday ;-)

But also good to see, that accuracy is much better than in my copy.

And to the comment of Tjompen: I would understand this result in the same way: for some lenses, there are restricted areas due to the fact, that Pentax discovered totally inaccurate focus... And for other lenses they thought, it could be acceptable (and in this case it seems, it isn't really acceptable... Hmm).

[PentaFOx]

Hello everybody,

I am a little late to this show. Wanted already to post earlier.

I have a K3 III and the new HD DA* 16-50 mm PLM combo and only have practical experiences about this topic. So no standardized lab tests.

Unfortunately I can confirm licht96's observations. Using non-center AF points appear to deliver uneven results (not only the extreme outer AF points). Mostly pretty off. The center AF-point on the other hand delivers in the same situation very good to excellent results. Yes, I know, shooting free handed is nothing which can be measured nor properly reproduced – but this is what I am doing most of the time and I must admit that I hardly can rely on the non-center AF points (no matter if inner or outer). I actually wanted to work more with selecting AF points. The new comfortable stick is a great feature which should be used as intended – but without reliable focussing apart from the center AF-point I pittily rather would avoid using it.

I know this is a pretty subjective observation but I really would appriciate – and I believe it is licht96's wish as well – that people who own a K3 III and especially a HD DA* 16-50 mm PLM share here their experiences/observations using non-center AF-points.

Many thanks in advance.

[gatorguy]

Hello everybody,

I am a little late to this show. Wanted already to post earlier.

I have a K3 III and the new HD DA* 16-50 mm PLM combo and only have practical experiences about this topic. So no standardized lab tests. I have no

Unfortunately I can confirm licht96's observations. Using non-center AF points appear to deliver uneven results (not only the extreme outer AF points). Mostly pretty off. The center AF-point on the other hand delivers in the same situation very good to excellent results. Yes, I know, shooting free handed is nothing which can be measured nor properly reproduced – but this is what I am doing most of the time and I must admit that I hardly can rely on the non-center AF points (no matter if inner or outer). I actually wanted to work more with selecting AF points. The new comfortable stick is a great feature which should be used as intended – but without reliable focussing apart from the center AF-point I pittily rather would avoid using it.

I know this is a pretty subjective observation but I really would appriciate – and I believe it is licht96's wish as well – that people who own a K3 III and especially a HD DA* 16-50 mm PLM share here their experiences/observations using non-center AF-points.

Many thanks in advance.

Of the 101 total focus points only 41 are intended to be user-selectable for AF and that's according to Pentax. Even then it's dependent on the lens. It comes as no surprise that the ones on the periphery are less reliable. FWIW I still use focus recompose and avoid trying to focus to anything on the edge of a frame, and TBH I can't think of a situation where I would want to. Anything in the center should be accurate tho. Are you having issues with the center area and selectable AF?

EDIT, quoting Pentax in case I've misunderstood:
SAFOX 13 AF system with 101 focus points
The number of focus points in the PENTAX K-3 Mark III have been increased to 101, from 27 in the PENTAX K-3 II. The AF area also has been greatly expanded. Of 41 user-selectable points,* 25 are cross-type sensors. This high-density AF system enhances the flexibility of image composition, while optimizing focusing accuracy on the subject. Since its middle focus point is designed to detect an F2.8 luminance flux, the camera assures super-high-precision focusing when using a bright lens with an open aperture of F2.8 or larger.

*The number of selectable points may vary depending on the mounted lens.

[PentaFOx]

Are you having issues with the center area and selectable AF?

Thanks gator,

I actually would not use the AF points in the periphery as well. I am having issues with the user selectable AF points around the one center AF point – the guys in the bracket. Maybe I was a bit unclear here. As mentioned – I have no problems with the AF point in the perfect center.

Why would one not use all focus points if available? That makes no sense.

[sebberry]

Thanks gator,

I actually would not use the AF points in the periphery as well. I am having issues with the user selectable AF points around the one center AF point – the guys in the bracket. Maybe I was a bit unclear here. As mentioned – I have no problems with the AF point in the perfect center.

This mirrors my experience. Center point AF is fine (most of the time). Just one or more spots off-center and the AF is off. I haven't yet had the chance to burn up some shutter actuations to test whether these points are front or back focusing with any sort of consistency.

---------- Post added 01-03-22 at 09:23 PM ----------

Why would one not use all focus points if available? That makes no sense.

Exactly, especially any sort of auto AF and/or with tracking. You need those additional points to be just as accurate as the center/spot AF.

[licht96]

Hm..now the question still remains: what are this amount of AF points for? And the AF stick as well, when I can´t rely on them?

But honestly: I can´t believe that.
The response from the forum is very limited and it would mean that all the commercial things are not true.
Furthermore all the happy forum users using this new fancy functions can´t be wrong. As mentioned by sebberry: this Points are also used by the tracking and AUTO functions. So all the nice “Bird in flight” pictures wouldn’t really possible.

When our Forum Youtube Star Kobie ( ;-) ) received his 16-50 PLM I asked him immediately on YT for this topic. He was so kind remembering this thread and tested it and reply that he sees no issue.
Furthermore he (and a lot of other people) are using the new Auto functions – as Face or Eye AF through the OVF….and they are happy about their results…hopefully…otherwise I would expect more feedback here.

I must admit I tried it sometimes…. but I didn´t worked for me as I expected something more reliable.
The AF points moved on the face…sometimes hitting an eye…ore both…but sometimes the cheek as well…but: when I check the focus area with Ok (or looked afterwards at the computer screen) the red dots clearly showed “a” hit…but it was totally out of focus!
So that started my investigations…and ended up with my conclusion that I´ve a bad copy that is out of tolerance. That is proofed by identifying that the Spot AF as well is not as reliable than in my older K3 II….

So – coming back to others copies of the camera in the forum - I can´t believe that this is state of the technology. Yes there are limitation of this kind of AF…but if they are in that way, that the hit rate goes down immediately using outer AF points….than the Phase AF has really NO chance to survive.***
And it must be capable at wide open as well….in my understanding….when we are talking about portraits….and eye AF….and expensive fast lenses ….what are they for when not using it @ < f 2.8? I don´t take a portrait @ f8 when I want to separate it from the background…
And yes: as mentioned here before: I´m also used to the Center AF with recompose! I did this my entire photo life. But I was looking forward to do other things with the new model of Pentax.

I still believe that there is something wrong with my copy

***and the two days I´ve the D500 with quite bigger AF field, I´ve no recall that I face this kind of problem. That argue against the assumption that the DSLR AF is not capable…

[PentaFOx]

Hello everyone,

tried a bit more methodical testing. Please don't laugh at me. I know it is still not close to a professional lab test – but I am afraid to tell that it maybe confirms my fears.

Setup:

• K3 III on a tripod
• f/8, 0.6s, ISO 160
• tested with both lenses: SMC Pentax-DA 50 mm and HD Pentax DA* 16-50 mm for comparison
• target ... well Siemens stars are maybe a bit outdated, but I had no better target in reach – I think it is ok tho

Each of the red highlighted focus points were tested. After that I composed each image (crops of each area) to one image.
Please note that the printed target is indeed pretty pixelated. So recognizing the pixels of the graphic elements on the images is acutally a good hint for a good focus.

Please refer the full size images (links beneath the lowres previews).

Please consider this is the actual examined area:








At first I run the test with the SMC Pentax-DA 50 mm. For my taste it basically hit almost always the correct focus:




Full size: http://www.foxonatrampoline.eu/pics/pentax/SMC-Pentax-DA-50-mm.jpg



Then I tested the HD Pentax DA* 16-50 mm. It seems the user selectable non-center AF points had problems to find the correct focus.
The center AF point had no problems at all and delivered almost always the correct focus. Using lower f/-numbers show the misfocussing even more clear.



Full size: http://www.foxonatrampoline.eu/pics/pentax/HD-Pentax-DAstar-16-50-mm.jpg



Of course still no professional test but the conclusion seems that there might be at least an issue with the K3 III and the HD Pentax DA* 16-50 mm.

Do think this is possible? What might be the reason?


Cheers.