Hello,
I posted my problem already in a different thread to the 16-50 PLM and also in the German Pentax forum.
To make it short:
I figure out, that I´ve several missed shots of persons, where I was convinced, that I put an outer focus point on the eye.
I tried this at home right now with a focus sheet with enough contrast structure exact in the focus area.
Lenses I used : as mentioned, the 16-50 2.8 PLM (tried @50 mm f2.8) , the 35 2.0 (tried @2.0) and the 55 1.4 SDM (tried @2.0 since 1.4 is not really representative in the outer areas due to really softness of my copy here).
I know there are some differences in the AF points (some 2.8 and some cross type and some only line type). But what makes me wonder is, that some.
What makes me wonder was, that the edges of the inner rectangle often don´t work….but the next outer worked perfect.
Can someone test this? As me right now very quick with totally free test equipment hand hold –I know I´ve to do this with full manually control and tripod….but I´ve not the time right now ….and honestly: it must work in my understanding.
Or is my understanding in moving the points and use them in this way wrong?
May be I´ve only a bad copy (second time unfortunately…first copy was with a dent)
Here my old text from the mentioned 16-50 PLM thread (There are already some comments from some members - thanks to them!):
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.