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2024-03-18 20:23:14
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Varifocus vs Parfocal Zoom (Stills and Video Usage)

In my Varifocal Behavior page in my review of the Sigma 120-300mm f/2.8 DG OS HSM , I noted the following in reference to the behavior when the focal length is changed (“zoomed”):

  • A varifocal lens changes its focus when the focal length is changed and so must be refocused.
  • A parfocal zoom lense maintains focus when the focal length is changed.

Richard J writes:

Thank you for giving me this information that honestly I have been trying to find out for years. Mostly in regards to video cameras.

I have asked so many salesmen specifically about this behavior as we do a lot of on stage filming where parfocal is an asset, and only ever get blank stares back.

The question is, is their any way that I can easily identify if the lens is a varifocal or a parfocal? I never see it readily published and sales people are clueless. You are the first person I have read who has mentioned it.

DIGLLOYD: the vast majority of today’s “zoom” lenses are in fact varifocal lenses. Manufacturers simply skip the parfocal idea entirely since it demands high optical efforts not necessary or appropriate for most shooters.

Some of these so-called “zooms” shift focus only a little in when the focal length is changed, but that is usually too much even for sharp 1080p video (which is relatively low resolution).

Many if not most play other sneaky tricks too, such as focal length shortening as documented with the Nikon 70-200mm f/2.8G VR II. All of these properties are a nightmare for serious video applications.

It would be interesting to know if Canon’s new 200-400mm f/4L IS is parfocal—there is a “Power Focus Mode” but the word 'parfocal' is not used. The high price probably reflects considerable efforts in all areas, and possibly parfocal-mitigating behavior.

Zeiss parfocal zoom lenses

Lenses like the Zeiss CZ.2 70-200mm T/2.9 and Zeiss CZ.2 28-80mm T/2.9 are true parfocal zooms (“No focus shift over the zoom range”). This is a much more challenging design goal to meet, and the price at around $20K reflects this and other optical excellence.

Would I love to own them? Sure. Would I like to carry them for stills? Definitely not, but for some uses (on a tripod) the weight could be tolerable, given the assumed ultra-high image quality. And for video usage, one is likely to have a video rig with tripod much of the time.

  • Interchangeable mount
  • Full-frame coverage (36 x 24 mm)
  • No focus shift over the zoom range
  • Robust cine-style housing
  • Circular shape of iris
  • Great flare suppression
  • Calibrated focus scales
Zeiss Compact Zoom CZ.2 70-200mm T/2.9
Zeiss Compact Zoom CZ.2 70-200mm T/2.9 specifications


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