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12-08-2017, 04:19 PM   #1
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Focus calibration

Originally posted by Ascencio:
Thanks

playing more with the lens and not going to infinity or closest focus distance during calibration i was able to adjust it with the usb dock to work on my K-1.

my new question is i was hoping to be able to use it on my k-3 as a 50mm lens and focus is off.

can the focus sensors on my k-1 and k-3 be calibrated to be in sync so i dont have issues with this lens and future lenses. If so is the only place precision camera?

i had a zeiss 25 and 35 that im kind of regretting selling. should have stuck with manual focus.

QuoteOriginally posted by Adam:
QuoteOriginally posted by Ascencio:
Adam,

I just bought a Sigma 35mm 1.4 and wanted some advice before sending it back. It's focus is off i got it with the usb dock and tried to adjust it but still doest work very well. The first two distances i adjusted and seemed to work with the chart but once i got to the third distance it started to focus inconsistent front and back etc. What is confusing is it focus accurately in live view but not with the view finder. Does the same on my k-1 and k-3. I have a pentax 55 1.4. Any chance its the camera?

Erick
Hi Erick,

Focus adjustments only apply to viewfinder shooting, rather than live view. Live view will always be accurate because it uses trial and error rather than calculations to determine focus. Thus, the behavior you're describing seems perfectly normal. If the dock doesn't fully remedy the viewfinder focusing issues, I would just exchange the lens if possible.

12-08-2017, 04:21 PM   #2
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QuoteOriginally posted by Ascencio Quote
can the focus sensors on my k-1 and k-3 be calibrated to be in sync so i dont have issues with this lens and future lenses. If so is the only place precision camera?
It is normal for different bodies to require different adjustments, so this is not a service that's typically performed. You can send a lens in along with the camera if there's a problematic combo, though.

With Pentax-branded lenses this isn't an issue since you can save a specific focus adjustment preset for each lens.

Adam
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12-08-2017, 08:52 PM   #3
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I have this lens and a K3II and K1. I originally got it when I only had the K3II, and used the dock to assist with the calibration. When I got the K1, things seemed screwy. I used the dock to reset the lens to 0 adjustment at all intervals, and then used the in camera fine focus adjustment, and it seems to be working well. I'd give a shot at resetting the lens to 0 and see what you can do in the bodies.
11-06-2019, 12:25 PM   #4
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Hi.
I have recently been helping a friend with calibration issues with her Canon camera & lenses. Yet I have used Pentax DSLRs since they first came out, had more than six models ( currently a K-5 and a K-S1), and have NEVER encountered a single AF issue with any lens, Pentax or third-party. Have I just been lucky, or is it the fact that I set my AF point to a small area of screen?
mike

11-30-2019, 09:09 PM   #5
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QuoteOriginally posted by martin42mm Quote
Hi.
I have recently been helping a friend with calibration issues with her Canon camera & lenses. Yet I have used Pentax DSLRs since they first came out, had more than six models ( currently a K-5 and a K-S1), and have NEVER encountered a single AF issue with any lens, Pentax or third-party. Have I just been lucky, or is it the fact that I set my AF point to a small area of screen?
mike
Is she using multi-point and you are using single point? I find if I use multi-point, the camera if often grabbing something other than what I intended, so perhaps you are getting more hits since you're using spot and getting what you're after? And many other variables too, but that's a starting thought.
12-01-2019, 03:27 AM   #6
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Focus calibration

That is exactly what i asked when she mentioned the issue. It seems she uses a centre-weighted cluster of AF points, wheras I use a single one. However even with the change to a single one, the problem persisted. the camera is currently back with the dealer for investigation-I'l update when I know more.
12-01-2019, 06:37 AM   #7
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QuoteOriginally posted by martin42mm Quote
Have I just been lucky,
I suggest you have been lucky. While there will be a difference, depending on the scene, between multi points and single point any AF misalignment will affect them both. If you were to AF on a perfectly flat wall using both methods you would find the same error on both. single centre point should always be used for calibration.

My K1 requires +6/+10 adjustment on all my lenses, indicating to me that the problem is largely the AF module in the camera. Each lens behaves slightly differently, showing that it is the lens/camera combo that one is always adjusting, not just the camera.

As I always say when this subject comes up, PDAF is not 100% reliable. So you cannot use one test to determine if you need adjustment. You need to do at least 10 tests making the camera focus from both extremes of the range, and then make any AF/FA adjustment basis the majority result.
12-01-2019, 08:26 AM   #8
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QuoteOriginally posted by pschlute Quote
I suggest you have been lucky. While there will be a difference, depending on the scene, between multi points and single point any AF misalignment will affect them both. If you were to AF on a perfectly flat wall using both methods you would find the same error on both. single centre point should always be used for calibration.

My K1 requires +6/+10 adjustment on all my lenses, indicating to me that the problem is largely the AF module in the camera. Each lens behaves slightly differently, showing that it is the lens/camera combo that one is always adjusting, not just the camera.

As I always say when this subject comes up, PDAF is not 100% reliable. So you cannot use one test to determine if you need adjustment. You need to do at least 10 tests making the camera focus from both extremes of the range, and then make any AF/FA adjustment basis the majority result.
Personally I prefer manual focus unless it is imperative to freeze action under severe conditions, or where eyesight is becoming an issue..There are more arguments and problems from autofocus issues in both cameras and lenses than any problems that have ever arisen with manual focus.I have always thought it is a solution for a problem that rarely exists, and that there are too many compromises that have to be made to get it to work correctly, and swiftly. As someone who has stripped down many hundreds of modern lenses to repair them it horrifies me to see the mechanical compromises that are made in lens group location-you cannot locate a multi-element lens group with one or two plastic lugs.Try sitting on a one-legged or two-legged stool-it doesn't work. Add to that the huge clearances needed to reduce friction for the AF motors and the problem gets worse. All that computer design power is wasted because the actual lenses are not located squarely in the lens barrels! Having recently had to tighten an element locking ring that was perhaps 1/4 turn off fully locked you would not believe the effect that had on the sharpness of this pro lens , Compared to the slop in modern AF element group locations it was completely square to the element axis.

For these reasons I have hated AF ever since it was first introduced (and lens barrel construction quality has declined since then), but then I learned how to use manual focus using a plain ground-glass screen on a Zenit back in the 60's. Since few modern focus screens are not optimised for manual focus, I use a cut-down Canon screen which is an improvement on the standard one But I'm a bit of a Luddite when it comes to photography, preferring metal lenses for their general feel to the plastic that is often needed to aid fast AF in modern lenses. I also think the weight aids positive focus as does a decent helical system..

12-01-2019, 08:39 AM   #9
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QuoteOriginally posted by martin42mm Quote
Personally I prefer manual focus unless it is imperative to freeze action under severe conditions
I too am a big fan of manual focus. On a tripod I invariably use LV zoomed 100%.

For my dog portraits manual focus is just hopeless. I certainly need a well calibrated system for that.
12-29-2019, 08:31 PM   #10
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QuoteOriginally posted by martin42mm Quote
the actual lenses are not located squarely in the lens barrels!
I've noticed all sorts of movement in the barrels of a variety of lenses and wondered how close they could possibly be to their intended design.
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