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05-13-2020, 05:29 AM   #1
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Autofocus issue K7 and PENTAX-DA 70mm F2.4 Limited

Before sending Lens and camera to the Pentax service point in Germany, I'd like to get your opinion:

When using 70mm Limited in Autofocus mode the focus point is completely wrong - see the comparison pictures attached, focus point is always on the match that is out of the line. In autofocus (German "Autofokus"), the last match is sharp, the orignal focus point is blurred). This seems to be a focus setting issue, because in manual mode (German: "manueller Fokus" - sorry I did not translate the subtitles), the focus point is sharp. Furthermore when manually turning the focus ring on the camera, the viewfinder gives me an indication, that the focus is ok (flashing red frame).

As I was assuming a camera issue I tried another lens PENTAX-DA 40mm F2.8 Limited: the problem does not show with this lens, so it seems to be an issue with the 70mm lens!


One additional questions: The four pictures were taken at the same time in raw (DNG) and processes by Rawtherapee using exactly the same configuration (sharpening switched off of course). I know there is a difference between smc and HD coating with an effect on the colors, but I am a bit surprised that the difference between 40mm and 70mm limited is so big.

Ulrich

(who deleted most of the weekends shooting )

Attached Images
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PENTAX K-7  Photo 
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PENTAX K-7  Photo 
05-13-2020, 06:15 AM   #2
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QuoteOriginally posted by ulrich Quote
Before sending Lens and camera to the Pentax service point in Germany, I'd like to get your opinion:

When using 70mm Limited in Autofocus mode the focus point is completely wrong - see the comparison pictures attached, focus point is always on the match that is out of the line. In autofocus (German "Autofokus"), the last match is sharp, the orignal focus point is blurred). This seems to be a focus setting issue, because in manual mode (German: "manueller Fokus" - sorry I did not translate the subtitles), the focus point is sharp. Furthermore when manually turning the focus ring on the camera, the viewfinder gives me an indication, that the focus is ok (flashing red frame).

As I was assuming a camera issue I tried another lens PENTAX-DA 40mm F2.8 Limited: the problem does not show with this lens, so it seems to be an issue with the 70mm lens!


One additional questions: The four pictures were taken at the same time in raw (DNG) and processes by Rawtherapee using exactly the same configuration (sharpening switched off of course). I know there is a difference between smc and HD coating with an effect on the colors, but I am a bit surprised that the difference between 40mm and 70mm limited is so big.

Ulrich

(who deleted most of the weekends shooting )
Hello Ulrich,
" that the focus is ok (flashing red frame)". If is flashes and is red it means that it is unsharp, it should be green and not flashing (that is in LV). If you see a red flash in the viewfinder it indicates the point where the AF is trying to focus at, if it flashes it means it can not focus, in the viewfinder the hexagon at the bottom of the VF should continuously light up green.The first picture actually is sharp, from the two matches at the top and above that. So the question is at what point did the AF catch focus. As for the 40mm, the AF is sharp in the middle.You can not compare them in my opinion, because of the different focal length and DOF. Did you make the pictures with spot AF?
I own the K-7 as well and I know it is a lot of harder to focus with. You can try the AF adjust option in the menu and change the setting for just the 70mm. In the first picture I can see some misfocusing, but I can not conclude if it is the lens that is at fault or that you aimed at the wrong match.
05-13-2020, 06:43 AM   #3
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In all pictures I was pointing the focus point to the same match: The one that is out of the line! And pushed the button, when AF was giving ok.

Autofocus was in spot mode.

What I meant with the indication (actually it was not blinking, it just poped-up) was in manual mode, when the camera tells you "yes this is the focus I would set in AF mode" - so the AF measuring seems to be ok.
This is the effect in the first picture: The measuring gave ok for the focus point in the match "out of the line" (... I should have colored it ...) but the focus setting is on the match on top.

Maybe this is a stupid question: "AF adjust option" AFAIK this was added in K5 (or later) and is not available in K7, or where do I find it?

Thanks for your reply!
Ulrich

Last edited by ulrich; 05-13-2020 at 07:16 AM.
05-13-2020, 07:25 AM   #4
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05-13-2020, 08:01 AM   #5
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QuoteOriginally posted by ulrich Quote
In all pictures I was pointing the focus point to the same match: The one that is out of the line! And pushed the button, when AF was giving ok.

Autofocus was in spot mode.

What I meant with the indication (actually it was not blinking, it just poped-up) was in manual mode, when the camera tells you "yes this is the focus I would set in AF mode" - so the AF measuring seems to be ok.
This is the effect in the first picture: The measuring gave ok for the focus point in the match "out of the line" (... I should have colored it ...) but the focus setting is on the match on top.

Maybe this is a stupid question: "AF adjust option" AFAIK this was added in K5 (or later) and is not available in K7, or where do I find it?

Thanks for your reply!
Ulrich
Hello again,
Go to menu C6 under number 37 option 2. There you find AF adjust. Well, if your 40mm pictures are spot on and so did your 70mm MF then it must be combination camera/lens when using AF through the viewfinder. If you do the same again but now with AF Live View do get a good result then? I know that autofocus with the K-7 can be very good in LV, and not so when using the viewfinder. So I take a picture with VF and if I do not like the result I do it again using LV.
05-14-2020, 12:02 AM   #6
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Great support here! Thank you for the quick reply, I'll check later and come back.
Ulrich
05-14-2020, 12:50 PM   #7
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Awesome! Found the setting and I really don't know why I did not see that before. Had to set it to +3 for one lens and -1 for another, but it seems that it is moving and needs readjustment after a while. So I will need some more test in different light and different distances.
I know the camera is old and there are some more minor things, that do not work properly anymore, but it needs to hold until the new K3 is coming....

Thank you again.

Ulrich
05-14-2020, 03:05 PM   #8
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QuoteOriginally posted by ulrich Quote
Awesome! Found the setting and I really don't know why I did not see that before. Had to set it to +3 for one lens and -1 for another, but it seems that it is moving and needs readjustment after a while. So I will need some more test in different light and different distances.
I know the camera is old and there are some more minor things, that do not work properly anymore, but it needs to hold until the new K3 is coming....

Thank you again.

Ulrich
Your welcome. Like you I experience that K-7 is a bit unstable when focusing. It does shift sometimes after adjusting. But sometimes the results are outstanding. Beautiful colours and very much (fine) detail.

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