What Is a Parfocal Lens? What It Is & Why It Matters

Reading Time: 4 minutes

Published: September 22, 2025

Why Parfocal Lenses Matter (With Examples)

Parfocal lenses give you full control over focus while zooming. You can reframe from a wide shot to a close-up without losing sharpness. That saves time and (to an extent) eliminates the need for a focus puller during zooms.

This is helpful when filming:

• Live news or events – where you can’t afford to lose focus mid-zoom
• Documentaries – where zooming is part of following action naturally
• Run-and-gun shoots – where you may not have time or crew to refocus manually

One of the most famous uses of parfocal zooms is the crash zoom, a fast zoom-in or zoom-out that keeps the subject sharp. Directors like Quentin Tarantino often use this technique to highlight a reaction or create tension.

Parfocal lenses also make it easier to pull off a dolly zoom (also called the Vertigo effect). This move combines zooming with dollying to stretch or compress the background while the subject stays the same size. Without a parfocal lens, the shot becomes much harder to keep in focus.

Parfocal vs. Varifocal: What’s the Difference?

Varifocal lenses do not maintain focus while zooming. If you change focal length, you’ll need to refocus afterward. Most photo zooms are varifocal because they’re smaller, lighter, and cheaper to make.

Parfocal lenses are built to hold focus as you zoom. This requires precise internal mechanics, which makes them more expensive and usually heavier. But they’re worth it for consistency in video production.

How to Test if a Lens Is Parfocal

You can test a lens yourself. Here’s how:

1. Zoom all the way in (or out) on a subject.
2. Focus carefully.
3. Zoom in/out slowly.

If the subject stays sharp, the lens is parfocal. If it gets soft or blurry, it’s varifocal.

Some lenses claim to be parfocal but still shift slightly. That’s why professionals test lenses before important shoots. The excellent Sigma 18-35mm and Sigma 50-100mm, for example, vary in this regard. Some copies are varifocal, while others are not.

The First Parfocal Lens

French optical engineer Pierre Angénieux developed one of the first modern parfocal zooms in 1956: the 12–120mm f/2.2. lens for 16mm cameras. It became a standard in newsreels, and later in documentaries and TV. Today, Angénieux remains a top name in cinema optics.

Vintage Parfocal Zooms Filmmakers Still Love

While true parfocal vintage lenses are rare, there *are* some older zooms that many creators report to behave well enough when zooming, especially after testing. Below are a few examples with current used-market prices (USD, GBP, EUR) plus what to watch out for. Prices vary by condition and seller.

Lens	Focal Length Range	Max Aperture	Sensor / Mount Compatibility	Approx Price (USD / GBP / EUR)	What to Test / Caveats
Canon FD 35-70 mm f/4	35-70 mm	f/4 constant	35 mm stills; good with adapters to mirrorless / S35	≈ **USD 300** / **GBP 230** / **EUR 270** (used, typical)	Test for focus shift when zooming; may be only nearly parfocal; relatively slow; stops down helps sharpness.
B4-mount ENG zooms (old broadcast models)	Varies (e.g. ~9-90 mm, 14-140 mm etc.)	T-stop ~2.8-4 at wide end	Made for 2/3-inch B4 sensors; need optical adapter to use on larger sensors	≈ **USD 400-800** / **GBP 320-650** / **EUR 360-750** depending on model & condition	Check adapter quality; expect vignetting or edge softening; test parfocal drift; heavy lens weight.
“TV Zoom” lenses (C-mount / 1-inch / older video zooms)	Ranges like 12.5-75 mm, 16-100 mm etc.	Often f/1.4-f/2 or f/1.8 at wide end	Good for smaller sensors (C-mount, 1-inch, 2/3-inch); may need adapter for larger	≈ **USD 80-250** / **GBP 65-210** / **EUR 75-230**	Likely varifocal but some perform well; image quality falls off at long end; check for front-element changes; possibly strong distortion / chromatic aberration.

Other well-known (and more recent) parfocal zooms include the Fujinon Cabrio and Canon CN-E lines, both designed for professional film and broadcast work.

Using These Lenses: What You Need to Be Aware Of

Even with “good enough” vintage zooms, you’ll want to check several things before you commit.

First, adapter mounts: many of these lenses use mounts alien to your camera, flange distance, focus to infinity, and whether the adapter optics maintain edge sharpness are crucial. Second, sensor coverage/image circle: a lens made for smaller formats (C-mount, B4, 16 mm etc.) might vignette or have darkened corners on Super35 or full frame sensors.

Next, true parfocal behavior is rarely perfect: test zooming through the range after focusing, see if drift or focus shift occurs. Aperture and light loss matter too; many older lenses get soft wide open or at long zooms, so stopping down (to f/4-f/5.6, etc.) helps.

Also, be mindful of lens breathing, distortion, and flare, which tend to be more pronounced in vintage zooms (sometimes this is desired, sometimes not).

Mechanical condition is another big one: zoom creep, loose focus rings, haze, fungus. These affect not only image quality but parfocal stability. And because many vintage zooms are bulky or front-heavy, support (tripod, rails, rigs) becomes more important. Finally, physical handling: moving front elements, weird filter sizes or threading, zoom/focus ring configuration, all add friction or unpredictability when shooting.

Summing Up

A parfocal lens keeps your subject in focus as you zoom. It helps you save time, avoid blur, and execute complex zoom-based shots without adjusting focus. Whether you’re shooting a movie, covering live news, or working solo, knowing how and when to use a parfocal lens keeps your footage sharp, literally!