[sbc]

I have a K-3III and DA*60-250. Even with the new improved AF of the camera, focus is still a little inconsistent with PDAF. But LV CDAF is spot on 99%. I guess that is the limitation of PDAF.
On the other hand, I have this DFA 100 macro that is fairly accurate in PDAF but back focus in LV CDAF 100% of the time. I don't know what to make of it.

[zapp]

Are you calibrating with a tripod and tripod mount?
The 70-200 has different AF finetune values for 70/135/200 focal length, but you can typically find working solutions for all focal lengths within dof. The quick release plate on my K1 put pressure on the Phase AF Box. Finetuning results were very consistent with the plate, but totally off without. It took me some time to figure it out - Pentax service did not.
Besides that there are several other things that all have an impact on ultimate sharpness.

[matroxication]

Wow, I thought that horse had well and truly bolted. Whether it is still worth it may depend on your view about how far away is the K1iii. My guess would be sometime in 2022.

Yeah, I was in the same understanding as well but apparently they can still order the parts and get the upgrade done.

---------- Post added 07-05-21 at 10:17 PM ----------

I have a K-3III and DA*60-250. Even with the new improved AF of the camera, focus is still a little inconsistent with PDAF. But LV CDAF is spot on 99%. I guess that is the limitation of PDAF.
On the other hand, I have this DFA 100 macro that is fairly accurate in PDAF but back focus in LV CDAF 100% of the time. I don't know what to make of it.

Thanks SBC. Yup agreed. My 100mm macro is almost always spot on in focusing and I rarely use live view with that. Problem with my 70-200 is, every day when I try to calibrate, I come up with different calibration setting and that too on both end of spectrum. +ve and -ve

---------- Post added 07-05-21 at 10:19 PM ----------

Are you calibrating with a tripod and tripod mount?
The 70-200 has different AF finetune values for 70/135/200 focal length, but you can typically find working solutions for all focal lengths within dof. The quick release plate on my K1 put pressure on the Phase AF Box. Finetuning results were very consistent with the plate, but totally off without. It took me some time to figure it out - Pentax service did not.
Besides that there are several other things that all have an impact on ultimate sharpness.

Thanks Zapp. That's interesting to know that the quick release plate is actually impacting the AF module. I do have ARCA swiss plate attached on my camera all the time as well. I used tripod for all my calibration testings.

---------- Post added 07-05-21 at 10:29 PM ----------

I just posted my camera and lens to C.R.Kennedy for calibration. Hope they do it correct the first time. In the past, I had to send my sigma 35 ART multiple times to them for calibration and they fixed it right the third time. Keeping my fingers crossed.

[stevebrot]

My expectation is to have sharp images at 2.8 in 200mm using phase detect focus.

Use center point to take advantage of the wide-aperture tuning of the center column points. If that is inconvenient, then another other option might be to tune one's expectations.


Question: Why the AF fine tune attempts? Is there obvious front/back focus?


Steve

[tibbitts]

I don't have any experience with the newer cameras, mostly with the K-5 and K-5ii (which do behave slightly differently due to different AF components) plus a little with a K-70. I was pretty content with PDAF with my f4 and slower lenses for my older 6mp and 10mp bodies, but once I added some f2.8 lenses plus went to 16mp, things fell apart. Even with factory new lenses, sometimes calibration would be required past the +/-10 on my bodies (why so restrictive?), and I couldn't even use debug mode to reset the baseline since some lenses would be on opposite ends of the scale. Pentax/Precision adjusted one of my new lenses under warranty that got it perfect (from being off by 10) at some focal lengths, but not others. It not just a Pentax thing: I have problems with third-party lenses as well, even after in-warranty adjustments. With zooms I've never overcome needing needing different calibrations at different focal lengths. Then when I added an f2.8 macro... now the problem was needing different calibrations at different focusing distances. So I've thrown in the towel and use CDAF, now that all my cameras support live view. Except with a couple of my longer lenses and the K-70: it often just can't focus a couple of them (like the 60-250 - often just hunts) even in live view. Usually it just hunts, and sometimes when it actually locks it does so with completely missing focus. And then there are certain subjects that will sometimes defeat even CDAF (like some knots in board lumber - which is surprising since they resemble resolution test targets.) So with my equipment my solution has been to moderate my expectations.

[matroxication]

Use center point to take advantage of the wide-aperture tuning of the center column points. If that is inconvenient, then another other option might be to tune one's expectations.


Question: Why the AF fine tune attempts? Is there obvious front/back focus?


Steve

Hi Steve,

I always use select focus and use centre focus point most of the time. I also avoid recomposing when using aperture wide open. The main reason I bought this lens to shoot wide open and everyone were praising this lens for its sharpness across all focal length wide open and I intend to use it for outdoor functions. My wife threatened me with divorce if I purchased this lens :P
But when I tested it, its kind hit and miss. The focus is blazing fast compared to all my other lens but the accuracy is what the question is. Had front focus issue on one day and when I calibrate, other focal length are not sharp enough with varying distance. Also this is the first time am calibrating setting from -ve to +ve. Usually lens either front focus or back focus and its easier to fix it but this one confuses me. The sharpness which am comparing to, is using the same lens in live view. Even with slower shutter speed and with camera shake, the images taken in live view focus it right. The comparison is more visible when you take images if eye lashes, skin pattern etc... on the whole, the picture looks ok but when you compare it with live view image, then we would know the difference in sharpness its lacking. Also when the image is not correctly in focus, it introduces noises as well even with lower ISO setting such as 400 or 800.

---------- Post added 07-06-21 at 04:58 PM ----------

I don't have any experience with the newer cameras, mostly with the K-5 and K-5ii (which do behave slightly differently due to different AF components) plus a little with a K-70. I was pretty content with PDAF with my f4 and slower lenses for my older 6mp and 10mp bodies, but once I added some f2.8 lenses plus went to 16mp, things fell apart. Even with factory new lenses, sometimes calibration would be required past the +/-10 on my bodies (why so restrictive?), and I couldn't even use debug mode to reset the baseline since some lenses would be on opposite ends of the scale. Pentax/Precision adjusted one of my new lenses under warranty that got it perfect (from being off by 10) at some focal lengths, but not others. It not just a Pentax thing: I have problems with third-party lenses as well, even after in-warranty adjustments. With zooms I've never overcome needing needing different calibrations at different focal lengths. Then when I added an f2.8 macro... now the problem was needing different calibrations at different focusing distances. So I've thrown in the towel and use CDAF, now that all my cameras support live view. Except with a couple of my longer lenses and the K-70: it often just can't focus a couple of them (like the 60-250 - often just hunts) even in live view. Usually it just hunts, and sometimes when it actually locks it does so with completely missing focus. And then there are certain subjects that will sometimes defeat even CDAF (like some knots in board lumber - which is surprising since they resemble resolution test targets.) So with my equipment my solution has been to moderate my expectations.

thanks tibbits. I completely agree since I was not even bothered about calibration when I was using K30. But moving to K1, I got all these calibration issues. Apart from the focus consistency in CDAF, I just hate taking images using it due to the noise/sound it makes. As if my K1 is having a bad cough every time I take an image with CDAF. The reason I now avoid any third party lenses is due to these issues and thought Pentax lenses will be better. That is the reason I bought the DFA* lens in the first place since it should be superior. But probably I need to change my expectation but could not digest it due to the lens cost. Need to wait and see what the service center is going to come back with.

[pschlute]

Even with slower shutter speed and with camera shake, the images taken in live view focus it right. The comparison is more visible when you take images if eye lashes, skin pattern etc... on the whole, the picture looks ok but when you compare it with live view image, then we would know the difference in sharpness its lacking.

I am confused now as to whether your issue is a general "sharpness" issue or a back/front focus issue.. The two are entirely separate.

[matroxication]

Hi Pschlute, its bit of both but they are linked I guess. I had issue with front focussing when tested with Spyder lenscal and I did the calibration based on that. But still the focus is not consistent across all distances. And it terms of sharpness, when I tested with my daughter outdoor, its not consistent when compared to CDAF and lot of times its not sharp. With background blur, you might think it is sharp since image pop out, but when compared to CDAF image, you will know clearly its not. Most of my pictures are taken at 200mm at f2.8. I tested with 3d objects at home for calibration and each time its different calibration settings and it seems to be better at one distance but not for all. If I go with dot tune method, its different setting every time even though its in controlled environment. With DIY method using measuring tape, its good for close distance but not when images taken at 3 to 4 meters. I even tried calibrating subject at infinity, but still it does not help.

I can understand CDAF focus is consistent but its also more forgiving even when using low shutter speed or having more camera shake when compared to PDAF. Its easier to use it with my younger daughter although I dont like using CDAF much.

[sbc]

Just crossed my mind. When you test focus, do you reset the lens twice each time? This is what I mean. Set to infinity, focus, shoot, set to minimum, focus, shoot. Adjust micro AF setting and repeat. You will find one of the two photos will be sharper. The idea is to settle on a setting that has both of these two photos equally sharp. It will NOT be the sharpest, which will be somewhere in the middle between the two. Pentax PDAF seems to stop short of the actual sharpest focus position.

[matroxication]

Thanks sbc. Yes, I usually refocus between each test shots. I keep my hand or any object and let the lens hunt for focus and then take next shot. Challenge is, even with that method and distance, if I can get correct calibration, when the distance changes then the focus is inconsistent and calibration value might be different. I understand that depth of field is very thin at 200mm and f2.8, but if CDAF is accurate all the time, I expect at least PDAF should be accurate majority of time.

[stevebrot]

The main reason I bought this lens to shoot wide open and everyone were praising this lens for its sharpness across all focal length wide open and I intend to use it for outdoor functions.

Based on the test images from the Pentax Forums detailed review of the D FA* 70-200, I would have to agree with their assessment that best sharpness was attained at mid-range for the lens with very acceptable, but less impressive results at 70mm and 200mm. I would not expect any 70-200ish zoom to be consistently spectacular through its entire range.

Touching back on PDAF performance at 200mm and f/2.8, even under ideal controlled conditions PDAF is fairly imprecise by nature. As a result, even when a lens is perfectly calibrated to the camera for accuracy, a sampling of say 20 focus attempts will show a fair number that are front or back focused. The number of misses will increase with wider aperture (due to DOF) and/or lessened sharpness* to the detector.

If it were me, I would fine tune to the lens wide-open for a focal length at mid-range and let the focal length extremes fall where they may. If you need "tighter" performance, your best option would be to let CR Kennedy do whatever they do to optically adjust the lens and do whatever magic they also apply to the camera.

Good luck.


Steve

* Optical softness or subject ambiguity. The PDAF sensor likes abrupt black/white boundaries, preferably vertical.

[sbc]

Thanks sbc. Yes, I usually refocus between each test shots. I keep my hand or any object and let the lens hunt for focus and then take next shot. Challenge is, even with that method and distance, if I can get correct calibration, when the distance changes then the focus is inconsistent and calibration value might be different. I understand that depth of field is very thin at 200mm and f2.8, but if CDAF is accurate all the time, I expect at least PDAF should be accurate majority of time.

Yes. I too have that problems with some of my lenses - different AF settings for different distance and focal length. Maybe Ricoh should invent a new Accurate Focus AF Priority mode. Just when the mirror flips up, the CDAF will adjust AF a final time before taking a photo. It WILL be slower but will be a good tradeoff in some situations. Just like hybrid AF with on sensor PDAF.

[matroxication]

Based on the test images from the Pentax Forums detailed review of the D FA* 70-200, I would have to agree with their assessment that best sharpness was attained at mid-range for the lens with very acceptable, but less impressive results at 70mm and 200mm. I would not expect any 70-200ish zoom to be consistently spectacular through its entire range.

Touching back on PDAF performance at 200mm and f/2.8, even under ideal controlled conditions PDAF is fairly imprecise by nature. As a result, even when a lens is perfectly calibrated to the camera for accuracy, a sampling of say 20 focus attempts will show a fair number that are front or back focused. The number of misses will increase with wider aperture (due to DOF) and/or lessened sharpness* to the detector.

If it were me, I would fine tune to the lens wide-open for a focal length at mid-range and let the focal length extremes fall where they may. If you need "tighter" performance, your best option would be to let CR Kennedy do whatever they do to optically adjust the lens and do whatever magic they also apply to the camera.

Good luck.


Steve

* Optical softness or subject ambiguity. The PDAF sensor likes abrupt black/white boundaries, preferably vertical.

Agreed Steve, I was primarily looking for a 200mm 2.8 lens and was very close to opt for DA* 200 since its less than half the price of this one and its a prime lens. But since this is zoom and everyone praised for its sharpness, went for it in last minute. Lets wait and see what C.R.Kennedy is going to advise. Surprisingly, this is the only stock they have am hoping they have a test lens to compare. I have also asked them to check the AF module on the camera as well.

---------- Post added 07-06-21 at 08:57 PM ----------

Yes. I too have that problems with some of my lenses - different AF settings for different distance and focal length. Maybe Ricoh should invent a new Accurate Focus AF Priority mode. Just when the mirror flips up, the CDAF will adjust AF a final time before taking a photo. It WILL be slower but will be a good tradeoff in some situations. Just like hybrid AF with on sensor PDAF.

My understanding is that to upgrade to a better AF technology, Pentax had to change its mount and they took decision based on huge customer base who still use legacy lens.

[stevebrot]

My understanding is that to upgrade to a better AF technology, Pentax had to change its mount and they took decision based on huge customer base who still use legacy lens.

That is an interesting rumor, but truth is that the only significant difference between what Pentax does and what Nikon does is the actual PDAF sensor hardware (more AF points) and the electronics running the show (superb and high proprietary algorithms). There is nothing intrinsic to the mount that determines AF performance.


Steve

[sbc]

My understanding is that to upgrade to a better AF technology, Pentax had to change its mount and they took decision based on huge customer base who still use legacy lens.

No. What I am putting forward for a far fetched idea is that Pentax camera AF with PDAF, the mirror flips up, CDAF takes over, locks focus and snap.
Anyway, I am just exploring ideas, nothing serious.