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AF Calibration Issue
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Oct 31, 2018 17:01:42   #
stangro
 
I'm trying to calibrate my prime lens on my Nikon D850. A couple of my primes have the following issue:

If I de-focus my lens by rotating my focus ring to the left and then autofocus I get an in focus reading of -1 to +4 on my target scale. If I then de-focus my lens by rotating my focus ring to the right, I then get an autofocus reading of -4 to +2.

This has happened with two of the four lens I have attempted to calibrate, so far (numbers of course change between lens).

Has anyone else had this problem? Am I doing something incorrectly?

My cam is on a tripod, I'm using AF-S, no vibration reduction, in aperture priority, with widest f stop an a well lite subject.

BTW - this does not happen in Liveview.



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Oct 31, 2018 18:24:16   #
NCMtnMan
 
If I'm correct, your 850 has an auto fine focus option. Steve Perry's book on the Nikon focus system discusses this and how to use it. I purchased his book and have found it to be extremely helpful and more than worth the few dollars he charges.

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Oct 31, 2018 18:29:23   #
duffy021049
 
Watch this video by Steve Perry it give you what you need.
https://www.youtube.com/watch?v=5cHhrWF-pqM

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Oct 31, 2018 19:52:03   #
User ID (a regular here)
 
stangro wrote:
I'm trying to calibrate my prime lens on my Nikon D850. A couple of my primes have the following issue:

If I de-focus my lens by rotating my focus ring to the left and then autofocus I get an in focus reading of -1 to +4 on my target scale. If I then de-focus my lens by rotating my focus ring to the right, I then get an autofocus reading of -4 to +2.

This has happened with two of the four lens I have attempted to calibrate, so far (numbers of course change between lens).

Has anyone else had this problem? Am I doing something incorrectly?

My cam is on a tripod, I'm using AF-S, no vibration reduction, in aperture priority, with widest f stop an a well lite subject.

BTW - this does not happen in Liveview.
I'm trying to calibrate my prime lens on my Nikon ... (show quote)



Your situation is not unusual. SLR AF is only approximate.

Estimate the central zone of your results and set that as
the correction to minimize error. You can't count on fully
eliminating error given the mechanisms of SLR AF.

`

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Oct 31, 2018 20:12:27   #
Gene51 (a regular here)
 
stangro wrote:
I'm trying to calibrate my prime lens on my Nikon D850. A couple of my primes have the following issue:

If I de-focus my lens by rotating my focus ring to the left and then autofocus I get an in focus reading of -1 to +4 on my target scale. If I then de-focus my lens by rotating my focus ring to the right, I then get an autofocus reading of -4 to +2.

This has happened with two of the four lens I have attempted to calibrate, so far (numbers of course change between lens).

Has anyone else had this problem? Am I doing something incorrectly?

My cam is on a tripod, I'm using AF-S, no vibration reduction, in aperture priority, with widest f stop an a well lite subject.

BTW - this does not happen in Liveview.
I'm trying to calibrate my prime lens on my Nikon ... (show quote)


Don't bother trying to fine tune focus. Even on a D850. You do not have a focus issue - more than likely you are in spec. There is going to be some slack in the mechanism. It will not happen in live view because you are not relying on a mechanical system to perform autofocus. You are using the sensor and it's contrast evaluation, as opposed to mirrors, sensors, mechanical/electrical linkages, etc to perform AF, all of which have to be in 100% perfect alignment.

Also if you get your lens perfectly calibrated at one distance, there is no assurance that it will be focusing accurately at other distances, or that the lens will even focus at infinity. Something to consider.

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Oct 31, 2018 21:29:08   #
CO (a regular here)
 
Do you have the camera in single point autofocus? The vertical portion of your target is small. If the camera is focusing with multiple focus points active, it could be focusing on the target outside of the vertical portion. I think I found your target online. You would need to make sure the single focus point is landing on the vertical portion.


(Download)

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Oct 31, 2018 22:18:35   #
stangro
 
Yes, I found a link that describes the process and button sequence to push to have the camera auto correct the auto focus. It doesn't work 100% - you have to check the results and perhaps manually adjust the calibration number.

The url I found on this is: https://www.youtube.com/watch?v=m-kt7B0rNvM

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Oct 31, 2018 22:21:32   #
stangro
 
Yup, I'm on single point autofocus, and selected the narrow focus area option.

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Oct 31, 2018 22:42:39   #
stangro
 
I've seen Steve Perry's utube on this and have his book that further discusses this issue (thanks Steve). I will follow his suggested methodology. I just don't understand why manually defocusing in one direction from the other produces different results.

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Nov 1, 2018 07:28:04   #
abc1234
 
Gene51 wrote:
Don't bother trying to fine tune focus. Even on a D850. You do not have a focus issue - more than likely you are in spec. There is going to be some slack in the mechanism. It will not happen in live view because you are not relying on a mechanical system to perform autofocus. You are using the sensor and it's contrast evaluation, as opposed to mirrors, sensors, mechanical/electrical linkages, etc to perform AF, all of which have to be in 100% perfect alignment.

Also if you get your lens perfectly calibrated at one distance, there is no assurance that it will be focusing accurately at other distances, or that the lens will even focus at infinity. Something to consider.
Don't bother trying to fine tune focus. Even on a ... (show quote)


Having spent about 20 hours between SpyderCal and Reikan FoCal, I do not exactly welcome your advice Gene. You may very well be right so I hate to think I have been wasting my time. Neither of these devices plus a few others I have tried do not perform as easily or accurately as their manufacturers and proponents claim. Once I get done evaluating FoCal, I will post me findings here.

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Nov 1, 2018 10:41:34   #
RRS
 
stangro wrote:
I'm trying to calibrate my prime lens on my Nikon D850. A couple of my primes have the following issue:

If I de-focus my lens by rotating my focus ring to the left and then autofocus I get an in focus reading of -1 to +4 on my target scale. If I then de-focus my lens by rotating my focus ring to the right, I then get an autofocus reading of -4 to +2.

This has happened with two of the four lens I have attempted to calibrate, so far (numbers of course change between lens).

Has anyone else had this problem? Am I doing something incorrectly?

My cam is on a tripod, I'm using AF-S, no vibration reduction, in aperture priority, with widest f stop an a well lite subject.

BTW - this does not happen in Liveview.
I'm trying to calibrate my prime lens on my Nikon ... (show quote)


This might sound crazy but going over the info from "Lens-Align" there's some info that for defocusing Nikon you turn the lens to the left and Canon to the right. It has something supposedly to do on how they are designed. I know that there are folks out there that disagree on the whole thing but if you have a front or back issue when focusing something needs to be done. It seems to me that is the reason that the makers of the cameras now have that ability built in. If you only have one lens then you could send it back to Canon, Nikon or etc. but if the camera is adjusted and you have several lenses then you run the risk that all of your other lenses that are fine will now have a problem. If I sent both the camera and lens back I'd much prefer that they made the adjustment to the lens and not the body.

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Nov 1, 2018 10:46:39   #
abc1234
 
RRS wrote:
This might sound crazy but going over the info from "Lens-Align" there's some info that for defocusing Nikon you turn the lens to the left and Canon to the right. It has something supposedly to do on how they are designed. I know that there are folks out there that disagree on the whole thing but if you have a front or back issue when focusing something needs to be done. It seems to me that is the reason that the makers of the cameras now have that ability built in. If you only have one lens then you could send it back to Canon, Nikon or etc. but if the camera is adjusted and you have several lenses then you run the risk that all of your other lenses that are fine will now have a problem. If I sent both the camera and lens back I'd much prefer that they made the adjustment to the lens and not the body.
This might sound crazy but going over the info fro... (show quote)


What you might mean is that different manufacturers design their lens to focus to infinity by turning clockwise or counterclockwise. Gene raises the issue of hysteresis and that is the AF may give different results based upon whether you focus from near or far. That is probably the result of real-world design and manufacturing considerations.

As far as I know, the only lenses that you can adjust are some from Sigma and Tamron. Otherwise, you adjust the body. I hope some will clarify this.

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Nov 1, 2018 11:07:00   #
dsmeltz (a regular here)
 
stangro wrote:
I'm trying to calibrate my prime lens on my Nikon D850. A couple of my primes have the following issue:

If I de-focus my lens by rotating my focus ring to the left and then autofocus I get an in focus reading of -1 to +4 on my target scale. If I then de-focus my lens by rotating my focus ring to the right, I then get an autofocus reading of -4 to +2.

This has happened with two of the four lens I have attempted to calibrate, so far (numbers of course change between lens).

Has anyone else had this problem? Am I doing something incorrectly?

My cam is on a tripod, I'm using AF-S, no vibration reduction, in aperture priority, with widest f stop an a well lite subject.

BTW - this does not happen in Liveview.
I'm trying to calibrate my prime lens on my Nikon ... (show quote)



It is odd that you get different results when starting with far or close focus. But as a practical matter, you may want to just choose one and micro-adjust accordingly. I would always start from a distant focus since that is the situation I usually find (and put) myself in. I seldom take pictures of things moving away from me. If the focus is distant, then AF is moving in the same direction my subject is moving when seeking focus and will have less trouble locking.

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Nov 1, 2018 18:09:26   #
RRS
 
abc1234 wrote:
What you might mean is that different manufacturers design their lens to focus to infinity by turning clockwise or counterclockwise. Gene raises the issue of hysteresis and that is the AF may give different results based upon whether you focus from near or far. That is probably the result of real-world design and manufacturing considerations.

As far as I know, the only lenses that you can adjust are some from Sigma and Tamron. Otherwise, you adjust the body. I hope some will clarify this.
What you might mean is that different manufacturer... (show quote)


It is a misnomer, and you are right, you really don't change anything in the lens but only a fraction on the actual location of the sensor. Since the body and lens are not made as a unit and there is a tolerance (+/-) and the micro adjust for Canon or fine tune for Nikon is the manufactures way of letting the consumer make adjustments if they feel it's needed. I have 4 bodies and 6 lenses and have had to adjust every one and some 3 times if I use a 1.4 or 2X with the lens.

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