How does AF fine-tuning work for zoom lenses on a Nikon D850?
Asked 11/2/2019
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Nikon says the D850 can store autofocus fine-tune results for a lens type, but I’m unsure how that applies to zooms. If I calibrate a zoom lens at one focal length and aperture, will that correction also be accurate at other focal lengths and apertures?
For example, if I fine-tune a 16-35mm f/4 at 16mm and f/4, should I expect that same setting to work correctly at 35mm or when shooting stopped down?
Also, does the distance to the calibration target matter? If I calibrate at one subject distance, can focus still be off at other distances?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
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Unfortunately, as you've found, Nikon's in-body autofocus adjustment doesn't allow for different values at different focal lengths, apertures, or focus distances. Your suspicion is correct that those parameters can all change the adjustment required for perfect focus.
A common example is a phenomenon called focus shift: lenses with fast maximum apertures can experience changes in the plane of focus when stopping down from the widest apertures. Since the camera always focuses with the lens wide open and then stops down to take the picture (if set to a narrower aperture), lenses that exhibit this flaw may focus perfectly wide open but appear to need a slight adjustment when stopped down.
For in-body adjustments there's no ideal solution, but by calibrating the lens for the focal length and distance you'll be using most commonly, you can obtain an accurate calibration for those shots and hopefully be not too far off for the rest. It's worth mentioning that some third-party lens makers, notably Sigma and Tamron, sell docks that can be used to configure and calibrate their lenses, and those do allow independent adjustments at several different focus distances.
Originally by user91780. Source · Licensed CC BY-SA 4.0
user91780
6y ago
0
Generated from our catalog & community — verify before relying on it.
No. On the D850, in-body AF fine-tuning stores essentially one correction value per lens, not separate values for different focal lengths, apertures, or focus distances.
So with a zoom, a setting that improves focus at one focal length may not be perfect at another. The same applies to subject distance: some lenses can need slightly different correction close up versus farther away. Aperture can matter too, especially with lenses that show focus shift, because the camera focuses wide open and only stops down for the exposure.
In practice, there’s no single perfect correction if a lens varies across zoom range or distance. The usual approach is to calibrate for the focal length and distance that matter most to how you actually use the lens, or choose a compromise setting that works acceptably across the range.
If a lens is significantly inconsistent at different focal lengths or distances, that’s beyond what simple in-camera AF fine-tune can fully fix.
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