Adapting Servo Zoom Lenses for Smooth-Zooming DSLR Production, Part 1

The Servo Zoom in Action

I've shot some video to accompany this article to demonstrate how the servo zoom looks compared to trying to zoom the Panasonic 14-140 lens. You can see how adding a motor to the lens makes a considerable difference in the ability to zoom smoothly throughout the range of the lens.

It also enables a "ramping" zoom where it feathers in, zooms faster in the middle, and then feathers out, much like a bezier curve when applying motion in post, as you can see in the clip below. Again, newer, better zoom lenses will feather in and out even nicer than this one.

Advantages of Using a Servo Zoom

Using a servo zoom lens provides multiple "prime" lenses much like a DSLR's zoom lens. The ENG lenses often offer much lower f-stops like 1.6 or so. But unless you're buying a better, newer HD servo zoom lens, I recommend staying above f2.8-4 to minimize lens softness and CA. Still, you can easily set up and zoom to exactly the framing you desire, without dealing with multiple prime lenses, or having to jockey forward or backward several feet to get the right framing.

I chose this Tamron lens as a proof of a concept that I had even before I purchased my DSLR. Since purchasing the Tamron, I have added a newer Fujinon lens.

In part two of this series, I will discuss providing power to your servo zoom lens and setting up an on-shoulder system. I am also working on starting and stopping the camera recording from the REC button on the lens, greatly simplifying event coverage and making DSLRs much easier to transition to from more typical camcorders.