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10-27-2021, 01:13 AM   #1
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Can someone check the accuracy/difference of all AF points in AF-S Select

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.


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10-27-2021, 01:34 AM   #2
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This shows which focus points are cross type.
Ahh sorry you already saw it


---------- Post added 10-27-21 at 08:44 AM ----------

This thread shows eye AF working.
https://www.pentaxforums.com/forums/210-pentax-k-3-iii/424237-eye-af-viewfin...lly-works.html
10-27-2021, 01:48 AM - 1 Like   #3
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You really do need to test this on a tripod to rule out the possibility of your own movement affecting results (I know you know this), and run repeated tests for the focus points you believe are and aren't working as expected to make sure the failure to focus is happening routinely rather than just occasionally.

Methodology is critical for AF tests... I speak from experience

It would also be extremely helpful to post some images (100% repro crops) so we can see what you mean by missed focus, and mark them to show us what you were focusing on...
11-07-2021, 02:29 PM   #4
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Edit: I'm reffering only to 16-50 PLM, sorry for the confusion.
The AF fine adjustment seems to sorted it out.;D
Gotta learn some patience.;D


I just tested the lens and it seems that in low and artificial light it only focuses correctly using central, f2.8, focus points.


Last edited by Settesz; 11-08-2021 at 02:02 AM.
11-07-2021, 02:50 PM   #5
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QuoteOriginally posted by Settesz Quote
Edit: Ok, AF fine adjustment sorted it out.;D
Gotta learn some patience.;D


I just tested the lens and it seems that in low and artificial light it only focuses correctly using central, f2.8, focus points.
Did you have the same problem as the OP, or are you the OP with a different user name?
11-07-2021, 03:51 PM - 1 Like   #6
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I had similar problem. I checked the lens once I got it and it was fine, but I did it using central AF point only.
Today I was doing a portraits session and noticed many of my pictures were out od focus, I had to switch to DA* 55 because 16-50 was a real mess.
Once I got home I tested the lens again and searched the forum - found this thread. My problem was pretty much the same. Fortunatly AF fine adjustment seems to have worked and now lens focuses fine with all af points.
Its weird that it focused correctly with central points but needed correction for all the rest.
Anyway I'm happy it worked out, this lens is very fast and sharp as hell, wouldn't want to return it to the store.
11-08-2021, 12:21 AM   #7
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@Settesz; I think you wrote me a private massage, since you read my problems in the 16-50 PLM thread and after my private answer, you jumped right in this thread... so others could be confused, because you started talking about "a" lens.

But - regarding your adjustment : it makes me wonder, that it does not affect your central sharpness, when you make adjustment only for outer focal points.

11-08-2021, 01:48 AM   #8
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Oh, right, sorry for the confusion, I was indeed reffering to 16-50 PLM. Will test some other lenses later tho.
Yes, it is kinda weird that adjustment doesnt seem to interfere with f2.8 AF points.

EDIT: Okay, it seems my 16-50 PLM needs +7 AF adjustment, but it does not apply to cental f2.8 AF points.
I tested 3 more lenses (DA*55, DA*50-135 and HD DA 16-85) and none of them exhibits the same behaviour, they work fine with all AF points without any adjustments.

Last edited by Settesz; 11-08-2021 at 02:38 AM.
11-13-2021, 02:03 PM   #9
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I just got my 16-50 PLM and put it on my K-3III. Center point is dead on but the first left and down misses. I do not understand why... Using the DFA24-70@50 and the same fp is dead on.
11-13-2021, 02:12 PM   #10
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QuoteOriginally posted by Tjompen1968 Quote
I just got my 16-50 PLM and put it on my K-3III. Center point is dead on but the first left and down misses. I do not understand why... Using the DFA24-70@50 and the same fp is dead on.
Only the first left and down AF point, or others too?
11-14-2021, 02:49 AM   #11
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After doing some intensive testing of 16-50PLM with k3iii it seems my copy autofocuses correctly with center points but needs -7 to -9 microadjustment for all the others. Unfortunatly microadjustments messes the center points accuracy after all. Its very frustrating, will send it for repairs I guess.

@Tjompen1968 can you check if other AF points work correctly?

Last edited by Settesz; 11-14-2021 at 03:06 AM.
11-14-2021, 07:18 AM   #12
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QuoteOriginally posted by BigMackCam Quote
Only the first left and down AF point, or others too?
Pretty much all points exept center needs some kind of adjustment. Much more on the right side than on the left side.
Putting other lenses and the problem dissapears.

---------- Post added 11-14-21 at 03:21 PM ----------

QuoteOriginally posted by Settesz Quote
After doing some intensive testing of 16-50PLM with k3iii it seems my copy autofocuses correctly with center points but needs -7 to -9 microadjustment for all the others. Unfortunatly microadjustments messes the center points accuracy after all. Its very frustrating, will send it for repairs I guess.

@Tjompen1968 can you check if other AF points work correctly?
Nope, others does not. See comment above.


I will probably send it back since I find the DFA24-70 to be sufficient in terms of IQ compared. For wider shots I will use the DFA15-30. This I have to test more when I have better daylight before taking the final decision. The IQ of the lens is impressive when it nails focus.
11-14-2021, 07:35 AM   #13
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Seems we have a similar problem.
Makes me wonder how widespread it is.


QuoteOriginally posted by Tjompen1968 Quote
Pretty much all points exept center needs some kind of adjustment. Much more on the right side than on the left side.
Putting other lenses and the problem dissapears.

---------- Post added 11-14-21 at 03:21 PM ----------



Nope, others does not. See comment above.


I will probably send it back since I find the DFA24-70 to be sufficient in terms of IQ compared. For wider shots I will use the DFA15-30. This I have to test more when I have better daylight before taking the final decision. The IQ of the lens is impressive when it nails focus.
11-14-2021, 08:19 AM   #14
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QuoteOriginally posted by Settesz Quote
Seems we have a similar problem.
Makes me wonder how widespread it is.
I will call the service center tomorrow to see what they say about it.
11-14-2021, 08:51 AM   #15
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Can you check if it focuses correctly in live view?

I don't know what happened but after checking the live view lens started to focus correctly thru an ovf without any corrections.:P

QuoteOriginally posted by Tjompen1968 Quote
I will call the service center tomorrow to see what they say about it.

Last edited by Settesz; 11-14-2021 at 09:15 AM.
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