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05-22-2022, 01:57 AM   #1
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Pentax da 300mm F4 + pentax 1.4x TC AF fine adjustment help

Hello.

I was trying to calibrate my AF yesterday, looking at the pictures it looks like its front focusing but adjusting the settings doesnt change anything, at least i dont see any difference. My "tool" may not be most accurate, right now waiting for my order for right tool.

I attached some pictures where first should me 0 adjustment, +4 adjustment and -4 adjustment.


Thank you.

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05-22-2022, 03:10 AM   #2
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I would suggest do a search for the dot tune method, you’ll need a tripod and a tape measure along with your target.
05-22-2022, 04:07 AM   #3
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As for the method, dod you move the lens off focus between shots? The lens may be close enough for focus otherwise not to change.

But the bigger question, why do you feel the need to adjust in the first place.
05-22-2022, 05:52 AM   #4
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Did you take pictures with aperture wide open or with a smaller one? The depth of field is narrower (focus point easier to judge) when the f- number is smaller and that should be visible on the left side in the number scale 4-3-2-1-0-1-2-3-4 and adjoining measuring tape lines. A defocused lens would rather show 5-4-3-2x1-0-1-2 range sharp as an example, the focus being on the x roughly...
In your pics only the 4 is showing some unsharpness, making it hard to judge without rest of scale 5+ visible...
Judging the sharpness of top and bottom 3ís and 4ís is not very conclusive...

05-22-2022, 06:48 AM   #5
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1. Thank you, i will look into dot tune method.
2. Yes, i have cheap tripod (because i dont use it alot) and with heavy lens it isnt sturdy so there is a slight movement between each shot. As to why i think it needs adjusting is because when i shoot wildlife (mainly birds) i quite often find my shots are focused slightly forward. It may be user error but it's happening a bit too often.
3. I used wide open aperture F5.6 with TC on. Since my upload limit is full i uploaded pics to album with more points.

Link: https://www.pentaxforums.com/forums/members/131885-asynergy/albums/14387-af-adjustment/
05-22-2022, 07:11 AM   #6
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What is ACTUALLY being identified/read/calibrated/stored/adjusted with TWO AF lenses involved?


Might first try with only the lens mounted as a comparison.
05-22-2022, 07:12 AM   #7
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When you calibrate the AF/FA are you using APPLY ONE or APPLY ALL ?

05-22-2022, 07:32 AM   #8
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I assumed when i shoot with TC it's logical to adjust with it, i will try with lens only, ty.

I'm using apply one.
05-22-2022, 09:33 AM   #9
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Dot method gave me quite unconsitent results.

1. Around 10m : +8 -10 = -1
2.Around 40m : -7 +10 = +1.5
3. Around 40m but AF.S (idk if it even makes difference) : -9 +10 = 0.5
05-22-2022, 11:10 AM   #10
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Typically focus for a prime lens is calibrated at 25 * focal length which is 7.5m for a 300mm and 10.5m for a 420mm (300+1.4x) so your distances are a touch off possibly but Iíd expect more consistent results. Try doing several runs of dot tune refocusing after each one. If the tripod isnít stable use 2sec self timer and maybe add weights hanging down to give additional mass.
05-22-2022, 11:32 AM - 2 Likes   #11
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QuoteOriginally posted by Asynergy Quote
Dot method gave me quite unconsitent results.

1. Around 10m : +8 -10 = -1
2.Around 40m : -7 +10 = +1.5
3. Around 40m but AF.S (idk if it even makes difference) : -9 +10 = 0.5
I would leave it at zero and call it a day
05-22-2022, 11:57 AM   #12
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QuoteOriginally posted by Asynergy Quote
I assumed when i shoot with TC it's logical to adjust with it, i will try with lens only, ty.

I'm using apply one.
i did not think the APPLY ONE setting worked with a lens+ TC. How are you sure it is registering and remembering ?

---------- Post added 05-22-22 at 08:01 PM ----------

QuoteOriginally posted by Asynergy Quote
Dot method gave me quite unconsitent results.

1. Around 10m : +8 -10 = -1
2.Around 40m : -7 +10 = +1.5
3. Around 40m but AF.S (idk if it even makes difference) : -9 +10 = 0.5
AF/FA requires a consistent empirical approach. I would suggest you start with a good tripod. You need to do about 10 tests at each setting and take the average. Doing one test , and you are wasting your time.
05-23-2022, 05:39 PM - 1 Like   #13
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QuoteOriginally posted by pschlute Quote
i did not think the APPLY ONE setting worked with a lens+ TC. How are you sure it is registering and remembering ?

---------- Post added 05-22-22 at 08:01 PM ----------



AF/FA requires a consistent empirical approach. I would suggest you start with a good tripod. You need to do about 10 tests at each setting and take the average. Doing one test , and you are wasting your time.
Iím fairly certain that apply one works with the teleconverter as a unique entry separate from the lens without a tc.
3 Days Ago - 1 Like   #14
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QuoteOriginally posted by UncleVanya Quote
Iím fairly certain that apply one works with the teleconverter as a unique entry separate from the lens without a tc.
I found this text in the faq for the TC:
Question

Is it possible to register individually the AF fine adjustment with camera?

Individual registration will be possible by updating the corresponding firmware in the following models. (K-7, K-5, K-30, K-5 Ⅱ / Ⅱ s, K-50, K-500, K-3)
Recognizing the lens and DA AF rear convertor as another lens and it can register individually the AF fine adjustment.

HD PENTAX-DA AF REAR CONVERTER 1.4X AW | FAQ | Support | RICOH IMAGING (last question)
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