Here's what you need to know about setting back focus with a cinematic zoom lens.
I remember when I was first starting in video. Everything was so damn simple. You have your digital video camera (in my case we were using a friend's Canon 7D). You set everything to auto, you frame up your shot, you set your focus, you point, click, and shoot. Boom. Filmmaking, baby!
However, as you’ll quickly learn working in the film industry, shooting high-quality video is much more than clicking and recording. It takes a wide array of skills, techniques, and technical tips and tricks to get to that professional standard. One of those techniques that many starting out may not understand, or even know about, is setting back focus on a lens.
Luckily, there are great resources online, like the video below, to help you learn all the skills you’ll ever need. Check it out.
How to Set Back Focus with your Cinematic Zoom Lens
As Joey Helms explains, we get a great walkthrough not only into how and why you’ll want to use back focus but also how you can add back focusing to your cinematic arsenal.
Back focus, or as your textbooks in film school might explain, is also called focal flange length and is basically the distance between a camera’s sensor and the rearmost element of the lens. This process of flange focal adjustment, AKA back focusing, with a cine zoom lens like the ones used in the video will help videographers or filmmakers keep your actors or subjects in focus as you zoom in or out.
Traditionally adjusting back focus has been a painstaking process where you have to actually take apart lenses to add or remove thin metal rings. However, in the video Helms recommends using cine lenses like the ones made by FUJINON which have a built-in adjustment ring.
10 Steps for Setting Back Focus
- Put camera on the tripod
- Point camera at focus chart or solid object
- Place camera 6 feet away for a wide-angle lens
- Place camera 15-20 feet away for a telephoto lens
- Open aperture all the way (use ND if overexposed)
- Turn up the contrast, turn down the brightness of the viewfinder
- Zoom in, set front focus ring until sharp
- Zoom out, loosen back focus ring until sharp
- Repeat the last two steps several times if necessary
- When set, tighten the screw on the back focus ring (not too hard)
These are the steps for setting back focus by using cine lenses like the FUJINON MK Series. It’s a pretty straightforward process but one you should take seriously and follow each step correctly. If you’re looking for professional focus for your shots zoomed in and zoomed out, you’ll want to make sure you’ve truly perfected both your focus points.
If you’re looking to set back focus with a different lens set, or interested to see how you can manage it with one of your favorite video cameras, I’d recommend searching out your specific camera/lens on YouTube to find a tutorial. Here are some examples to check out as well.
- Setting Back Focus w/ RED DSMC2 Cameras
- Setting Back Focus w/ Sony A7iii
- Setting Back Focus w/ Broadcast Lens
- Setting Back Focus w/ Sony PMW-200
- Setting Back Focus w/ DZOFILM Linglung Lenses
Have any suggestions for setting back focus? Let the community know in the comments below.