Quick take: This is part two of my ongoing Sigma BF review, and this time it's all about video. Video autofocus struggles out of the box, but half-pressing the shutter while recording makes tracking lock on and stick. Photo autofocus is better than Fujifilm's and a huge leap from the fp L. My theory is that this autofocus software is a test run for something bigger: a new fp or a full flagship hybrid from Sigma.
How I Tested It
Everything in this video was recorded on the Sigma BF with the Sigma 20mm F2, going out to an Atomos Ninja V. One annoyance right away: the Ninja can't mirror the image, so framing yourself takes a little more effort than it should.
The talking-head shots were lit with a single Amaran light set to 5,500K, at ISO 400, and nothing you see has been graded. That way you're seeing exactly what the camera gives you.
Video Autofocus: Bad Until You Know the Trick
My first test was simple. I had Devon walk toward the camera, and the BF did not do well. Focus wandered and it didn't hold onto her the way a modern camera should.
Then I found the trick. If you half-press the shutter button while you're recording, the camera grabs your subject and tracking actually sticks. Once I started doing that, the results changed completely.
On talking heads it tracked me better than my Fujifilm X-M5 does. It wasn't perfect, though. On close product shots I saw some pulsing as the lens hunted back and forth, so it's not something I'd trust for detailed B-roll yet.
Photo Autofocus Is the Real Surprise
For stills, the autofocus is genuinely good. It's better than what I get from Fujifilm, and compared to the fp L, it's a huge leap. That's the part that got me thinking about where Sigma is heading.
My Theory: This Is a Test Run for a Bigger Camera
Sigma makes some of the best L-mount lenses out there. The problem is that other camera makers don't make life easy for third-party lenses. Sony, for example, limits third-party lenses to 15fps.
So if Sigma wants its lenses to really shine, the best move is to build a body that gets the most out of them. I think the BF's autofocus software is Sigma testing the waters. My guess is it ends up in a new Sigma fp with strong autofocus, or even a flagship hybrid camera.
Image Quality and Color
The BF has some fun built-in looks. Teal & Orange is there if you want something stylized, but Rich is my favorite. Straight out of camera and ungraded, the footage looks great for a talking-head setup.
What's Missing
There's no autofocus speed control, so you can't slow down or smooth out focus transitions.
Storage is internal only, with no card slot, so it isn't built for long client shoots.
The video autofocus needs that half-press trick to really work, which isn't obvious.
Final Thoughts
The Sigma BF isn't a video powerhouse yet, but it's a lot better than it first seems once you learn how to work with it. The photo autofocus is excellent, the color is lovely, and I think it's a preview of what Sigma has coming next. If they put this autofocus in a more video-focused body, it could be a big deal for L-mount shooters.
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