Autofocus or 1st AC? Canon RF 15-35mm F2.8 on the Canon C70

Has autofocus gotten good enough to replace the focus puller?

Jul 8, 2023

Last week, I had to choose between hiring a 1st AC or going with autofocus on the Canon C70 for an ad. The ad was a "one take" style, the camera was on a gimbal following the talent, and the talent was navigating a series of actions while delivering their lines. We needed to roll in four cars, build lighting, and block out the shot with six total people on camera before 10 am. And we had to shoot the ad four times with four different leads.

One of the five photos I took that day. The rest were of birds. It pays to hire a BTS photographer!

If you're playing it safe, you'd bring on a camera assistant, who mounts their monitor and follow focus on a stand and magically maintains focus for the director of photography throughout the day. In this scenario, they'd learn the movement of the talent in the blocking period and nail it every time during the takes. They make the shoot more efficient by reducing the number of retakes from focusing mistakes.

I haven't hired a dedicated 1st AC for my projects and my aim on Feed the Sensor is not to act bigger or more experienced than I am at producing or director of photography work. I got my experience working on scrappy small team jobs in the New England area before moving to Seattle. I have been on 40+ person jobs and have worked as a camera assistant, but where I've put in most of my time is small solo to six-person projects.

I bring this up because, without this experience, I don't think I would have even thought to use autofocus over a 1st AC. Here in Seattle, what has been notable to me is how unnecessarily large the crews can be. When you've got two interviews in a full day, do you really need a 1st and 2nd AC?

Rather than bringing on an assistant, you could utilize autofocus and cross your fingers that it'll work.

Here's where it gets sticky for me. I own a Canon C70. This camera gets a lot of flack for having poor autofocus. From what I read and hear on YouTube, Sony is the king at autofocus and Canon should not be trusted because it hunts or does one of those full zoom racks when it loses its tracking. Remember back when Canon with their dual pixel autofocus in the C100 days was the best out there? Sony took over that lead, and people are not wrong about that. The autofocus on the FX lineup is impressive.

But I have a theory that at least some of the distrust in the autofocus on the Canon C70 comes from people using legacy lenses through the 0.71x adapter. Autofocus is certainly not as good through the adapter. This is anecdotal. Surely I can't be the only one that bought the C70 thinking I could finally get some near full-frame imagery out of my old EF lenses, right?

Anyway, when you pair the C70 with modern RF lenses, the autofocus is right up close with Sony's FX6 and a native Sony lens. The modern RF lens I got is the Canon RF 15-35mm F2.8. It is my new do-it-all lens for the camera, a lens akin to the Sigma 18-35mm F1.8 on a Panasonic GH5 with Metabones speed booster.

The RF 15-35 F2.8 is a fantastic lens. It is a lightweight compact normal zoom with the best image quality that I've ever gotten out of a photo zoom lens. There's no question. It's tack sharp throughout the range, the color is neutral, the focus falloff is natural, and the range is nearly perfect (around 21mm to 50mm equivalent). What I see with my eyes is what this lens sees, and this makes for a very useful lens for your standard corporate work. Does it have character? Absolutely not. It's boring as it comes. However, I couldn't ask for anything more if I'm looking for a lens that captures what I need without a concerned client pointing at the frame and pondering, "The edges… They're a little fuzzy, y'know?"

Autofocus is no joke on this lens, either. After a few jobs in which I found the autofocus accurate and reliable for B roll, it became clear that I could get away with using it for interviews and even on fast-paced, moving shots, particularly on jobs that didn't have the budget for an AC. This thinking led me to choosing autofocus with this lens over a camera assistant on this ad.

Let's go through how this lens performed in chronological order for the day.

At the start of the day, I had my full C70 kit, the RF 15-35mm lens, and a Ronin RS3 Pro package. By about 9 am, I had everything built and ready to go and was helping adjust lighting. By 10 am, the talent had arrived and off we were with blocking. In those first couple of hours, I noticed several things about this lens.

First off, once mounted to the RS3 Pro, I could adjust the zoom without having to rebalance the gimbal. This ability saved time later in the day when we had to capture pickup shots at different focal lengths. I just reached over and adjusted it. Though partly attributable to the gimbal, this lens is well-balanced through its focal range.

Secondly, it's just the right size and weight. At 837 grams and about 5" in length, the lens is easy to balance on the gimbal with the C70. The actors for the day were all tall people, so I was unable to use the provided EasyRig (unless I wanted up-nose shots). For this reason, I went handheld using a Tilta Ring for the Ronin. The low weight of the lens saved my back. Ten hours of walking with a camera out in front of me is a guaranteed visit to the PT. I didn't have that problem with this lens.

About ten minutes in to blocking with the talent, I came across the first autofocus issue. The shot starts out with focus nearly at infinity. The talent walks into the frame and toward the camera. I match their pace. The time it took for focus to adjust from near infinity to about fifteen feet was too slow. The talent would be talking but their face would be a blur. Uh oh!

Inside the C70 menus, you can adjust several autofocus settings. I set the autofocus speed to the maximum and we ran through the shot again. The problem was resolved; the camera immediately switched from near infinity to a tack-sharp lock on the talent.

By about 4 pm, we had captured the content for all of the talent. During this time, I had grown to appreciate the RavenEye system on the DJI Ronin, which transmitted a video feed to an iPad for the entire day without fail.

I also began to worry just a hair about the autofocus.

The RavenEye transmitter sends a good quality signal, one that is better than the Hollyland and Accsoon transmitters that I've used, yet the signal is not strong enough to check for focus in a pixel-accurate way. Was the camera breathing slightly during the takes? Was it just off the eyes, perhaps on the nose? How could I know without a large monitor to look at?

Weird things can happen on set, such as a nearby lightning storm bricking a light or a microphone picking up the disc jockeys on the local radio station chumming it up about a fundraiser, and not knowing with 100% confidence that slightly miscalculated focus was one of those weird things was distracting enough to discourage me from running solely with autofocus again.

Days later, I closely examined the footage. Weird things had occurred: a "micro shift" in the focus plane from the nose to the eyes, or from the eyes to the ears, and back. It would be a brief pop out and in, something you'd miss if you blinked or were not inches from the monitor like I was. Thankfully, with the number of takes that we captured with each talent, it was possible to cover up the areas where this happened.

So all is good, right?

My takeaway is that I would not use autofocus on a job like this again. I could not confirm autofocus with a level of confidence that a person pulling focus could do with a simple thumbs up. It was an unknown, and not knowing proved distracting, taking my energy away from other activities on the job. At the very least, if I were to do this again, I'd have someone watching a 17" monitor during the takes who could give that thumbs up of confidence.

The Canon C70 and Canon RF 15-35mm F2.8 performed well together. I have no complaints about this camera and lens combo. If you're looking for the ideal lens for your Canon C70, give the 15-35mm a try as a rental. You'll find that though it's expensive at $2,200 (or as low as $1,500 used), it gets its value by taking the place of a 21mm, 28mm, 35mm, and 50mm F2.8 lens set and not requiring lens swapping. Performance is excellent. That it is part of the new RF mount lineup means it'll be of use for many camera bodies to come.

If you could fault this lens, it would be that it's boring. What you see is what you get, nothing more. So, if you’re subject is boring, then, well, better get creative with the camera!

I already wrote that this neutrality of a lens is something I appreciate for corporate work, but what about you? Would you rather capture "the look" in the camera with specialty lenses or capture a neutral shot with this lens and make "the look" in the edit? How come?

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