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by hcarl on Tue Jan 05, 2021 9:24 pm
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If you do fine  tuning of a lens at 20 ft. Will it be the same at 60-100 ft.?
 

by ADKShooter on Wed Jan 06, 2021 5:42 pm
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Somewhere I learned that you move the decimal point of your length lens two places to the left and multiply by approximately 8 feet to get the correct distance to fine tune any specific length lens. For example for a 500mm lens the correct distance for fine tuning would be 5 x 8 = 40 feet. I'm not sure what to do in the case of a zoom lens but I would almost (almost) bet to set it to the longest length. For a prime lens my above formula seems to work well for me, but someone else who is more technically aware may want to chime in.
 

by hcarl on Wed Jan 06, 2021 6:56 pm
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ADKShooter wrote:
Somewhere I learned that you move the decimal point of your length lens two places to the left and multiply by approximately 8 feet to get the correct distance to fine tune any specific length lens.  For example for a 500mm lens the correct distance for fine tuning would be 5 x 8 = 40 feet.  I'm not sure what to do in the case of a zoom lens but I would almost (almost) bet to set it to the longest length.  For a prime lens my above formula seems to work well for me, but someone else who is more technically aware may want to chime in.



Thanks for the advice. It is a 500mm lens that I am going to fine tune to go along with my D810 so will give it a go.  Hcarl
 

by Joel Eade on Thu Jan 07, 2021 6:42 am
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hcarl wrote:
If you do fine  tuning of a lens at 20 ft. Will it be the same at 60-100 ft.?



Depends on the lens.

I recall that Canon recommends using a distance 25 times the focal length for setting the AF microadjustment of prime lenses.

Some Canon bodies will allow two separate AFMA values for zoom lenses so you can enter one for shortest and one for the longest focal length. 

Otherwise I think the recommendation for zoom lenses is to use the longest focal length.
 

by E.J. Peiker on Thu Jan 07, 2021 5:03 pm
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In most cases you won't find much difference between 20 feet and 50 feet but on some lenses, especially zooms it can make a difference. I would recommend 25 times the focal length so a 500mm lens would be calibrated at 12.5 meters. I would consider 10 meters the minimum.
 

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