You’ve heard the terms “varifocal” and “parfocal” to describe lenses, but do you know what these terms mean? Or why they matter? If you don’t, this informative conversation between Vistek video producer Dale Sood and product manager Brian Young is the perfect place to start.
Varifocal and Parfocal describe two different types of zoom lenses based on whether or not the focus is maintained when you change the focal length.
With varifocal lenses, as soon as you zoom the lens you are varying the focus (hence the name). Any amount of recomposition is going to change the focus, which is why these lenses were designed for still photography—you tend to refocus every time you change the composition anyway, so it’s no big deal.
In television, video and cinema, however, changing focus is a big part of the creative process. Pulling focus shifts the emphasis onto a different subject, and a parfocal lens allows you to change the focal length without altering your focus. So you can zoom into the subject, focus, and then zoom all the way back out while maintaining the same point of focus.
Additionally, Parfocal lenses also minimize a troublesome phenomenon known as “lens breathing.” In a varifocal lens, as you adjust the focus, the edges of the frame tend to shift. This can be jarring to the viewer when you’re pulling focus in a video, and so parfocal lenses are designed to nearly eliminate focus breathing.
You can see the difference clearly in the GIF below:
As DSLRs have gained more and more impressive video capabilities, the line between stills camera and video camera has blurred almost beyond recognition; at the same time, the line between video and stills glass is still very distinct. If you want to shoot video, you need to learn the differences: not just parfocal vs varifocal, but f-stops vs t-stops, and more.
And if you enjoyed this video and want more tips, tutorials, and educational videos on photography and filmmaking, check out all of Vistek training videos on their YouTube Channel.
(via ISO 1200)