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11-16-2020, 07:49 AM   #1
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AF Fine Adjustment "Apply all" an exercise in futility (K-50)

I mostly shoot manual with my K-50, and I have had a lot of trouble with catch-in-focus and AF confirmation giving me blurry images. I decided to attempt to fix the problem by doing AF fine adjustment under "apply all" while using a manual focusing lens on a focus chart. The lens I chose was an old 50mm f2.0 k mount and all shots were taken wide open. The tripod was leveled and aligned precisely with the focusing chart, and I tried placing the chart and different distances to see if it affected results (it did not).

What I found was that the camera consistently front focuses rather severely. Moreoever, tweaking the AF fine adjustment settings had no discernable impact on the problem. As an experiment I tried dialing all the way to +10 and back down to -10, but the results were the same. Most of the time I did not use CIF, as I think other variables probably effect those results. Instead I dialed in focus until the green hexagon lit up, then snapped my pics using the self timer. The camera continued to front focus badly no matter what settings I used. This particular lens only works in manual mode with the green button programmed to TvShift for stop down metering, though I don't see why it would matter what mode I use for purposes of focus calibration. Of all my manual focus lenses it's the newest and in best condition, so it seems like the one to use.

I can only think of three explanations:

1. The fine adjustment range is too narrow - I know that in some cameras you can dial it to 20 in either direction, whereas the K-50 tops out at 10;

2. Whatever algorithm the camera uses to decide when to illuminate the green hexagon is unaffected by "apply all" AF fine adjustment;

3. There's some other variable I've failed to account for.

Appreciate any suggestions/feedback. I can get perfect focus in live view, but I would really like to not have to depend on live view so much when composing my shots, especially since I can't do CIF in live view.


Last edited by jimmypage; 11-16-2020 at 07:59 AM.
11-16-2020, 08:00 AM   #2
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Hello. The forum contains a description of the method for checking the camera. If the compensation is not enough, then you will probably have to visit the service. And you should also pay attention to the cleanliness of the mirror and the autofocus mine. I had two cases when the camera could not work properly due to dirt in the mine.
11-16-2020, 08:15 AM - 1 Like   #3
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QuoteOriginally posted by jimmypage Quote
Appreciate any suggestions/feedback. I can get perfect focus in live view, but I would really like to not have to depend on live view so much when composing my shots, especially since I can't do CIF in live view.
It sounds like you've been taking a fairly methodical approach to setting the AFFA. From what I understand, the AFFA range of +10 to -10 should be sufficient to accommodate most lenses. I have a couple of lenses that require settings near the extremes of the range.

One important thing I have discovered is that AFFA settings for a particular lens, and using the Green Hexagon, frequently depends on the direction of focus, i.e., focusing from far to near vs near to far.

I wonder if this article might be useful: Achieving Better Manual Focus with the Green Hexagon - PentaxForums.com

- Craig

Last edited by c.a.m; 11-16-2020 at 08:39 AM.
11-16-2020, 08:42 AM   #4
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Have considered the issue might be with the lens and not the camera? What if you try with other lenses?

11-16-2020, 08:43 AM   #5
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Welcome to the forum; nice to have you with us. I'm originally a Balti-moron. Now I'm just a moron.

If you don't have problems focusing with live view, but do have problems focusing manually through the viewfinder, I wonder if the diopter setting on your viewfinder needs to be adjusted to your eye.

The green hexagon is helpful, but not always foolproof. Sometimes there is a small range of lens focus settings that will illuminate the green hexagon. I found this video about the 'dot tune method' to be very informative and helpful.
11-16-2020, 09:11 AM   #6
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QuoteOriginally posted by jimmypage Quote
I mostly shoot manual with my K-50, and I have had a lot of trouble with catch-in-focus and AF confirmation giving me blurry images. I decided to attempt to fix the problem by doing AF fine adjustment under "apply all" while using a manual focusing lens on a focus chart. The lens I chose was an old 50mm f2.0 k mount and all shots were taken wide open. The tripod was leveled and aligned precisely with the focusing chart, and I tried placing the chart and different distances to see if it affected results (it did not).

What I found was that the camera consistently front focuses rather severely. Moreoever, tweaking the AF fine adjustment settings had no discernable impact on the problem. As an experiment I tried dialing all the way to +10 and back down to -10, but the results were the same. Most of the time I did not use CIF, as I think other variables probably effect those results. Instead I dialed in focus until the green hexagon lit up, then snapped my pics using the self timer. The camera continued to front focus badly no matter what settings I used. This particular lens only works in manual mode with the green button programmed to TvShift for stop down metering, though I don't see why it would matter what mode I use for purposes of focus calibration. Of all my manual focus lenses it's the newest and in best condition, so it seems like the one to use.

I can only think of three explanations:

1. The fine adjustment range is too narrow - I know that in some cameras you can dial it to 20 in either direction, whereas the K-50 tops out at 10;

2. Whatever algorithm the camera uses to decide when to illuminate the green hexagon is unaffected by "apply all" AF fine adjustment;

3. There's some other variable I've failed to account for.

Appreciate any suggestions/feedback. I can get perfect focus in live view, but I would really like to not have to depend on live view so much when composing my shots, especially since I can't do CIF in live view.
Perhaps this helps: https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/. As it is about AF I think you should use an AF lens because that kind of lens will interact with the camera. First you should find out if an AF lens shows the same problem, if it does not the problem lies with the lens. With a manual lens the camera can not front focus, because you operate the lens and not the camera. I used the testcams method and it solved the problem. If you fine tune the camera with an AF lens the manual lens profits from that.
11-16-2020, 09:25 AM   #7
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QuoteOriginally posted by AfterPentax Quote
First you should find out if an AF lens shows the same problem, if it does not the problem lies with the lens. With a manual lens the camera can not front focus, because you operate the lens and not the camera.
I think it's a good idea for the OP to compare their experiences in calibrating autofocus and manual focus lenses. It's important to validate the calibration procedure.

If the camera's Green Hexagon is used to indicate focus, then it is certainly possible to arrive at a front-focused or back-focused situation if the lens is not calibrated. The article linked in post #3 above discusses this aspect and gives several examples.

QuoteOriginally posted by AfterPentax Quote
If you fine tune the camera with an AF lens the manual lens profits from that.

Each lens, whether AF or MF, needs to be calibrated individually and independently. Would it be possible for you to give more detail of what you mean?

- Craig


Last edited by c.a.m; 11-16-2020 at 09:37 AM.
11-16-2020, 09:46 AM   #8
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I should have mentioned that I have calibrated two AF lenses successfully, one front focusing and the other backfocusing badly. It seems from reading other threads that the green hexagon can be triggered at different points depending on which direction you're focusing from, and that the sweet spot is somewhere in between the two points where it lights up. If that's true then it's effectively useless to me and I'm better off just using a magnifying eyecup and/split focusing screen. Using the AF system to do the work for me is a cute idea but perhaps too cumbersome in practice, and live view with focus peaking still works great.



---------- Post added 11-16-20 at 09:51 AM ----------

QuoteOriginally posted by AfterPentax Quote
Perhaps this helps: https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/. As it is about AF I think you should use an AF lens because that kind of lens will interact with the camera. First you should find out if an AF lens shows the same problem, if it does not the problem lies with the lens. With a manual lens the camera can not front focus, because you operate the lens and not the camera. I used the testcams method and it solved the problem. If you fine tune the camera with an AF lens the manual lens profits from that.
This sounds intriguing but what do you mean by "fine tune the camera?" I've fine tuned AF lenses but the settings are lens specific. I could pick a random AF lens and do "apply all" tuning but if it's the lens itself that's wonky I don't see how that would fix the problem. I do like the idea that this fundamentally a lens issue. I will try the same procedure with some other manual lenses and see if I get that same results.
11-16-2020, 11:41 AM   #9
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QuoteOriginally posted by jimmypage Quote
the sweet spot is somewhere in between the two points where it lights up. If that's true then it's effectively useless to me and I'm better off just using a magnifying eyecup and/split focusing screen. Using the AF system to do the work for me is a cute idea but perhaps too cumbersome in practice, and live view with focus peaking still works great.
Yes, the "sweet spot" for focus is somewhere in between the two illumination points. As described in the article linked in post #3 above, the trick is to calibrate the lens for one of the two illumination points, then focus consistently with that lens from far or from near. Finding the best AFFA setting does take some time, but I've found that the procedure is not overly onerous.

I would agree that other aids to determine proper focus -- such as a magnifying eyecup, special focusing screen, or live view -- can work well, although each comes with its own disadvantages or issues. When my camera is mounted on a tripod, I almost always use magnified Live View to achieve spot-on focus.

Interested to hear the results with your other MF lens(es).

- Craig
11-16-2020, 01:01 PM   #10
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QuoteOriginally posted by jimmypage Quote
It seems from reading other threads that the green hexagon can be triggered at different points depending on which direction you're focusing from, and that the sweet spot is somewhere in between the two points where it lights up. If that's true then it's effectively useless to me and I'm better off just using a magnifying eyecup and/split focusing screen. Using the AF system to do the work for me is a cute idea but perhaps too cumbersome in practice, and live view with focus peaking still works gre
A few points to take on board:

The green hexagon will give different results when focussed from the infinity or closest focus distance on the lens.You will find that an AF lens will have the same issues. PDAF is just not that accurate.

You would be better off using LV magnified 100%. This is the gold standard for manual focus lenses.

You mentioned earlier that you got the same results whether the camera was set to -10 or +10. This cannot be right and I am afraid shows an error on your part. When you have calibrated a manual focus lens and used the APPLY ALL setting you MUST make sure you exit the menu screen in the APPLY ALL mode. Otherwise no setting will be applied and I fear this is what is happening. The manual does not make this very clear so I do understand any confusion.

You must do about 10 tests at each setting and calibrate accordingly. A single test will not be sufficient. As I said earlier PDAF is just not that accurate.

It is quite normal for the PDAF system to resister a "in focus" shot at more than one position on one lens. You need to go with the majority.
11-16-2020, 01:27 PM   #11
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QuoteOriginally posted by jimmypage Quote
I mostly shoot manual with my K-50, and I have had a lot of trouble with catch-in-focus and AF confirmation giving me blurry images. I decided to attempt to fix the problem by doing AF fine adjustment under "apply all" while using a manual focusing lens on a focus chart. The lens I chose was an old 50mm f2.0 k mount and all shots were taken wide open. The tripod was leveled and aligned precisely with the focusing chart, and I tried placing the chart and different distances to see if it affected results (it did not).

What I found was that the camera consistently front focuses rather severely. Moreoever, tweaking the AF fine adjustment settings had no discernable impact on the problem. As an experiment I tried dialing all the way to +10 and back down to -10, but the results were the same. Most of the time I did not use CIF, as I think other variables probably effect those results. Instead I dialed in focus until the green hexagon lit up, then snapped my pics using the self timer. The camera continued to front focus badly no matter what settings I used. This particular lens only works in manual mode with the green button programmed to TvShift for stop down metering, though I don't see why it would matter what mode I use for purposes of focus calibration. Of all my manual focus lenses it's the newest and in best condition, so it seems like the one to use.

I can only think of three explanations:

1. The fine adjustment range is too narrow - I know that in some cameras you can dial it to 20 in either direction, whereas the K-50 tops out at 10;

2. Whatever algorithm the camera uses to decide when to illuminate the green hexagon is unaffected by "apply all" AF fine adjustment;

3. There's some other variable I've failed to account for.

Appreciate any suggestions/feedback. I can get perfect focus in live view, but I would really like to not have to depend on live view so much when composing my shots, especially since I can't do CIF in live view.
There are a few pointers based on my experience.

Often the wrong focus point is picked - especially common to pick up a small clump of grass in front of a bird on the ground. I've had perfectly focused pictures of dandelions with a blurry bird behind ;-).

It's better to tune the focus based on something at a similar distance to your normal usage, I find a fence taken at a narrow angle gives good results.

Adjust the dioptre setting in the viewfinder (I use mine without glasses although I need them for astigmatism at any distance & long sightedness) and trust your vision rather than the hexagon.
11-16-2020, 02:23 PM   #12
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QuoteOriginally posted by pschlute Quote

You mentioned earlier that you got the same results whether the camera was set to -10 or +10. This cannot be right and I am afraid shows an error on your part.
I may have mispoken about settings having no effect. It's just that the camera was front focused when set to either extreme. There may have been some marginal change, but it was front focusing badly at all times.

I like the video posted above about calibrating the green hexagon, rather using the green hexagon to calibrate the camera. Will give it a shot and report back.
11-16-2020, 02:52 PM   #13
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"Each lens, whether AF or MF, needs to be calibrated individually and independently. Would it be possible for you to give more detail of what you mean?" What I mean is that in the case of the OP he wants to "apply to all" so it would be easier to calibrate with an AF lens. If you use the dot tune method you can easily find the margin in which all lenses will be sharp when using AF. I did so and from then on manual lenses were easier to get into focus than before. I noticed and described in another thread that if I am manually focusing I need the red dot flashing and the moment the green hexagon flashes I must expose. Because the moment the green hexagon is on, most of my pictures were out of focus. After some correction with the dot tune method I can now manually focus and wait till the green hexagon is on and take the picture. That is the advantage if you want AF adjusting to apply to all. If you want to calibrate each lens seperately you can only store a limited number of lenses in memory. But you can not store information of older lenses, it only works on A lenses and later., lenses that can interact with the camera.

Last edited by Unregistered User; 11-16-2020 at 04:07 PM. Reason: additonal information added
11-16-2020, 03:37 PM   #14
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Just to be clear here for those unfamiliar with how the AF/FA system works........

APPLY ONE only sets adjustment for one specific lens. This can only be a lens which the camera can identify as unique...so K or M series lenses cannot be set this way.

APPLY ALL will apply an adjustment for any lens including manual focus lenses. The AF system will illuminate the green hexagon when it detects focus lock with a manual lens.

The AF/FA is not only for setting an adjustment number, but is also for telling the camera what to do.....ie if you set a APPLY ONE setting you need to exit the menu while in APPLY ONE or the setting will not be applied.

If you set an APPLY ALL setting (or leave it at 0 ) and exit the menu in that setting the APPLY ALL setting will be used for all lenses, even those that have been assigned an individual adjustment in APPLY ONE

If you exit the menu in the APPLY ONE setting, and you have mounted a lens either for which you have not set a APPLY ONE correction, or the lens is one for which the camera cannot recognise .(.ie a M or K series lens), the menu reverts to the APPLY ALL setting.
11-16-2020, 04:19 PM   #15
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QuoteOriginally posted by jimmypage Quote
I should have mentioned that I have calibrated two AF lenses successfully, one front focusing and the other backfocusing badly. It seems from reading other threads that the green hexagon can be triggered at different points depending on which direction you're focusing from, and that the sweet spot is somewhere in between the two points where it lights up. If that's true then it's effectively useless to me and I'm better off just using a magnifying eyecup and/split focusing screen. Using the AF system to do the work for me is a cute idea but perhaps too cumbersome in practice, and live view with focus peaking still works great.



---------- Post added 11-16-20 at 09:51 AM ----------

This sounds intriguing but what do you mean by "fine tune the camera?" I've fine tuned AF lenses but the settings are lens specific. I could pick a random AF lens and do "apply all" tuning but if it's the lens itself that's wonky I don't see how that would fix the problem. I do like the idea that this fundamentally a lens issue. I will try the same procedure with some other manual lenses and see if I get that same results.
Hi Jimmypage, I repeat again to make it clear, AF adjustment is not for manual focus lenses, but for autofocus lenses. Because you need a lens that can interact, that is, give information to, the camera. An mf-lens of K&M mount can not do that. So it is actually fine tuning the camera to work with a certain AF lens or all of your lenses. Read the message from pschlute, he explains it very well.
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