Nikkor Z 28-400mm f/4-8 VR Parfocal Analysis
- Ed Dozier
- Apr 25
- 2 min read
A ‘parfocal’ lens is a lens that doesn’t change focus as you zoom it. I have performed a very detailed analysis of this lens at focal lengths ranging from 400mm down to 50mm. I did a much less formal analysis all the way down to 28mm.
I will show you crops of photographs ranging from a distance of 6 feet out to 24 feet at various focal lengths to evaluate how focus is maintained. In each test, I would focus the lens at 400mm, and then take photos at 400mm, 200mm, 105mm, and 50mm without re-focusing at the other focal lengths. Minimum focus distance of this lens is a bit under 4 feet at 400mm.
I used a “Siemens Star” as the focus target. This subject is really excellent for showing the quality of focus. I used the Nikon Z8 camera for all testing, which was mounted on a tripod. I take the photos using a wired remote release to eliminate any vibrations.
As an aside, I have done an overall analysis of this lens here.This article is meant to provide some proof about the claims that I made in that overall analysis article.
400mm, 6 feet, Siemens Star. Set focus here.
200mm, 6 feet, Siemens Star: NO re-focus
105mm, 6 feet, Siemens Star: NO re-focus
50mm, 6 feet, Siemens Star: NO re-focus
400mm, 24 feet, Siemens Star. Set focus here.
200mm, 24 feet, Siemens Star NO re-focus
105mm, 24 feet, Siemens Star NO re-focus
50mm, 24 feet, Siemens Star NO re-focus
The Siemens target is really, really small in the frame at this distance for the 50mm focal length. Any sharpness loss here is due to the small target becoming insignificant in the overall frame.
Full frame of 50mm at 24 feet. Target is tiny.
Summary
Focus remained unchanged as I zoomed this lens, making it essentially parfocal. I stopped tests at focal lengths below 50mm, because the target Siemens Star was too small in the field of view. This Nikkor Z 28-400mm f/4-8 VR lens has an enormous zoom range of 14.3X.
In case you were wondering, yes, it stays in focus all the way down to 28mm. I did separate testing outdoors of a tree at 400 feet, and the branches were sharp at 28mm after focusing at 400mm. The 28mm aperture was f/4, while the 400mm aperture was f/8.
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Could it be that it's electronically compensated through focus adjustment rather than the lens being optically parfocal? It's often hard to tell with mirrorless lenses, since they are almost always focus-by-wire.