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by Karl Egressy on Sat Nov 30, 2019 7:56 am
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I dropped the extender inside of the house from about three feet to the carpeted floor.
The caps were on.
To be on the safe side, I decided to redo the  micro-adjustment on two lenses I use it on for time to time.
To my surprise the micro-adjustment value has changed.
On the D850 500 f 5.6 PF +1.4x III it moved from 0 to -6.
On the D500 f300 f 4.0 PF -1.4x III it moved from +3 to 0.
What could have caused this shift?
Has something moved slightly inside of the extender?
Thanks. 
 

by Craig Browne on Sat Nov 30, 2019 10:05 am
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Hi Karl. Maybe it is just a temperature difference since the last time you adjusted it.
 

by SantaFeJoe on Sat Nov 30, 2019 12:07 pm
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Although the drop may have affected it, Craig could be right. I know that some people recalibrate AFFT when they go on safari. I have read that here and other places. Here’s a link to an article on the subject:

https://support.fo-cal.co.uk/article/28-how-often-should-i-check-or-calibrate-my-camera-lens-auto-focus

On page 2 of this thread, rnclark wrote about checking AFFT in the Serengeti due to temperature changes:

https://www.naturescapes.net/forums/viewtopic.php?f=57&t=252957&start=20

Joe
Learn the rules like a pro, so you can break them like an artist.  -Pablo Picasso
 

by E.J. Peiker on Sat Nov 30, 2019 1:38 pm
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If you could give a little more detail on what method you use to calibrate and if anything has changed, including how you review the calibration images, perhaps I can help.
 

by Karl Egressy on Sat Nov 30, 2019 2:10 pm
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With the D500 and D850 cameras I can use a method I saw posted, that is, to set it to live view, defocus, and focus and push two buttons simultaneously
that are the Movie-record button and the AF-mode button.
The target is a fine detail print mounted on the wall, 5" high.
The middle of the lens is set to 5' from the floor.
Perfect or near perfect perpendicular situation is achieved.
I take 12 shots, leave out the lowest and the highest (weighted average) and divide the sum by the number of remaining shots (10).
Distance winter time is 11.5m.(indoors) summer time 25 times of the focal length.
I made a comparison summer time with the distance variation.
500+1.5x 700 mm outdoors I used 17.0 m indoors the available 11.5 m and the results were identical.
It made me wonder if the 25 times minimum distance is mandatory.
Thanks.
 

by E.J. Peiker on Mon Dec 02, 2019 8:55 am
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Ah, the Nikon built in method of fine tuning that is almost guaranteed to give you less sharp pictures than doing nothing... ;) Perhaps a bit hyperbolic but not too far off. If you do the Nikon automated AFFT 10 times in a row you are likely to get 10 different answers. Your method though is about as good as you are going to get using that method.

As for distance, unless your most common shooting distance is shorter than the 25x recommendation, I would not change from that.

Not sure I understand the summer time references but I get the general gist ;)
 

by DChan on Mon Dec 02, 2019 11:44 am
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E.J. Peiker wrote:
Ah, the Nikon built in method of fine tuning that is almost guaranteed to give you less sharp pictures than doing nothing... ;)  Perhaps a bit hyperbolic but not too far off.  If you do the Nikon automated AFFT 10 times in a row you are likely to get 10 different answers.  Your method though is about as good as you are going to get using that method.[snip]


Which is also what you suggested back then when you tested that auto AFFT, if I remember correctly.
 

by E.J. Peiker on Mon Dec 02, 2019 11:47 am
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DChan wrote:
E.J. Peiker wrote:
Ah, the Nikon built in method of fine tuning that is almost guaranteed to give you less sharp pictures than doing nothing... ;)  Perhaps a bit hyperbolic but not too far off.  If you do the Nikon automated AFFT 10 times in a row you are likely to get 10 different answers.  Your method though is about as good as you are going to get using that method.[snip]


Which is also what you suggested back then when you tested that auto AFFT, if I remember correctly.

Yes but it is much more variable and less repeatable than doing it with a physical alignment tool and tethering the camera to a large screen and adjusting that way.
 

by Karl Egressy on Mon Dec 02, 2019 8:08 pm
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Most of the time the variation is very narrow and the sample size of 10 Is very generous I think.
Today I repeated the test on both camera/lens mentioned and got within one number different on one and two numbers different on the other.
I used a SpyderLenscal for the test. I'm not liking it as at the end I have to rely on my vision to make a judgement and my vision is not the greatest.
 

by DChan on Mon Dec 02, 2019 10:10 pm
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Questions:

1. ) If I repeat the test with various target distances, will I get different result for each distance?
2.)  If the results will not be the same, how far apart would they be?
 

by Karl Egressy on Tue Dec 03, 2019 4:30 am
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I mentioned before that I tested the affect of the distance variation before and I found not much if any, difference between the result.
If I have the chance like summertime when the temperature is decent and not minus eight like right now, I maintain the 25 times of the lens focus doing it outdoors.
 

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