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12-10-2020, 01:06 AM   #1
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Photos totally out of focus on the K-70

Hi,
a short time ago I bought the Pentax-M 50mm f/1.7 (a little gem) and made the experience that I wasnīt able to take sharp pictures with it. At least with focus confirmation. As soon as I focus how I see the image, almost all the pictures are sharp. This wouldnīt be an issue for me if I didnīt use "Catch-in-focus". The pics come out really blurry then. I used a test chart for front and back focus, finding out a front focus of about 6 cm (pretty hard for close-up and portrait shots, huh?), making the adjustment -10. As this Pentax lens has no info contacts the K-70 takes this adjustment for every other lens too. Is there any diy way of calibrating the lens, or is this something that should be rather done in a service? Otherwise I am well into 50000 actuations and the camera works fine, otherwise.
Thanks for your replies,
J.

12-10-2020, 02:12 AM   #2
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That looks weird. Can you maybe post an example photo or two?

That much of a misalignment is probably a lens issue, if the camera focuses well with other lenses...
12-10-2020, 02:30 AM   #3
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Did you check if the focussing is ok when you use live-view?
As Serkevan asked already, how is manual focussing through the viewfinder working for other lenses?
12-10-2020, 04:55 AM   #4
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Are you in AF.S? Are you using a tripod?

12-10-2020, 05:47 AM   #5
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Some full size sample pictures would help, preferably linked from a photo hosting site so that they are not downsized by the forum software.

I would be surprised if it were a problem with the lens. AF and AF confirmation can vary from lens to lens but this is usually with AF lenses, especially screw drive ones. Are you aware that the AF confirmation will only use the centre point AF with that lens, and it must be placed directly over the subject for it to work ?

Another thing you can try is to put the camera into LV and try the AF confirmation in that mode. How does that work ?

Finally, if you do need to use AF-FA menu to account for the M 50mm, as you have discovered it will affect all lenses, BUT only if you have the AF-FA menu set to APPLY ALL. For any AF lens you own you should individually calibrate them using the APPLY ONE menu, even if the adjustment is zero. Then exit the menu in the APPLY ONE setting. Now your AF lenses will be using any individual adjustment you have set for them (including zero), and if you mount the M lens you will find the menu will automatically default to the APPLY ALL setting you have used for the M lens.
12-10-2020, 09:09 AM   #6
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You can toggle the apply all on and off to apply it only when needed by that lens. Or put masking tape inside the cap with the adjustment needed if you have several lenses that need the apply all adjusted differently.
12-10-2020, 11:06 AM - 1 Like   #7
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QuoteOriginally posted by ShutterPro Quote
This wouldnīt be an issue for me if I didnīt use "Catch-in-focus".
CIF uses the same mechanism as focus confirm and neither is particularly precise (same focus twice in a row) though you should be getting similar results for both, minus the lag time for CIF.

QuoteOriginally posted by ShutterPro Quote
As this Pentax lens has no info contacts the K-70 takes this adjustment for every other lens too. Is there any diy way of calibrating the lens, or is this something that should be rather done in a service?
As noted above, your option for in-camera adjustment is to set correction to "all" as a temporary setting only. If you are needing fine focus, your best option is magnified live view.


Steve

12-10-2020, 04:49 PM   #8
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The Pentax-M is a fully manual lens right? If that is the case, I would suggest not using catch in focus. I focused a Pentax-A 50mm f/1.7 lens for years on manual. What I did was I got used to what the picture looked like, sort of 'trust your instincts'. After practising it actually got a lot more reliable than using confirmation.
12-10-2020, 06:38 PM   #9
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In days of old, before auto focus, I would just pre focus on a spot and wait for the subject to move into it. It worked good for me. I still do it that way today instead of relying on catch in focus.
12-11-2020, 12:11 PM   #10
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QuoteOriginally posted by ShutterPro Quote
This wouldnīt be an issue for me if I didnīt use "Catch-in-focus". The pics come out really blurry then. I used a test chart for front and back focus, finding out a front focus of about 6 cm (pretty hard for close-up and portrait shots, huh?), making the adjustment -10.
In the 'Catch-in-focus' mode, the shutter will trip as soon as the camera detects an in-focus condition. The camera's focus detection system and confirmation indicator are used for autofocus lenses and manual focus lenses. Unfortunately, the 'in-focus' condition is detected over a small range of focus distances, so the shutter may trip even if the lens is not focused perfectly.

Here is an article that describes the focus issue, and how to achieve more accurate focus with manual-focus lenses: Achieving Better Manual Focus with the Green Hexagon - PentaxForums.com

The article does not cover 'catch-in-focus' specifically, but the techniques would apply in general.

- Craig
12-11-2020, 12:51 PM   #11
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QuoteOriginally posted by automorphism Quote
The Pentax-M is a fully manual lens right?
It is manual focus, has automatic aperture actuation, but does not support automated aperture control.

FWIW...CiF is problematic due to overrun either of focus ring or subject movement.

Steve
12-11-2020, 04:24 PM   #12
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QuoteOriginally posted by stevebrot Quote
It is manual focus, has automatic aperture actuation, but does not support automated aperture control.

FWIW...CiF is problematic due to overrun either of focus ring or subject movement.

Steve
I think you are probably right. I just preferred the feel of doing it more manually, as it gave me more awareness of the focus ring.
12-12-2020, 07:37 AM   #13
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QuoteOriginally posted by automorphism Quote
The Pentax-M is a fully manual lens right? If that is the case, I would suggest not using catch in focus. I focused a Pentax-A 50mm f/1.7 lens for years on manual. What I did was I got used to what the picture looked like, sort of 'trust your instincts'. After practising it actually got a lot more reliable than using confirmation.
Yes, it is. But I love it noless because of that.

---------- Post added 12-12-20 at 07:39 AM ----------

QuoteOriginally posted by ramseybuckeye Quote
Are you in AF.S? Are you using a tripod?
I did, but it didnīt work that well too. But Iīm getting used to viewfinder focusing now. Fortunately...

---------- Post added 12-12-20 at 07:40 AM ----------

QuoteOriginally posted by c.a.m Quote
In the 'Catch-in-focus' mode, the shutter will trip as soon as the camera detects an in-focus condition. The camera's focus detection system and confirmation indicator are used for autofocus lenses and manual focus lenses. Unfortunately, the 'in-focus' condition is detected over a small range of focus distances, so the shutter may trip even if the lens is not focused perfectly.

Here is an article that describes the focus issue, and how to achieve more accurate focus with manual-focus lenses: Achieving Better Manual Focus with the Green Hexagon - PentaxForums.com

The article does not cover 'catch-in-focus' specifically, but the techniques would apply in general.

- Craig
Thanks Craig, now I think I understand the problem.
J.
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