[MMVIII]

There are two good articles on field curvature in lenses by Roger Cicala.
Roger Cicala: Understanding field curvature for fun and profit: Digital Photography Review
Roger Cicala: Understanding field curvature for fun and profit (part 2): Digital Photography Review
He explaines quite well what focussing strategy to use if your main subject and focus should be off center or other settings.

[house]

I would treat the issue as a fault with either camera or lens until you figure out what's going on. As mentioned all reviews so far has emphasised the well controlled field curvature.
Is the problem at the wide end or at all focal lenghts?

[MMVIII]

I would treat the issue as a fault with either camera or lens until you figure out what's going on. As mentioned all reviews so far has emphasised the well controlled field curvature.
Is the problem at the wide end or at all focal lenghts?

I also assume it is not field curvature. The second berry image does not have anything in the center where the focus would be. If focused with PD-AF the berry is maybe already outside the area covered with AF points and probably had to be recomposed?

I don't assume a problem neither with the lens nor with the camera, but more a new challenge for proper AF at the very periphery of the frame, that may be exposed more than before by the high MP count of the K-3 III and the smooth transition from very sharp to slightly OOF in the lens. Things, that might have not been noticed with previous equipment.

[gatorguy]

I also assume it is not field curvature. The second berry image does not have anything in the center where the focus would be. If focused with PD-AF the berry is maybe already outside the area covered with AF points and probably had to be recomposed?

I don't assume a problem neither with the lens nor with the camera, but more a new challenge for proper AF at the very periphery of the frame, that may be exposed more than before by the high MP count of the K-3 III and the smooth transition from very sharp to slightly OOF in the lens. Things, that might have not been noticed with previous equipment.

Yes, the left berries image was focused then recomposed. Good observation

I'm assuming the same, user error on my part, seeing as it's not readily evident in the shed shot. I'll be testing it more today.

[licht96]

Hm...can anyone explain the problem (maybe field curvature?) with an easy picture....?

I´m a little bit disappointed with the problem I face right now with this lens and the K3III.

I did´t have this problem before with the old 16-50 and the K3II - BUT: I did´t use the outer AF points with this old combo. Due to the lack of the AF Joystick (and I don´t like the use of the arrow keys), I mainly use the center to focus and than recompose.

With the same technique on the new K3III and the new 16-50 PLM - now problem: tack sharp @2.8.

But - as mentioned: when I recompose the picture before (!) and then use an outer auto focus point: total out of focus ....ok...not total...bit a little bit more off, to the one with center and recompose.
More visible @16mm than in 50mm.


I was so happy with the bigger AF field and the new Joystick....not this annoying moving of the camera....only cool "finding" right AF point in an already composed picture in the viewfinder....but now I´m more or less forced to go back to the old technique...

[BROO]

Hm...can anyone explain the problem (maybe field curvature?) with an easy picture....?

I´m a little bit disappointed with the problem I face right now with this lens and the K3III.

I did´t have this problem before with the old 16-50 and the K3II - BUT: I did´t use the outer AF points with this old combo. Due to the lack of the AF Joystick (and I don´t like the use of the arrow keys), I mainly use the center to focus and than recompose.

With the same technique on the new K3III and the new 16-50 PLM - now problem: tack sharp @2.8.

But - as mentioned: when I recompose the picture before (!) and then use an outer auto focus point: total out of focus ....ok...not total...bit a little bit more off, to the one with center and recompose.
More visible @16mm than in 50mm.


I was so happy with the bigger AF field and the new Joystick....not this annoying moving of the camera....only cool "finding" right AF point in an already composed picture in the viewfinder....but now I´m more or less forced to go back to the old technique...

The 25 (5x5) selectable AF points that occupy the middle square area of the viewfinder are f2.8 cross type.

What happens when you close the aperture down to f4 or f5.6 when using the outer AF points?

[licht96]

I am going to bed right now, so I can't try...
... but in my understanding the area focused on, will be sharp...but more due to the fact, that the object is now in the bigger area of sharpness created by physics of aperture change... not really due to better circumstances for the AF module.

When I want to separate an object from the back (mostly portrait) I want to choose 2.8 on the lens.

[repaap]

I am going to bed right now, so I can't try...
... but in my understanding the area focused on, will be sharp...but more due to the fact, that the object is now in the bigger area of sharpness created by physics of aperture change... not really due to better circumstances for the AF module.

When I want to separate an object from the back (mostly portrait) I want to choose 2.8 on the lens.

I’m not sure if stopping down the lens would do much of a difference. I don’t have PLM, I do have SDM. I can try tomorrow also to use points at the edges. Did you notice that it did focus on that point you did choose? What was that subject? Also was it darker than other things in your frame? These thing do matter as well as your chosen AF settings. I’v taken notice that there are things which does work best at certain settings. Auto for people and faces and eye, as well as for tracking them. SEL for things and bigger objects and bikes and what not. Spot for most precise chosen targets. If you focus with mid point and refocus at wide end , you’ll end up with your luck. Atleast with old SDM version, mostly due field curvature reasons.

[kinkindoll]

Just wondering what happening if the image is sharp and accurate when using live view focus to the edge or out of the centre but OVF behaved different ?

[reh321]

When I want to separate an object from the back (mostly portrait) I want to choose 2.8 on the lens.

I suspect you don’t put the subject of a portrait on the far side of the portrait.
You need to work extra hard if you do photograph a scene when the main subject is off to the side.

[gatorguy]

I suspect you don’t put the subject of a portrait on the far side of the portrait.
You need to work extra hard if you do photograph a scene when the main subject is off to the side.

I usually leave room to crop and adjust in post if I suspect I want to shift the subject to a far side of the frame while maintaining sharp focus.

[licht96]

Hm. I tried this now with other lenses. Same effect. A little bit sad for me. As mentioned: when shooting persons, I always took the eye in the middle AF point.
Sometimes I took the shot like this, but sometimes I recomposed halfed pressed to make the picture not so boring (yes crop is one idea - but when you are very close, you sometimes not have enough "room" to crop/recompose in post process).

So I always looked a little bit questioningly at pictures of people taken full body shots @f1.4. The center is mostly the center of the person....but the eye is sharp (when you have a good lens, with good sharpness to the edges).

Let´s take the case when this person has a lot of clothes, or a big stomach...than the center AF point would catch a focus which is more close to the lens than the eye.
Than I would have only two ideas:


a) take the center to the eye...recompose with half pressed button....and shoot (while hoping that 1. the person didn´t move in that time and 2. hoping that the influence of the angle from the initial starting point AF is not so big***

b) take the person after recomposing in the middle and find a dedicated off centered AF point for the eye

But b) seem not to work. I hoped for better handling this with the K3III with more AF points. I think it´s not a problem of this lens...I tried with the 11-18 as well....same effect.

May be someone can explain this a little bit better to me as I´m not so deep in the optics here ( ***as maybe visible here in this sentence).

I look a little bit envy at the videos of mostly mirrorless shooting people, who do exactly that. Or even more intense, since the AF points are going really right to the edges of the frame. Additional assisted by a green or yellow frame exactly to the eye. So they force this really to the outside of the frame, to get a full body shot with a sharp eye.

I know, that this are complete different AF systems!

....but I was hoping a little bit with the outer AF points and the Joystick to come a little bit nearer to this kind of "work"
As mentioned: my be someone can explain this to me...may be in a different topic here in the forum.

[repaap]

Hm. I tried this now with other lenses. Same effect. A little bit sad for me. As mentioned: when shooting persons, I always took the eye in the middle AF point.
Sometimes I took the shot like this, but sometimes I recomposed halfed pressed to make the picture not so boring (yes crop is one idea - but when you are very close, you sometimes not have enough "room" to crop/recompose in post process).

So I always looked a little bit questioningly at pictures of people taken full body shots @f1.4. The center is mostly the center of the person....but the eye is sharp (when you have a good lens, with good sharpness to the edges).

Let´s take the case when this person has a lot of clothes, or a big stomach...than the center AF point would catch a focus which is more close to the lens than the eye.
Than I would have only two ideas:


a) take the center to the eye...recompose with half pressed button....and shoot (while hoping that 1. the person didn´t move in that time and 2. hoping that the influence of the angle from the initial starting point AF is not so big***

b) take the person after recomposing in the middle and find a dedicated off centered AF point for the eye

But b) seem not to work. I hoped for better handling this with the K3III with more AF points. I think it´s not a problem of this lens...I tried with the 11-18 as well....same effect.

May be someone can explain this a little bit better to me as I´m not so deep in the optics here ( ***as maybe visible here in this sentence).

I look a little bit envy at the videos of mostly mirrorless shooting people, who do exactly that. Or even more intense, since the AF points are going really right to the edges of the frame. Additional assisted by a green or yellow frame exactly to the eye. So they force this really to the outside of the frame, to get a full body shot with a sharp eye.

I know, that this are complete different AF systems!

....but I was hoping a little bit with the outer AF points and the Joystick to come a little bit nearer to this kind of "work"
As mentioned: my be someone can explain this to me...may be in a different topic here in the forum.

If you are often shooting like that, it sounds that you need to get mirrorless camera.

I don’t really understand what is the problem … what I would do is that I’d use AF in auto mode. Keep AF hold and focus to that person you want to have focus in and AF will find eye/face, halfpress in order to hold the focus at this person even if she/he moves. Automode uses all AF points and uses also that image on that RGB sensor to fill out ’missing’ points/see what you are focusing at. In this way you get wht you are looking for. Try it if it won’t work, then I’m out of ideas ..

[BigMackCam]

Hm. I tried this now with other lenses. Same effect. A little bit sad for me. As mentioned: when shooting persons, I always took the eye in the middle AF point.
Sometimes I took the shot like this, but sometimes I recomposed halfed pressed to make the picture not so boring (yes crop is one idea - but when you are very close, you sometimes not have enough "room" to crop/recompose in post process).

So I always looked a little bit questioningly at pictures of people taken full body shots @f1.4. The center is mostly the center of the person....but the eye is sharp (when you have a good lens, with good sharpness to the edges).

Let´s take the case when this person has a lot of clothes, or a big stomach...than the center AF point would catch a focus which is more close to the lens than the eye.
Than I would have only two ideas:


a) take the center to the eye...recompose with half pressed button....and shoot (while hoping that 1. the person didn´t move in that time and 2. hoping that the influence of the angle from the initial starting point AF is not so big***

b) take the person after recomposing in the middle and find a dedicated off centered AF point for the eye

But b) seem not to work. I hoped for better handling this with the K3III with more AF points. I think it´s not a problem of this lens...I tried with the 11-18 as well....same effect.

May be someone can explain this a little bit better to me as I´m not so deep in the optics here ( ***as maybe visible here in this sentence).

I look a little bit envy at the videos of mostly mirrorless shooting people, who do exactly that. Or even more intense, since the AF points are going really right to the edges of the frame. Additional assisted by a green or yellow frame exactly to the eye. So they force this really to the outside of the frame, to get a full body shot with a sharp eye.

I know, that this are complete different AF systems!

....but I was hoping a little bit with the outer AF points and the Joystick to come a little bit nearer to this kind of "work"
As mentioned: my be someone can explain this to me...may be in a different topic here in the forum.

Let me attempt to simplify this... are you saying for "b)" that when you pick an off-centre AF point, the subject isn't in focus - and this happens with several lenses?

And this is on the K-3II, yes? Or on the new K-3III? I ask because I know the off-centre AF points work accurately on my K-3 and K-3II, since I've used them regularly (even though, as a general rule, I tend to focus and re-compose)...

[Lloyd_Christmas]

I got my copy today...ordered it Sunday night around midnight direct from Ricoh Imaging.
Fast delivery!
Checked the location and they are in Tucker, Georgia, not too far from me.
Shipping in the Atlanta metro area can be that fast.

Anyway it is a big beast and "DAYUM" it takes some clean photos!!!

#PentaxLives