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by Tim Zurowski on Fri Nov 10, 2017 12:59 pm
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Tim Zurowski
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I just purchased a Nikon 200-500 lens and LOVE IT! Now I want to fine tune it to my D500, but I have never owned or fine tuned a telephoto zoom lens before this. It will be mostly used between 350mm and 500mm. I realize I can only tune it to one focal length. Would you do it at 500mm, 400mm, 300mm? I am inclined to do it at 400mm unless someone can say otherwise. 
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Tim Zurowski
www.timzphotography.com
 

by E.J. Peiker on Fri Nov 10, 2017 1:45 pm
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E.J. Peiker
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Definitely do it at 500mm. The longer the focal length, the more critical focus is and the more any errors will be amplified so you want to calibrate it at the most critical for focus point. This is one area where Canon beats Nikon by allowing you to calibrate the lens at minimum and maximum focal length and Sigma/ Tamron beats Nikon/Canon by allowing you to calibrate the lens at 4 focal lengths and 4 shooting distances for a 16 point matrix.
 

by Tim Zurowski on Fri Nov 10, 2017 2:00 pm
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Tim Zurowski
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Thanks EJ . . . . . I'll do it at 500mm then. I usually run the test three times and if it comes close each time then select the best point based on those results. For this lens, in two tests came it out at +6 and one at +7, so I set it at +6. Interesting because this lens was every bit as sharp (to my eyes) as my finely tuned 500 f4 VR, and it hadn't even been tuned yet. 
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Tim Zurowski
www.timzphotography.com
 

by E.J. Peiker on Fri Nov 10, 2017 3:15 pm
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When I get a value in between two like your +6 and +7 on a telephoto for primarily wildlife use I go for the slightly backfocused value because I almost always want more DOF behind where I am focusing than in front. So I would set it to +7 in that case.
 

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