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05-25-2013, 09:04 AM   #1
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AF Adjustment

I need some help with AF Fine Adjustment. I think I need to send my K-5 to Pentax for service.

I used a LensAlighn and several manual lenses to calibrate my K-5 autofocus. I set the focus switch to af.s and turn on catch in focus. Then I slowly focus on the LenAlighn target. The first picture below is with the fine AF adjustment set to zero, clearly front focusing. The second photograph is with the af adjustment set to -10, the maximum compensation for a front focus adjustment. This picture is better but the K-5 still shows a slight front focus.

I did this test with a few lenses - the same result.

At -10 there is no further adjustment for a auto focus lens that has some inherent front focus, front focus would just get worse. Before I did this test my DA*16-50 needed a +5 adjustment, now it would be -5. Most of my other auto focus lenses also needed a + adjustment - the Sigma 70-200 was also a plus adjustment.

It seems my camera's front focus issue is not the lenses but the Pentax K-5.

I plan to contact Pentax after the holiday and see if they can adjust the af on the K-5 so that manual lenses are zero.

I've read a lot about lenses that front focus on the forum. Could it be the K-5 that front focuses and the lenses are doing it correctly?

Has anyone else encountered this problem.

With the camera's auto focus fairly close (at minus 10) is the full plus to minus 10 still available for individual lenses?

If so - perhaps the -1- setting is close enough.

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05-25-2013, 09:21 AM   #2
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Front focus / back focus is not a lens issue or a camera issue. It is caused by small tolerances in the manufacture of both components. So if you have a camera that is +5 and a lens that is -5 then the differences cancel and you will declare that lens spot on. But take that same lens and put it on a different camera that is -5 and suddenly the lens is declared terrible because the net is -10.

QuoteOriginally posted by RockvilleBob Quote
I plan to contact Pentax after the holiday and see if they can adjust the af on the K-5 so that manual lenses are zero.
They may be able to adjust your camera to match ONE manual lens, but since all lenses potentially have different tolerance settings they may actually make your other lenses worse. The settings for newer lenses with ID chips can be set individually so each lens can be matched to your camera, but on manual lenses (unless they have an ID chip, and I'm not aware of any that do) you can only set the camera AF fine tuning to match one lens.

Also, be aware that on very fast lenses the AF confirmation light 'range' of confirmation is broader than the actual depth of focus and dead center might not be correct. Some have reported that using one edge or the other of the confirmation range works better. This might change with different lenses of course.
05-25-2013, 09:22 AM   #3
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Under what lighting? The K-5 has trouble focusing under some lighting conditions. Also I feel that CIF isn't perfect as it often takes the pics at the back or front of the "sharp" area, also it's possible that you (at least I do) moves the focus ring even slightly after the camera locks the focus, it's very hard to be exact. Did you try focusing the manual lenses in both directs to see if it varies with the direction you turn the ring?

As long as the adjustments are within +-10 I see no need to send it in, lenses and camerabodies will always vary when it comes to focus calibration, it's the desadvantage of phase detection. For all to be pretty much perfect the cameras and lenses would cost way too much to manufacture.
05-25-2013, 09:24 AM   #4
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AF adjustment is for AF lenses. If you try doing it with manual lenses, you're going to get unpredictable results due to the tolerance range where the AF considers things to be in focus. Also, if the photos above were shot with the K-5, you're not properly aligned with the target. Follow this guide:

Fixing Front and Back Focus - The Remedy - PentaxForums.com

BTW, if it turns out that your camera needs a global adjustment, there's also an option for that (see the screenshots on the page above).


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05-25-2013, 09:57 AM   #5
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Thanks for all your suggestions.

I did these indoors and will try the same technique in sunlight tomorrow. Regarding alignment of the LensAlighn my understanding is that f the small red dot behind the LensALIGHN BULL'S EYE is in the center, equally surrounded by white, the camera and the Lensalighn are aligned. I'll have to go back and re-read the directions when I set the rig up outside - I use two tripods.

I will also do the test again with multiple manual lenses. I take the pictures turning the focus ring both ways and turning very slowly. Doing this I have not noticed a difference between approaching focus from the rear or the front, the results for a given lens seem the same.

More light will help.
05-26-2013, 07:55 PM   #6
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While I've never tried to do any AF adjustment with manual lenses, this is the first time I've heard of anyone using catch in focus for calibration purposes. How can you be sure you are stopping the focus ring at exactly the right time? In my mind there is a possibility that you can still be turning the focus ring past the point when the camera fires.

Anyway, trying to answer one of your questions, I've had 2 K-5's in the past where the camera itself was back or front focusing (using AF lenses). I won't get into the long drawn out story, but will tell you that both times I sent the camera to CRIS where they did verify the AF was back or front focusing and were able to adjust it. They have a master lens that they use to do this to get the adjustment to spec. Both times the camera came back focusing perfectly - of course there were a couple lenses that did need a small bit of fine adjustment which is normal.
05-26-2013, 09:12 PM   #7
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You might find this old Pentax AF calibration guide has some useful tips. Eg they recommend lighting the target quite brightly to EV12 or more, setting to spot focus etc.



Also it's probably not a good idea to shoot your AF target with a light source behind it. Could throw out the AF or the AE metering.
05-27-2013, 03:31 AM   #8
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QuoteOriginally posted by stormtech Quote
While I've never tried to do any AF adjustment with manual lenses, this is the first time I've heard of anyone using catch in focus for calibration purposes. How can you be sure you are stopping the focus ring at exactly the right time? In my mind there is a possibility that you can still be turning the focus ring past the point when the camera fires.

Anyway, trying to answer one of your questions, I've had 2 K-5's in the past where the camera itself was back or front focusing (using AF lenses). I won't get into the long drawn out story, but will tell you that both times I sent the camera to CRIS where they did verify the AF was back or front focusing and were able to adjust it. They have a master lens that they use to do this to get the adjustment to spec. Both times the camera came back focusing perfectly - of course there were a couple lenses that did need a small bit of fine adjustment which is normal.
Thank you for the information Stan.
I need to do the focus test in daylight to confirm but I now feel confident sending the K-5 to Pentax if needed.
For catch in focus I turn the focus ring very slowly and do the test coming both from behind the target and then from in front of the target. The results, so far have been the same so I do feel CIF while turning the focus slow works.
However I did the test in poor light.

05-27-2013, 03:33 AM   #9
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QuoteOriginally posted by rawr Quote
You might find this old Pentax AF calibration guide has some useful tips. Eg they recommend lighting the target quite brightly to EV12 or more, setting to spot focus etc.



Also it's probably not a good idea to shoot your AF target with a light source behind it. Could throw out the AF or the AE metering.
This is really appreciated - thank you very much. My test was done in poor light so I will repeat this using the proceedure you posted.
05-31-2013, 11:26 AM   #10
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Doing the focus calibration in daylight proved much better. The adjustment I settled on for the K-5 auto-focus adjustment for all lenses was -1, the minimum correction for very slight front focusing using a 90mm f28 macro lens. The macro lens was not only very sharp at f2.8 (Panagor 90 f2.8) but the extended focus mechanism permitted me to make smaller focus adjustments approaching the 'in focus' point. I did both catch in focus, coming from both directions, and also just using manual focus using the green in focus signal/beep. Using the macro lens and slowly turning the focus I did not notice much difference between the methods of focus and the results.

I did get the shims from Pentax yesterday and tried a couple different shims settling on a .20mm shim which provided good results using the KatzEye screen. The shim supplied with the K-5 yielded a good amount of front focus using manual focus.

I enjoy manual focus. There is just a good feeling of satisfaction when you get a shot you really feel is spot on using manual focus. I also like it because it opens the door to many lenses at an affordable price. To supplement the DA 15mm Ltd., DA*16-50, Sigma 70-200 and Sigma 150-500 I have a bunch of prime manual focus "vintage" lenses for my K-5, lenses where I could not afford to replace with today's auto-focus versions

Thanks again for all the help I received - The Pentax forum is a terrific resource since there have always been Pentax users with far more experience than me to provide advice and the K-5 is a excellent camera. Between a great camera and a terrific, very responsive forum Pentax is a great system that will only get better as Ricoh's investments take fruit.

Pentax should pay Adam and other who contribute so much to the forum.
06-04-2013, 12:10 PM   #11
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QuoteOriginally posted by RockvilleBob Quote
...Before I did this test my DA*16-50 needed a +5 adjustment, now it would be -5. Most of my other auto focus lenses also needed a + adjustment - the Sigma 70-200 was also a plus adjustment.
...

With the camera's auto focus fairly close (at minus 10) is the full plus to minus 10 still available for individual lenses?
I'm not sure how I ended up in this thread. but anyway...

I don't know how helpful this will be for you at this stage, but, if I'm reading you correctly, the above quotes imply that you believe that in AF Fine Adjustment, Apply All and Apply One work together i.e. they have a cumulative effect.

This is not the case. You can select one or the other. If Apply One is selected, the camera will use the setting previously set for the particular lens mounted. The Apply All value is not in the equation. If you select Apply All, then the same value will be used for any lens, and the Apply One value has no effect.

Also, you it may be useful for you to know that using PK Tether, you can enter Debug Mode on the K5, and then change the zero point of the AF Adjustment, so that zero is in effect, say, -2, or whatever. This, of course, is useful if you have a lens that needs more than the plus/minus 10 adjustment normally available. However, be aware that using this technique, you are limiting the range of adjustment available at the OTHER end of the scale, which may be a problem if you have a lens that requires extreme adjustment in the opposite direction of th elens you're trying to adjust in the first place.
06-04-2013, 02:32 PM   #12
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QuoteOriginally posted by bxf Quote
I'm not sure how I ended up in this thread. but anyway...

I don't know how helpful this will be for you at this stage, but, if I'm reading you correctly, the above quotes imply that you believe that in AF Fine Adjustment, Apply All and Apply One work together i.e. they have a cumulative effect.

This is not the case. You can select one or the other. If Apply One is selected, the camera will use the setting previously set for the particular lens mounted. The Apply All value is not in the equation. If you select Apply All, then the same value will be used for any lens, and the Apply One value has no effect.

Also, you it may be useful for you to know that using PK Tether, you can enter Debug Mode on the K5, and then change the zero point of the AF Adjustment, so that zero is in effect, say, -2, or whatever. This, of course, is useful if you have a lens that needs more than the plus/minus 10 adjustment normally available. However, be aware that using this technique, you are limiting the range of adjustment available at the OTHER end of the scale, which may be a problem if you have a lens that requires extreme adjustment in the opposite direction of th elens you're trying to adjust in the first place.
Yes you hit what I thought right on the money!! Now I need to go back to the drawing board again. Since y final adjustment to af for what I thought was an inherent camera issue is -1 then I probably need to just reset it to zero.

In my mind combining the "Apply All" and "Apply One" makes more sense but I am not a camera guru. Time to reread the manual on AF adjustment again.

Thank you for taking the time to point this out to me and thanks for finding this thread!
06-06-2013, 09:51 AM   #13
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Response from Pentax - confirms adjustments are not cumulative.

Thank you for contacting PENTAX. The two Auto Focus Fine Adjustment values are not cumulative, they are mutually exclusive. Also, the Auto Focus Fine Adjustment feature is intended for use with autofocus lenses, and will most likely have no effect when a manual focus lens (i.e. a lens without a lens ID chip) is mounted on the camera. If you are getting consistently mis-focused results when using manual focus lenses, check to see if the in-focus beep in the camera is enabled in the Set-up Menu. If it is, are you manually focusing using the beep as an in-focus indicator and does the in-focus indication of good focus correspond with what you are seeing through the viewfinder. I.E. is the in-focus indicator beep a good indicator of accurate focus in the camera? If the camera indicates good focus and the view through the viewfinder does not show the subject to be sharp, the diopter on the camera may need to be adjusted. The best way to do this is by using an autofocus lens, letting the camera achieve sharp focus, and then adjusting the diopter to the sharpest view through the viewfinder. If you are in need of further assistance, please respond to this email or call our technical support center at 800-877-0155.
06-06-2013, 10:22 AM   #14
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In my experiments it turned out that the focus indicators (small red box and the beep) most certainly depend on the AF Fine adjustment values. I did that on K100D via Debug menu with 50mm Pentax-A and M42 lenses.
06-06-2013, 03:42 PM   #15
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I will need to experiment a little. Setting the "Apply All" to 0 when using my auto-focus lenses for which I calibrated AF Fine Adjustments for already. When I use Manual lenses I will probably use small minus numbers (-1, -2) to see if it improves manual focus in my opinion. I will start with macro lenses since I think I will be able to see the variations more easily.
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