K3 III: AF-C on static objects

[KPM2]

Hello

I haven't had the K3 III for that long and I'm still testing it out to get to know it better. Yesterday I noticed something on the AF.C that I don't like at all: I simply focused on static objects in AF-C and the following occurred: Although the algorithm can determine that it has nothing more to do after the first successful focus, since the object doesn't move at all, the AF-C performs very often small objective movements occur. The lens is then focused in repeating small back and forth steps. My KP, K5 and K1 don't do that in their AF-C on static objects, they focus once and that's it. I even used the K3 III with a tripod to rule out the possibility that my own slight shaking could cause this, but it happens even on the tripod.

One example (with tripod use)

The scene (yust one example of a lot other objects I did try out)



and crops for to see what happens:

perfect focus:



but the AF-C did not stop focusing (like the KP, K5 and the K1 do here), it constantly moved the focus back and forth a little bit, to see in the next picture that has now:

backfocus



I think Pentax should take a look at why the AF-C of the K3 III often just doesn't come to a standstill on non-moving objects.

best regards KPM2

 

[John Venables]

Which version of firmware is your camera?

The AF-c on the K3iii has a lot more options than previous pentax cameras.

More options were added with firmware update 2.00

see https://www.ricoh-imaging.co.jp/english/products/k-3-3/firmup/

See menu still image / 1 AF with Viewfinder

scroll down to Focus Sensitivity in AF.C

There are five choices

５：Emphasize Trackability
AF Tracking mechanism activated when the subject makes even a slight motion in the direction of depth
４

３：Standard
Conventional AF tracking mechanism, set as default
２

１：Emphasize Stability
AF Tracking mechanism activated when the subject makes a large motion in the direction of depth.

To achieve the result you want you need to choose sensitivity 1.

 

[KPM2]

Hello John Venables

Which version of firmware is your camera?

The newest

The AF-c on the K3iii has a lot more options than previous pentax cameras.

More options were added with firmware update 2.00

see https://www.ricoh-imaging.co.jp/english/products/k-3-3/firmup/

See menu still image / 1 AF with Viewfinder

scroll down to Focus Sensitivity in AF.C

I had try that too: it makes no different.

These settings only determine the behavior when the AF-C detects a change in phase position. But with my static objects there is no change in phase position. In my last thread I posted pictures from a bicycle race (i.e. a kind of bicycle test). Even when the riders were so close that at 450mm only the head and upper body was visible in the scene, the AF-C was able to follow very often. In other words: When there is a movement, the algorithm doesn't have the time for such ''games'', but when the object stands still, it falls into them. I do not know why. All I know is that my KP, K5 and K1 just don't do it.

There are five choices

５：Emphasize Trackability
AF Tracking mechanism activated when the subject makes even a slight motion in the direction of depth
４

３：Standard
Conventional AF tracking mechanism, set as default
２

１：Emphasize Stability
AF Tracking mechanism activated when the subject makes a large motion in the direction of depth.

To achieve the result you want you need to choose sensitivity 1.

best regards. KPM2

 

[The Squirrel Mafia]

Weirdness. Kobie has done a few videos about the sensitivity 1 for extremely slow subjects.

https://www.youtube.com/@KobieMC/videos

^ There are like 4 videos in there that tack about stability & sensitivity 1.

But yeah. Maybe AF.S is the only way to go when doing still life on the K-3III?

 

[ozdean]

You can set the sesitivity of the AFC.

Use AFS is best.

--
Regards Dean - Capturing Creation
N.B. All my Images are Protected by Copyright

 

[MightyMike]

You're asking an algorithm to track something that isn't moving except that the algorithm is expecting movement so now its confused, it doesn't know what you want in focus because the item you've focused on isn't moving. Computer algorithms are far simpler than our eye-brain communication, you can't expect them to read your mind or to figure out that you don't want it to do what it was programmed to do. Why else would there be at least two AF choices available, one for moving subjects and one for static subjects!

 

[Ian Stuart Forsyth]

You're asking an algorithm to track something that isn't moving except that the algorithm is expecting movement so now its confused, it doesn't know what you want in focus because the item you've focused on isn't moving. Computer algorithms are far simpler than our eye-brain communication, you can't expect them to read your mind or to figure out that you don't want it to do what it was programmed to do. Why else would there be at least two AF choices available, one for moving subjects and one for static subjects!

I have never had this problem when using AF-C with other manufactures, matter of fact 99% of the time I use AF-C for about everything I shoot

 

[KPM2]

Hello MighthyMike

You're asking an algorithm to track something that isn't moving except that the algorithm is expecting movement so now its confused, it doesn't know what you want in focus because the item you've focused on isn't moving. Computer algorithms are far simpler than our eye-brain communication, you can't expect them to read your mind or to figure out that you don't want it to do what it was programmed to do. Why else would there be at least two AF choices available, one for moving subjects and one for static subjects!

I wrote that my K5, K1 and KP don't do that, so why do you think I can't demand that from an AF-C? And of course my camera knows what I want: I use only one AF point and when I focus, the camera knows that this AF point needs to be brought into focus. This is a very simple application!

For example a good result test of the K3 III AF-C:

AF-C with the first image set to focus priority:

So to test, point the camera at a static object (which is out of focus) and press down completely the shutter release button:

- the K5 almost never focused good on the object, it always released the shutter far too early (the AF motor was still running and after the picture also). The K5 was unusable here and you always had to wait until the AF motor came to a standstill and than you could press down completely the shutter release button.

- the K3 III is excellent here, the images of my static subject are in this test excellent in focus !

best regards KPM2

 

[FrankPhilipGroehl]

Hi, I almost always use AF-C on both equipments, Pentax and Olympus. When it comes to static objects / scenary I know that the AF will hunt a bit before sticking fractions of a second. That's the way it is with modern AF-systems. They are extremely fast and always calculating if you don't switch to AF-S. Guess, that the K3markiii is highly sophisticated in terms of AF-C nowadays and will not hold up completely for recalculation (quicker or slower settings) until you change over to the "real" AF-S where it knows that once AF is acquired, no further calculation is needed... - I'm sure you can customize the buttons to be able to quickly change in a situation like you described. Krgds, Frank

 

[MightyMike]

Hello MighthyMike

You're asking an algorithm to track something that isn't moving except that the algorithm is expecting movement so now its confused, it doesn't know what you want in focus because the item you've focused on isn't moving. Computer algorithms are far simpler than our eye-brain communication, you can't expect them to read your mind or to figure out that you don't want it to do what it was programmed to do. Why else would there be at least two AF choices available, one for moving subjects and one for static subjects!

I wrote that my K5, K1 and KP don't do that, so why do you think I can't demand that from an AF-C? And of course my camera knows what I want: I use only one AF point and when I focus, the camera knows that this AF point needs to be brought into focus. This is a very simple application!

For example a good result test of the K3 III AF-C:

AF-C with the first image set to focus priority:

So to test, point the camera at a static object (which is out of focus) and press down completely the shutter release button:

- the K5 almost never focused good on the object, it always released the shutter far too early (the AF motor was still running and after the picture also). The K5 was unusable here and you always had to wait until the AF motor came to a standstill and than you could press down completely the shutter release button.

- the K3 III is excellent here, the images of my static subject are in this test excellent in focus !

best regards KPM2

Was the test done on the exact same subject? and do you really know how big the AF point really is? I can tell you its larger than what is represented, so which part of the AF point is it using to determine what is in focus and is the AF point large enough to choose more than one focal plane and therefore in looking for a moving subject its not sure which part of the focus point to use since the subject doesn't appear to be moving... or does it because different parts of the focus point at different focal planes look very similar to the algorithm so it could jump on the assumption that the similarity is moving. There are likely more variables and complexities than you're imagining here.

 

[MightyMike]

You're asking an algorithm to track something that isn't moving except that the algorithm is expecting movement so now its confused, it doesn't know what you want in focus because the item you've focused on isn't moving. Computer algorithms are far simpler than our eye-brain communication, you can't expect them to read your mind or to figure out that you don't want it to do what it was programmed to do. Why else would there be at least two AF choices available, one for moving subjects and one for static subjects!

I have never had this problem when using AF-C with other manufactures, matter of fact 99% of the time I use AF-C for about everything I shoot

Since when has Pentax ever been as good as other manufacturers in AF? The other manufacturers have more time, money, resources and processing power in the cameras and therefore will always have a more effective AF system.

 

[Mac McCreery]

I swear by back button AF.

 

[Stihlmania]

Turn on subject recognition in the AF with Viewfinder menu. It will lock the movable focus point which you position the camera on to where you want the focus point, which will stop hunting in AF-C. You can see this in the viewfinder. Best ( fastest also) option for now is AF-S though..

 

[MightyMike]

I swear by back button AF.

That is one feature I could never feel comfortable using, I tried it once and quickly switched back, but I do understand why people like it.

 

[Paul_R_H]

Hi

I have exactly this problem, and have had it since I first got my K3 iii more than two years ago. I've started threads about it here and on the other forum.

The problem was so reproducible that Pentax UK, via the excellent SRS Microsystems, took the camera back and gave me a new one. It was just the same…

Some observations:

• I have always kept the firmware up to date

• That means I have been able to experiment with the new functions mentioned in this thread as they've become available, but that doesn't help. Subject recognition is tuned on, and I tried all the different 'trackability' settings.

• I've often cleaned the AF sensor with a blower brush. It doesn't help

• It gets worse when I've been shooting a lot: is something becoming overheated?

• It happens only with lenses of focal length shorter than 30mm. So the DA16-85 when zoomed towards 16mm but not at >30mm. This is the lens I use most. The same problem occurs with the DA15 Limited, and the FA28, both screw-drive lenses, but not the screw-drive FA135. And fortunately not with the 550-33PLM, the fastest and best-focussing lens I own.

• I use back-button focussing. While I understand the idea that 'the system is expecting movement in AF-C' if there's no movement it shouldn't adjust focus.

• If I disable back-button focus and use a half-press of the shutter, the same thing happens if I hold the button

So my way of working is…

• It's a failure of the PD system and doesn't happen in live view. So sometimes I use LV for static subjects when I want to be sure

• In view of the idea that 'the system is expecting movement…' I have trained myself to touch the back button once for static subjects and then release it

• Most of all, I always check focus on the screen. Always. And take several shots

Paul

 

[MikeSul]

Isn't that how is supposed to work? It constantly looks for focus as long as the button is pushed but stops looking when you release the BB.

 

[Paul_R_H]

Indeed. It's supposed to look constantly for focus while you have the button pressed.

And if the focussed object doesn't change distance, well then its constant looking should give a constant result.

But it doesn't. It gets two results (on correct, one incorrect) and hunts between those two.

And sometimes, the incorrect one is the one it arrives at first. So if at that point you release the button, it stays incorrect.

Fortunately, it usually arrives at the correct answer first. But not always, and that's why I always check on the screen afterwards.

Paul

Isn't that how is supposed to work? It constantly looks for focus as long as the button is pushed but stops looking when you release the BB.

 

[William the X-T5 guy]

You're asking an algorithm to track something that isn't moving except that the algorithm is expecting movement so now its confused, it doesn't know what you want in focus because the item you've focused on isn't moving. Computer algorithms are far simpler than our eye-brain communication, you can't expect them to read your mind or to figure out that you don't want it to do what it was programmed to do. Why else would there be at least two AF choices available, one for moving subjects and one for static subjects!

I have never had this problem when using AF-C with other manufactures, matter of fact 99% of the time I use AF-C for about everything I shoot

Well, you have with the K3III. The solution is to flick the switch over to AF-S when the subject isn't fleeing.

At the same time, it's good to note it and perhaps do a customer feedback report. It may be an overlooked bug that is fixable.

 

[Paul_R_H]

I'd call that a workaround not a solution. The very point of back-button focus is this:

You never have to do the switch, because the shutter button works the shutter and the back button works the focus and they are decoupled. If it's a static subject, you press the back button and then the shutter. If you release the back button first you can focus and recompose. If the subject moves, or you suddenly choose a new subject that's moving, well you just need to keep the back button pressed.

Good explanation here

https://photographylife.com/back-button-focus

Paul

[clip] The solution is to flick the switch over to AF-S when the subject isn't fleeing. [clip]

 

[Seahbc]

I am glad someone noticed this too. Found the K-3III's AF fidgety when I just got it. I ended up using AF-S for aerial displays.

I have not used AF-C since. Maybe I should try it again with latest firmware.