Problems with AF fine tuning

spiralcity · 08-24-2022, 08:31 AM

Hi all,
I'm hoping I could get a few opinions on the AF Fine Adjustment. I have been tinkering around now for about 2 hours and my eyes are going a bit wonky. From my perspective the lens looked like it was a bit forward in the focusing, so I went -1. That didn't seem to be correct, so the long process started. I keep going back to 0 and I seem to be happiest there. It seems to my eyes that perhaps no correction is need. I could be wrong because my eyes are shot from 2 hours of this process.

A little help?

Below is an image with no correction. What are your opinions?
ƒ/7.1 - 1/125

Pete R · 08-24-2022, 08:36 AM - **1 Like**

I sympathise. I usually do it for a while, go cross-eyed and give up.
In this picture, I think the nearer "1" is sharper than the further "1", so yes, a little front-focussed.

kypfer · 08-24-2022, 08:48 AM - **1 Like**

With this sort of test I find it useful to make a few "giant" steps, +/- 5 or 10, just to see how far that sort of adjustment takes me on the scale, before finally settling down to the nitty-gritty of the job.
I also find it useful to double check by setting the lens to closest focus and letting the camera re-focus, then set the lens to infinity and repeat the exercise.
This can show up any slack or leeway in the focussing, so's you know that whether you're focussing from distance to close-up or vice versa that the camera is settling at the same spot

spiralcity · 08-24-2022, 10:06 AM

I'm thinking I found the spot. Please let me know what you all think.

Below is minus 5 and minus 6. I am leaning towards minus 5. All opinions are greatly appreciated.

MINUS 5

MINUS 6

**cpk** · 08-24-2022, 10:36 AM - **2 Likes**

If your aperture is set to f7.1, depth of field is going to skew your results. Your lens should be wide open or, at most, one stop down.

dlhawes · 08-24-2022, 11:13 AM

I hate those setups - the fuzzy stuff makes me crazy. I go outside and find a nice long fence and focus on a specific spot on the top of the railing, using a marker if necessary to make such a spot, take up a position at an angle thereto (it doesn't need to be 45 degrees, I prefer a more acute angle) and shoot from there. Then I use a photo viewer on the computer to blow up the pictures so I can see where the least-out-of-focus area is, and adjust to that.

As to that, most people try to find the spot that's in focus. I think that's the wrong approach. I look for areas on either side of the spot to find the edge or margin of the least-out-of-focus area, establishing two boundaries on either side of the most-in-focus-area. Then I make the adjustment to the center of the two boundaries.

Fogel70 · 08-24-2022, 01:06 PM - **2 Likes**

Another thing to consider is that AF adjustment done at close focus may not always be the same as needed for longer distances.
So after doing these adjustments the AF should be verified on other distances as well.

**Apet-Sure** · 08-24-2022, 01:08 PM - **1 Like**

Second vote for shooting these shots with the aperture wide open. You can also try the dot-tune method of AF fine adjustment, found on youtube.

---------- Post added 08-24-22 at 04:14 PM ----------

Originally posted by Fogel70

Another thing to consider is that AF adjustment done at close focus may not always be the same as needed for longer distances.So after doing these adjustments the AF should be verified on other distances as well.

What's the rule of thumb for AF adjustment focus distance - 20X the lens focal length? For a 50mm lens set the chart 1000mm (1 meter) away. Others may recommend different multiplication factors.

kypfer · 08-24-2022, 03:15 PM - **1 Like**

Originally posted by Apet-Sure

What's the rule of thumb for AF adjustment focus distance - 20X the lens focal length?

Pentax themselves quote 30-40x - 2m for a 50mm lens … see How to optimize focusing accuracy with large-aperture lenses / explore | RICOH IMAGING

spiralcity · 08-24-2022, 05:33 PM - **1 Like**

Thanks everyone. I am going back to the drawing board and doing this wide open.

Sandy Hancock · 08-25-2022, 04:26 AM

Thread moved to "Troubleshooting" sub-forum.

spiralcity · 10-01-2022, 05:41 PM - **1 Like**

I have been blocked out of the forum for some time. I discovered my firewall was blocking the server number. I just figured it out and I am back.

I reshot the scale wide open, and the results are the same. I used the lens at my setting of minus 5, and everything looks pretty good. Thanks all for the help and support, it's appreciated.

08-24-2022, 08:31 AM	#1
spiralcity Senior Member Join Date: Oct 2008 Location: Chicago,IL. U.S.A Posts: 147	Problems with AF fine tuning Hi all, I'm hoping I could get a few opinions on the AF Fine Adjustment. I have been tinkering around now for about 2 hours and my eyes are going a bit wonky. From my perspective the lens looked like it was a bit forward in the focusing, so I went -1. That didn't seem to be correct, so the long process started. I keep going back to 0 and I seem to be happiest there. It seems to my eyes that perhaps no correction is need. I could be wrong because my eyes are shot from 2 hours of this process. A little help? Below is an image with no correction. What are your opinions? ƒ/7.1 - 1/125

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08-24-2022, 08:36 AM - 1 Like	#2
Pete R Forum Member Join Date: Jul 2021 Location: Hampshire, UK Posts: 53	I sympathise. I usually do it for a while, go cross-eyed and give up. In this picture, I think the nearer "1" is sharper than the further "1", so yes, a little front-focussed.

08-24-2022, 08:48 AM - 1 Like	#3
kypfer Pentaxian Join Date: Jan 2018 Location: Jersey C.I. Posts: 3,596	With this sort of test I find it useful to make a few "giant" steps, +/- 5 or 10, just to see how far that sort of adjustment takes me on the scale, before finally settling down to the nitty-gritty of the job. I also find it useful to double check by setting the lens to closest focus and letting the camera re-focus, then set the lens to infinity and repeat the exercise. This can show up any slack or leeway in the focussing, so's you know that whether you're focussing from distance to close-up or vice versa that the camera is settling at the same spot

08-24-2022, 10:06 AM	#4
spiralcity Senior Member Join Date: Oct 2008 Location: Chicago,IL. U.S.A Posts: 147 Original Poster	I'm thinking I found the spot. Please let me know what you all think. Below is minus 5 and minus 6. I am leaning towards minus 5. All opinions are greatly appreciated. MINUS 5 MINUS 6

08-24-2022, 10:36 AM - 2 Likes	#5
cpk Site Supporter Join Date: Feb 2010 Location: Montreal Posts: 640	If your aperture is set to f7.1, depth of field is going to skew your results. Your lens should be wide open or, at most, one stop down.

08-24-2022, 11:13 AM	#6
dlhawes Guest	I hate those setups - the fuzzy stuff makes me crazy. I go outside and find a nice long fence and focus on a specific spot on the top of the railing, using a marker if necessary to make such a spot, take up a position at an angle thereto (it doesn't need to be 45 degrees, I prefer a more acute angle) and shoot from there. Then I use a photo viewer on the computer to blow up the pictures so I can see where the least-out-of-focus area is, and adjust to that. As to that, most people try to find the spot that's in focus. I think that's the wrong approach. I look for areas on either side of the spot to find the edge or margin of the least-out-of-focus area, establishing two boundaries on either side of the most-in-focus-area. Then I make the adjustment to the center of the two boundaries.

08-24-2022, 01:06 PM - 2 Likes	#7
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 3,062	Another thing to consider is that AF adjustment done at close focus may not always be the same as needed for longer distances. So after doing these adjustments the AF should be verified on other distances as well.

08-24-2022, 01:08 PM - 1 Like	#8
Apet-Sure Site Supporter Join Date: Dec 2015 Location: Goldsboro North Carolina Photos: Gallery \| Albums Posts: 2,872	Second vote for shooting these shots with the aperture wide open. You can also try the dot-tune method of AF fine adjustment, found on youtube. ---------- Post added 08-24-22 at 04:14 PM ---------- Originally posted by Fogel70 Another thing to consider is that AF adjustment done at close focus may not always be the same as needed for longer distances.So after doing these adjustments the AF should be verified on other distances as well. What's the rule of thumb for AF adjustment focus distance - 20X the lens focal length? For a 50mm lens set the chart 1000mm (1 meter) away. Others may recommend different multiplication factors.

08-24-2022, 03:15 PM - 1 Like	#9
kypfer Pentaxian Join Date: Jan 2018 Location: Jersey C.I. Posts: 3,596	Originally posted by Apet-Sure What's the rule of thumb for AF adjustment focus distance - 20X the lens focal length? Pentax themselves quote 30-40x - 2m for a 50mm lens … see How to optimize focusing accuracy with large-aperture lenses / explore \| RICOH IMAGING

08-24-2022, 05:33 PM - 1 Like	#10
spiralcity Senior Member Join Date: Oct 2008 Location: Chicago,IL. U.S.A Posts: 147 Original Poster	Thanks everyone. I am going back to the drawing board and doing this wide open.

08-25-2022, 04:26 AM	#11
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,275	Thread moved to "Troubleshooting" sub-forum.

10-01-2022, 05:41 PM - 1 Like	#12
spiralcity Senior Member Join Date: Oct 2008 Location: Chicago,IL. U.S.A Posts: 147 Original Poster	I have been blocked out of the forum for some time. I discovered my firewall was blocking the server number. I just figured it out and I am back. I reshot the scale wide open, and the results are the same. I used the lens at my setting of minus 5, and everything looks pretty good. Thanks all for the help and support, it's appreciated.