Does zooming a lens change focus on Nikon 18-55mm and 55-200mm lenses?
Asked 4/9/2011
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When I manually focus on my Nikon D60, I sometimes zoom in, set focus, then zoom back out to the framing I want. Will changing focal length also change the focus? I use the Nikon 18-55mm and 55-200mm kit lenses.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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It's not supposed to, but usually does.
The basic difference between a "varifocal" lens and a "zoom" is that a zoom stays in focus as the focal length changes. That's typically done by moving different lens elements simultaneously. The problem is that it's (at least normally) done mechanically, so manufacturing tolerances and wear in the lens prevents it from working quite perfectly in most cases.
There have been a few lenses that were poorly designed (at least in this respect) so the changes in focus were consistent, but in most cases it's more about mechanical tolerances, so it's mostly specific to a particular lens, not a design in general.
Originally by user603. Source · Licensed CC BY-SA 4.0
user603
15y ago
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Generated from our catalog & community — verify before relying on it.
Usually yes. In still-photography zoom lenses, changing focal length often shifts focus, so if you zoom in to focus and then zoom out, the image may no longer be perfectly focused.
A lens that stays in focus while zooming is called parfocal. That behavior is more common in video/broadcast lenses. Many still-photo zooms are effectively varifocal, meaning focus changes as you zoom and you should refocus after changing focal length.
Even lenses designed to hold focus can vary because of mechanical tolerances or wear, so the result may depend on the specific lens copy.
For your Nikon 18-55mm and 55-200mm, it’s safest to assume zooming can change focus. Compose at the focal length you actually want, then focus there.
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