[Adam]

I don't think this is true at all and it certainly hasn't been my experience. I tried AF-C with my K200D and K-3 and quickly came to the conclusion that it's useless and stuck with AF-S. AF-S is generally fine for stationary subjects and gave something like a 90% in-focus hit rate in that scenario, while for moving subjects I need to rely on timing and taking several shots to get something with spot-on focus. My experience with AF-S and stationary subjects on three different mirrorless cameras is that they focus correctly, even at wide apertures, 100% of the time.

I believe that continuous AF with screw-drive lenses cannot work properly because they simply aren't capable of making the micro-adjustments needed to compensate for slight movement of a subject's eye. Lenses with built-in motors should solve this but rely on a good AF system in the camera, which newer Pentax models may have.

I was referring to AF-S accuracy, so yes!

Adam
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[Larrymc]

Is my autofocus module defective? I've seen a few people complain about faulty autofocus on their K-3iii.

I spent $2,400+ on mine. I've had offers of about 33% what I paid. At this point in time I would rather blow my K-3iii up with tannerite, video it, and hope the youtube video paid me back the 33% over time. It's not even about the money at this point in time either. My K30 crapped out with the aperture block failure. I still bought a K-5II, K3, and a KP. The sheer disappoint with my K-3iii in on a whole different level.

Did you ever try to clean the AF Module lens? That might have saved you some frustration.

[idontstairs]

Did you ever try to clean the AF Module lens? That might have saved you some frustration.

Why would Pentax send out brand new cameras with dirty auto focus modules? Off to google to see where the auto focus module on my K-3iii is located.

[pschlute]

Why would Pentax send out brand new cameras with dirty auto focus modules?

Well, one would hope that they don't, but anytime that you change a lens there is the risk of getting dust in the box which may find its way onto the AF sensor.

If you are having AF issues I would use a rocket blower on the camera first.... mirror up.

If that is not your issue then perhaps the AF fine adjustment will help. Do some tests on a tripod with a focus chart.

[JPT]

I don't know about Canon or Nikon AF, or whether it makes sense for you to change to a mirrorless system, but I can say that your experience moving from the K-5 II to the K-3 III does not match mine. I went from the K-5 IIs to a K-3 III and the AF is a big improvement in all regards. This is with a mix of screwdrive, DC and PLM lenses - nothing expensive or fancy. In fact, the K-3 III required less AF adjustment than any Pentax I've owned - basically none.

So I can only imagine you have been unlucky and got a bad unit. Or perhaps some kind of mix-up with settings. In any case, I can't imagine a fully functioning K-3 III would have trouble with the kind of photography you describe.

Also, I heard some people had focus calibration issues improve after a firmware update. The current version is 1.60 and 1.70 should be coming in a few weeks.

K-3 III firmware is available here.
Latest PENTAX K-3 Mark III Firmware Update : Software Downloads | RICOH IMAGING

This firmware is now available, so I would suggest trying it to see if it has any positive impact on your problem.

[idontstairs]

Firmware 1.70 was a huge step back for me. The K-3iii went from about 2 in 10 images not having an auto focus point select to 5 in 10 images not having an auto focus point selected. I took 72 shots. About 35 of them the camera didn't select an auto focus point. Tried about half in af.c XS for the new feature and switched to af.c auto area and it had the same results. When the camera did select an auto focus point many were still low and to the bottom which has been a day one issue for me with subjects moving right to left the camera picks a bottom left focal point and with subjects moving left to right the camera selects a bottom right focal point. Usually the ground and NOT the subject of the image. Today's subject was my dog standing in the yard about 5 to 10 feet away and I used a smc FA 31mm limited between F1.8 to F5.6.

af.c XS center point aimed right at the middle of my dog. Pressed the shutter button down. No focal point selected by the camera when reviewing images.


I do not have this problem with my K5-II, K3, KP, Fuji X100V, Fuji XS10, or Nikon Z6. Only with my Pentax K-3iii.

I've never had an issue with my 31mm lens ever. It worked 100% on my KP for years and the K3 before that and the K5-II before that.

[Levus]

Firmware 1.70 was a huge step back for me. The K-3iii went from about 2 in 10 images not having an auto focus point select to 5 in 10 images not having an auto focus point selected. I took 72 shots. About 35 of them the camera didn't select an auto focus point. Tried about half in af.c XS for the new feature and switched to af.c auto area and it had the same results. When the camera did select an auto focus point many were still low and to the bottom which has been a day one issue for me with subjects moving right to left the camera picks a bottom left focal point and with subjects moving left to right the camera selects a bottom right focal point. Usually the ground and NOT the subject of the image. Today's subject was my dog standing in the yard about 5 to 10 feet away and I used a smc FA 31mm limited between F1.8 to F5.6.

af.c XS center point aimed right at the middle of my dog. Pressed the shutter button down. No focal point selected by the camera when reviewing images.


I do not have this problem with my K5-II, K3, KP, Fuji X100V, Fuji XS10, or Nikon Z6. Only with my Pentax K-3iii.

I've never had an issue with my 31mm lens ever. It worked 100% on my KP for years and the K3 before that and the K5-II before that.

It's a very high possibility that you have a defective unit i think.

[Jonathan Mac]

Firmware 1.70 was a huge step back for me. The K-3iii went from about 2 in 10 images not having an auto focus point select to 5 in 10 images not having an auto focus point selected. I took 72 shots. About 35 of them the camera didn't select an auto focus point. Tried about half in af.c XS for the new feature and switched to af.c auto area and it had the same results. When the camera did select an auto focus point many were still low and to the bottom which has been a day one issue for me with subjects moving right to left the camera picks a bottom left focal point and with subjects moving left to right the camera selects a bottom right focal point. Usually the ground and NOT the subject of the image. Today's subject was my dog standing in the yard about 5 to 10 feet away and I used a smc FA 31mm limited between F1.8 to F5.6.

af.c XS center point aimed right at the middle of my dog. Pressed the shutter button down. No focal point selected by the camera when reviewing images.


I do not have this problem with my K5-II, K3, KP, Fuji X100V, Fuji XS10, or Nikon Z6. Only with my Pentax K-3iii.

I've never had an issue with my 31mm lens ever. It worked 100% on my KP for years and the K3 before that and the K5-II before that.

I agree that you have a defective camera. Even the oldest of DSLRs have better AF that this.

[Larrymc]

Firmware 1.70 was a huge step back for me. The K-3iii went from about 2 in 10 images not having an auto focus point select to 5 in 10 images not having an auto focus point selected. I took 72 shots. About 35 of them the camera didn't select an auto focus point. Tried about half in af.c XS for the new feature and switched to af.c auto area and it had the same results. When the camera did select an auto focus point many were still low and to the bottom which has been a day one issue for me with subjects moving right to left the camera picks a bottom left focal point and with subjects moving left to right the camera selects a bottom right focal point. Usually the ground and NOT the subject of the image. Today's subject was my dog standing in the yard about 5 to 10 feet away and I used a smc FA 31mm limited between F1.8 to F5.6.

af.c XS center point aimed right at the middle of my dog. Pressed the shutter button down. No focal point selected by the camera when reviewing images.


I do not have this problem with my K5-II, K3, KP, Fuji X100V, Fuji XS10, or Nikon Z6. Only with my Pentax K-3iii.

I've never had an issue with my 31mm lens ever. It worked 100% on my KP for years and the K3 before that and the K5-II before that.

Well, you have about three things you can do with the camera! 1. Get rid of it. 2. Keep it and do nothing and keep on hoping for it to heal by itself which ain't going to happen. 3. Send it back for replacement or repair before it is out of warranty. Your choice, I know what i would do. The camera obviously has some problems that are not normal for the K-3 Mk III

[c.a.m]

About 35 of them the camera didn't select an auto focus point. Tried about half in af.c XS for the new feature and switched to af.c auto area and it had the same results. When the camera did select an auto focus point many were still low and to the bottom which has been a day one issue for me with subjects moving right to left the camera picks a bottom left focal point and with subjects moving left to right the camera selects a bottom right focal point. Usually the ground and NOT the subject of the image.

@idontstairs, I think you received your K-3 Mark III in 2021 (I recall some of your earlier dissatisfaction with the camera). Unfortunately, the camera hasn't performed to expectations and you've recounted some odd camera/lens behaviors that don't seem common amongst other users' K-3 Mark III copies. I haven't experienced any of these issues with my own K-3 III.

It's not clear whether you're looking for assistance to resolve the problem(s). However, in addition to the possibility that your camera is simply defective and should be serviced, may I offer several ideas that pertain to autofocus?

• It's crucial to follow a meticulous calibration procedure to set the optimal AF Fine Adjustments for each lens.
• Appropriate AF modes should be chosen for different subjects or situations. Auto Area or Zone Select is not the right choice for many types of subjects or in busy scenes.
• If back-button focus is used instead of shutter-button half-press, the camera will register the active AF point(s) for later review only if the AF button is pressed when the shot is taken. If the AF button had not been pressed, there will be no indication in the review screen of the AF point that the camera used for the shot.

Did you happen to inspect or clean the AF module lens?

- Craig

[K2 to K50]

Firmware 1.70 was a huge step back for me. The K-3iii went from about 2 in 10 images not having an auto focus point select to 5 in 10 images not having an auto focus point selected. I took 72 shots. About 35 of them the camera didn't select an auto focus point. Tried about half in af.c XS for the new feature and switched to af.c auto area and it had the same results. When the camera did select an auto focus point many were still low and to the bottom which has been a day one issue for me with subjects moving right to left the camera picks a bottom left focal point and with subjects moving left to right the camera selects a bottom right focal point. Usually the ground and NOT the subject of the image. Today's subject was my dog standing in the yard about 5 to 10 feet away and I used a smc FA 31mm limited between F1.8 to F5.6.

af.c XS center point aimed right at the middle of my dog. Pressed the shutter button down. No focal point selected by the camera when reviewing images.

Is there any chance you have (with either thumb, or even nose) inadvertently moved the focus point by pushing the K3 joystick knob? I was totally flummoxed by how out of focus some of my shots were at one time until I looked more closely through the viewfinder and noticed the focus point was not in the centre of the frame (where I thought it was?). Or sometimes I have deliberately moved the focus point off-centre for better framing of one shot, then forgot to move it back!!

Also, for a non-moving standing subject I would use AF S, not AF C, as in the case of your dog. If you focus, and then re-frame before pressing the shutter button down full, in AF C your camera might adjust the focus.

I would be very wary of AFC Auto area.

Here is an interesting discussion:

AF.C Auto weirdness when using back-button AF? - Page 2 - PentaxForums.com

Also, of course, Kobie's definitive (?) discussion:
https://www.pentaxforums.com/forums/210-pentax-k-3-iii/440378-ins-outs-k-3-i...standings.html

[gatorguy]

You don't want a modern DFA* like the 50mm F1.4 for sure if you are having autofocus problems.

For the portraits he's interested in I would say the DFA*50 is perhaps a bit too sharp if anything, but AF for portraits is a total non-issue in my experience.

Like Uncle Vanya says, I'm sorry you're having a lesser experience with yours but it's certainly not typical for AF problems with the K3III and DFA* lenses.

[UncleVanya]

• If back-button focus is used instead of shutter-button half-press, the camera will register the active AF point(s) for later review only if the AF button is pressed when the shot is taken. If the AF button had not been pressed, there will be no indication in the review screen of the AF point that the camera used for the shot.

What an awful implementation nightmare. I hate that - I would hope they might fix that in future firmware.

[Larrymc]

What an awful implementation nightmare. I hate that - I would hope they might fix that in future firmware.

Why is it a night mare, if you then move the camera after focusing then what you originally focused on is not in focus. The K-3 Mk I was the same implementation over eight years ago, if you focus and release the AF (back button) the focus point was not registered in the EXIF data Maker Notes for that particular shot. That used to puzzle me until I discovered that I needed to keep the button depressed until the shot was taken. The K-3 Mk I had a rudimentary implementation and would tell you where the focus point was but it only showed in the Maker Notes using the EXIF tool app.

[UncleVanya]

Why is it a night mare, if you then move the camera after focusing then what you originally focused on is not in focus. The K-3 Mk I was the same implementation over eight years ago, if you focus and release the AF (back button) the focus point was not registered in the EXIF data Maker Notes for that particular shot. That used to puzzle me until I discovered that I needed to keep the button depressed until the shot was taken. The K-3 Mk I had a rudimentary implementation and would tell you where the focus point was but it only showed in the Maker Notes using the EXIF tool app.

I didn’t use back button af on my k-3 so I didn’t know it worked that way. It seems so simple to implement a model where if af is used it records into a register the af point then writes that to the file later.