[Eric Seavey]

I have been using my new K3III for a while now and am confused what the best setting is for the autofocus for portraiture. Often photographers use single point on the eye for head shots and full body shots. Yesterday I did shot some photos, with my K3III set to AF S and Zone Select in the center (lenses: DA 50mm f1.8 and f/2.4 DA Limited set to F/3.5). This resulted in horrible front focus on most of my shots, where the center was barely in focus, but the head and feet were out of focus. I was hoping the zone select would set the focus optimally so that my entire subject would be in focus. When I kept that setting for head shots, it did the same, and I resorted to single point on the eye again so that the face would be in proper focus. Should I stick to single point autofocus for portrait photos? What is the zone autofocus for? I found it works fine when shooting at 45 degrees down at a table with various objects, and other similar situations, but portraits (full body and head shots) it just front focuses horribly where the center is barely in focus.

I wanted to make sure this was not a camera or lens problem and so I downloaded and printed a focus test page and set it up at a 45 degree angle. The focus is spot on using individual points for both lenses, so I need to understand better what the zone algorithm is for as well as the user selected 5-point region (In think is called Select S).

Any help with this is highly appreciated.

[biz-engineer]

I use face detect AF in live view (K1). It works rather well.

[bschriver11]

Sounds to me like your problem is depth of field and not a focus problem. You stated that the center was in focus which is the focus point you chose but the head and feet were out of focus. Depth of field depends on a number of things like aperture, focal length, and distance from camera to subject. A depth of field calculator might be helpful and can easily be found online.

[aslyfox]

have you read the " In Depth Review " yet

Pentax K-3 Mark III Review
Recommended Settings
The number of settings and customization options on the Pentax K3 III can be quite overwhelming at first. Below we present our recommended settings where they differ from the out-of-the-box defaults. . . .

Read more at: Pentax K-3 Mark III Review - Recommended Settings | PentaxForums.com Reviews

[Eric Seavey]

Sounds to me like your problem is depth of field and not a focus problem. You stated that the center was in focus which is the focus point you chose but the head and feet were out of focus. Depth of field depends on a number of things like aperture, focal length, and distance from camera to subject. A depth of field calculator might be helpful and can easily be found online.

No it is not a DOF problem, because the ground in front of the subject is in focus. It seems to me that the center of the DOF is in front of the subject instead of on the subject when I use zone select AF.

---------- Post added 11-27-2021 at 02:14 PM ----------

I use face detect AF in live view (K1). It works rather well.

Indeed, the live AF works well, however I prefer to use phase AF.

Thanks

---------- Post added 11-27-2021 at 02:21 PM ----------

have you read the " In Depth Review " yet





Read more at: Pentax K-3 Mark III Review - Recommended Settings | PentaxForums.com Reviews

Haven't read that until now. Like I said, zone AF is not good at all and front focuses. When I first received my K3III I used Auto, and it was getting confused a lot with contrasty backgrounds. I suppose I can try Auto AF again with the new firmware updates. Although I would be surprised if that would make any significant difference.

[Paul the Sunman]

I use face detect AF in live view (K1). It works rather well.

Isn't that just for LV?

[shyrsio]

I use single point "focus and recompose", I usually focus on one of the eyes, or in the middle of the eyebrows if I have enough DOF

[Settesz]

What did the zone focus on?
You've written that you've set zone on the centre-but of what?
To make subject recognition work you need to cover subjects face with it, this way AE sensor can find subjects eyes.
Works for me without a problem with sensible limitations (the smaller the face the harder it gets ).

[biz-engineer]

Isn't that just for LV?

Yes only in LV. Not a big deal for me, I use live view often especially with display tilted up or on the side. I just stand beside the camera to appreciate the subject / scene and glance back / forth between the display and the scene/subject. I find LV actually more convenient than looking through the OVF, especially since I wear eye glasses, I don't need to take my glasses on and off all the time. A few years back I wasn't a big fan of live view, I was used to composing through the OVF, but I gradually used live view more and more often. I particularly enjoy the outdoor view setting of the back LCD on the K1. Ironically, Ricoh promotes the OVF (as opposed to EVF) as the thing for keeping in touch with the subject when shooting, but I found that being beside the camera (and not behind the camera) is even better than OVF for keeping in touch with the subject.

[sarge]

Have you watched this video?

Youtu.be

Youtu.be

He does a good job explaining eye AF with the K-3III

[Larrymc]

Haven't read that until now. Like I said, zone AF is not good at all and front focuses. When I first received my K3III I used Auto, and it was getting confused a lot with contrasty backgrounds. I suppose I can try Auto AF again with the new firmware updates. Although I would be surprised if that would make any significant difference.

Have you tried to fine tune the autofocus for the problem lens?

I disagree that that Zone AF is no good, I use it all the time and it is reliably accurate in most situations. Here is an HD 35 Limited f/2.8 shot at f/2.8 it was shot hand held using focus and recompose I'm also attaching a 103% crop of the original focus point. It may not be the best focused portrait in the world but its but it certainly isn't front focused. The low res images here on the forum doesn't do it justice. You need to do a careful evaluation of the lens you're using and carefully fine tune it.

[Eric Seavey]

Have you watched this video?
https://youtu.be/L9XZC3bmddQ
He does a good job explaining eye AF with the K-3III

Interesting! Although he is working at f/8

[Eric Seavey]

Have you tried to fine tune the autofocus for the problem lens?

I disagree that that Zone AF is no good, I use it all the time and it is reliably accurate in most situations. Here is an HD 35 Limited f/2.8 shot at f/2.8 it was shot hand held using focus and recompose I'm also attaching a 103% crop of the original focus point. It may not be the best focused portrait in the world but its but it certainly isn't front focused. The low res images here on the forum doesn't do it justice. You need to do a careful evaluation of the lens you're using and carefully fine tune it.

This looks very good! I am starting to wonder if my camera has some problem.
I have the AF fine adjustment set to -10 for the Three lenses I use, and still it is front focused when doing portraits. Here is an example of a full body portrait and it is badly front focused, and the info of the photo. I just do not understand this inconsistent focus performance. Sometimes the focus is right on, and often it is not. The best results I am getting is when I use center spot focus.

[clackers]

Hi Eric,

In order, I think:

1. Set your shutter speed to around 1/200s even if you're using a tripod, that's a person you're shooting. 1/40s is not acceptable, they will move, even imperceptibly!

2. Set zone focus, on the head and let the K-3 III focus on her eyes for you, this is what you paid good money for! Make sure Subject Recognition is turned on in the menus.

3. If in style you are not a decisive shooter - there is a time gap between when you acquire focus and you actually take the shot - do AF-C instead of AF-S.

4. -10 for three lenses suggests there is a fault with your camera - return for exchange or repair within the warranty period.

[licht96]

Hello,

I must admit I´ve the same problem with myK3III….and – as written in a parallel thread - manly with the 16-50 PLM.
But all the other lenses show this inconsistent with OTHER AF than Spot/Centre Focus in AF-S.
In AF-C it´s working more or less good.Very curious since this is more complex.

But as @Eric Seavey I better choose AF-S for portraits since the movement (when “things” are slow and shutter speed high enough) because the AF-C really “Search” for movement and seems “disappointed” and fail often when things are not moving.

So all new features/grids/zones/auto-topics are not really reliable in my portrait work.

And now the news: I get my K3 III back from repair store (4 Weeks in repair!). On a small paper they wrote “Calibration” ….not more (I´m not a big fan of this very small communication of this service center here in Germany – but this is a different story).

But nothing changes this.

And since I read so much fantastic reviews of the new AF of the K3III I´m a little bit disappointed.

I often think I´m the only person with a Pentax who don´t use it for landscape an birds when I look at sample photos in the forum here ;-) But I think that is more or less the “problem” that it is not so easy or common to show friends/wife/children without their permission. So thanks to Eric Seavey: I´m not feeling alone.

Regarding my more or less parallel/similar problem written in the AF-S Select thread: When using outer AF points the failure is massive frontfocus, too!

And as well using this Zone AF: the points are showing that they find something (as in the portrait above I would say the middle of the body)…..but why is it totally out of focus? Ok the shutter was very slow as mentioned by another member, there might be some blur from movement….but you can see clearly at the ground the front focus. The leafs get sharper in front of the women (and I think it was only ONE example, and as me, he has a lot of more, otherwise he would not ask this)


So….I´m right before sending the 16-50PLMto services as well. Because it shows this very massive. I attached it for better comparison on my K3II. It´s not really good comparable, since the AF field is limited. But the front focus also behave when choosing outer AF-fields with really good contrast confirmation.

I´m now doing old fashion AF Spot/Center halfpressed and recompose…. But – as mentioned above: that’s not what I paid for.

---------- Post added 12-01-21 at 06:49 AM ----------

And I forget: this mentioned "5-point region (In think is called Select S)" doesn't´t work for me as well.


When I pout this "cross" on a face and half press, the cross changed only to the center point...ok...so far...so good.

But the face is not in focus!

When I use the normal Select with one AF filed, and have luck with an outer region: it´s better.

I don´t use this mode.

I thought in the beginning, that this works better with subject recognition, when there is really bad contrast or better nor edges ON ONE POINT...so It could help with the neighbor AF points...but not with faces :-(
or not with my camera :-(