For the most part, this site concentrates on the still capabilities of mirrorless cameras. Virtually all mirrorless cameras have video capabilities, though, and some are quite good, as good as professional video systems.
If video is important to you, you need to look at several things about these cameras that I don't tend to write about much in reviews:
- Lens motors. Some lenses are better for video use than others. In the m4/3 world, they tend to call lenses designed for video use with the moniker MSC. But what's that really mean? Why would a lens be different for video versus stills? First, continuous focus performance is usually optimized in the lenses camera makers sell. That typically means a faster autofocus motor in the lens, one that can quickly change direction of focus quickly. Second, video-optimized lenses are quieter so that focus and zoom sounds don't actually get picked up by the microphones recording the audio for a video clip. The 10-100mm Nikkor for the Nikon 1 system was eerily quiet, for example, while the kit lens (10-30mm) could make enough noise to be heard by the camera's microphone while focusing, plus when you manually zoomed it you may make enough noise to be picked up, too. The current Nikon Z lenses are very quiet, but not completely silent. Ditto Canon RF and Sony FE lenses. On-camera mics tend to pick up motor noise, while off-camera mics don't. Some Nikon and Sony cameras have the ability to move the focus more silently, but this comes at the expense of focus speed. Bottom line: verify that the lenses you'll use for video don't create issues.
- Lens speed. One of the draws of using a mirrorless camera for video is that most have a fairly large sensor, and with the right (fast) lenses, you can get Hollywood-like focus effects. What's that mean? It means backgrounds (and sometimes foregrounds) thrown out of focus. The small sensors used in many video cameras, even professional ones, have historically provided more depth of field than Hollywood film cameras. But an APS-C sensor is almost the same size as the typical camera used on a feature film, so with decently fast lenses (f/1.4 to f/2.8) it can mimic the looks that the Hollywood directors of cinematography get. On a m4/3 body, with its slightly smaller sensor size, you typically need faster lenses to get the same effect (e.g., the 25mm f/0.95 Voigtlander, or any of the f/1.4 lenses). Small medium format cameras such as the Fujifilm GFX line can produce better-than-Hollywood depth of field isolation, as can very fast full frame lenses such as the Nikkor 58mm f/0.95 NOCT. Bottom line: fast lenses allow you to create more Hollywood-like looks.
- Lens Breathing. We have two types of breathing that can be problematic when using a lens for video: focus and focal length breathing. The former occurs when the framing angle changes as you roll focus; the latter occurs when you zoom and focus change simultaneously. Both create a distraction to the viewer that you probably don't want, but focus breathing, in particular, is the one most video users try to avoid. Nikon has made a big thing about this with their Z-mount lenses, virtually none of which focus breath. Sony has now been doing something similar with recent lenses, and has added a function in some cameras to help suppress it more. Note that both Nikon and Sony in some cases suppress focus breathing using real-time lens corrections as opposed to better optical design. That's proven to be effective, and I'm sure we'll see more of that in the future.
- Audio capabilities. Almost every camera has in-camera microphones, but these coupled with "Auto" recording levels will just cause you frustration. Look for cameras with an external microphone capability and the ability to control audio gain. If the camera doesn't have the latter, then you might need to run an external microphone through an external mixer prior to connecting it to the camera (e.g. Beachtek, Silicon Designs, etc.). Some videographers just do the Hollywood thing and use separate audio equipment. A really good digital audio recorder is surprisingly inexpensive, and it's relatively easy to combine audio and video output with third-party software, such as Pleural Eyes. Some mirrorless cameras also have a powered connector inside the hot shoe that allows microphones to be mounted in the hot shoe and work fully in the digital realm. Canon and Sony are both doing this with many recent models, and it's the preferred way to use an on-camera microphone. Bottom line: audio in the camera may not be optimal, so make sure you have an external way of capturing good audio.
- Manual video control. One thing that runs throughout all the best video advice is the fact that videographers need more manual control over things. If you use auto audio gain, auto white balance, and auto exposure you'll find that you'll have a difficult time keeping transitions (edits, dissolves, etc.) from being "jarring." Any change across scene cuts that's not controlled by the videographer is asking for viewer disruption. Most videographers, therefore, want to control exposure and white balance manually. Indeed, the high-end ones want to control even more than that, including gamma and other settings. Only a few of the older mirrorless cameras have full manual video control (e.g. GH2, GH3, GH4, V1, V2). Most of the newer ones do have full manual video control. Bottom line: exposure, focus, and white balance changes that happen automatically can be jarring; look for cameras that allow you to adjust the speed at which they happen, or give you full manual control.
- High bandwidth. Virtually all video is compressed (though we do now have many cameras that can record raw, either internally or externally). Just like JPEG compression throws out data, all the video compression schemes throw out data. In fact, some throw out so much data that you can see clear differences between outputs. Compression is sometimes referred to in bandwidth terms (how much actual data is in the video stream), such as 18Mbps. A little math: 1080P is basically equivalent to 2mp. 2mp times three 8-bit colors (RGB) would be 6MBs of data per frame. 30 frames per second therefore would be 180MBs of data. Thus, 18 megabits (18Mbps) is a severe compression: for every bit we have left, we originally had many, many more. The way most of these compressions work is that there's a key frame that's recorded something akin to what JPEG might give you, then only differences in subsequent frames are saved, and even those tend to be compressed. That's a gross oversimplification, but the point I'm headed towards: more bandwidth is better. If you have the choice between two cameras, one that records 18Mbps and another that records 24Mbps, and all else is equal, you're going to want the one that uses the higher bandwidth. AVCHD, which many mirrorless cameras use, originally had a maximum bandwidth of somewhere around 24Mbps, which was an attempt to make sure all Blu-Ray equipment could keep up with it. Things have changed since the original definition, and there's now an AVCHD II, plus hackers have come up with all kinds of other compressions on the GH2, some hitting bandwidths higher than 100Mbps. Modern cameras can have bitrates of as high as 600Mbps, and again, some are now allowing you to record raw video, which is the entire data stream the camera is producing. The terminology gets confusing, though, so I suggest you just look at what the maker says the output is at its highest quality and use that as a general guideline for what the quality might be between two models. One thing to be careful of is that 100Mbps for 4K at first glance looks better than 50Mbps for 1080P, because 100>50. However, 4K video has four times the pixels, so 100Mbps for 4K is actually more compression than 50Mbps for 1080P. Bottom line: higher bit rates are better, all else equal.
- Rolling shutter. Here's the dirty secret of still camera video: it doesn't pull off all the data for a video frame at the same time (there have been some exceptions—the Nikon 1 seemed to come close to what is none as does a global shutter, as do the current Sony A1, A9 Mark III, and Nikon Z9). Instead, most cameras pull off rows of data at a time, in sequence. But what happens if something that covers much of the frame moves between those row grabs? The object gets slightly offset in each subsequent row. We call the technique to grab sequential data "rolling shutter," and some cameras are far worse at this than others. One hint at how well it might do is what its maximum frame rate is. A camera that can perform 1080P/60 tends to have fewer rolling shutter impacts than one that can only do 1080P/30 (it's implied that the row grabs can be 2x faster). That's not perfectly true of every implementation, but it's a reasonable rule of thumb. That said, rolling shutter seems to go away more and more with each generation of sensor. Bottom line: look for cameras with little or no rolling shutter, particularly if you're going to record action or move the camera during a shot.
In terms of mirrorless cameras that work well for video, there used to be one elephant in the room: the Panasonic GH. The GH1 (later replaced by the GH2, GH3, GH4, GH5, and now the GH5 II, GH5s, and G6) became quite popular with videographers, partly because these models have so many professional video features in them, but also because they create very good quality video images.
The GH5 II and G6 ship with a number of small things that make it handy for video, including a cropped-video ability that pulls direct pixels off the sensor and provides some stunning "telephoto" video capabilities. Beyond that, it had excellent compression from the get go. There's plenty of manual control on a GH5 II and G6, as well (at least if you can figure out the absolutely opaque manual). More so than any other mirrorless still camera, the GH5 II and G6 excel at video work. At least up to 4K.
Since I originally wrote the above, the full frame mirrorless makers have upped the game. If you're looking for "best possible" video quality, the Canon R5, Nikon Z6 II or Z9, Panasonic S1H or S5, and the Sony A1 and Sony A7S Mark III all will stand up and fight for that title of "best video" (in slightly different ways).
That's not to say that the rest of the mirrorless cameras can't be used for great video. I've seen plenty of video examples off of virtually all the current mirrorless cameras that stand up against work done with pro video equipment. That's become more true with each mirrorless camera generation. My current Z9 produces 8K raw video that's essentially state-of-the-art (as of the date of this article update).
The fewer of the problems I mention above that are in your mirrorless camera, the easier it will be to create great videos with them. That said, I've even used an older Sony NEX-5 for theatrical work and the original Nikon V1 for wildlife work with success. Another big plus: these were small cameras and can often be put just about anywhere.
You may have noted that I wrote "mirrorless still camera" several paragraphs ago. Does that imply that there might be mirrorless video cameras, too?
Absolutely.
Technically, all video cameras with interchangeable lens mounts are "mirrorless," as no video mainstream video camera uses a mirror the way still cameras do. Canon, Panasonic, Sigma, and Sony have come up with dedicated video cameras that use their mirrorless still camera mounts. Blackmagic Design and a few others have dedicated video cameras that use existing still camera lens mounts.
In the case of Sony, they have a lineup from the discontinued prosumer video camera (VG-30) to the current professional (FX-3/FX-6/FX-9) that can all use the Sony E-mount lenses. I used to use a Sony FS-100, and I'm comfortable in writing that even it was good enough that I'll never shoot 35mm movies again. It was a strange beast in terms of design—as are most professional filmmaking and dedicated video cameras—with more buttons and controls on it than you can count on a big family's hands. But in serious video work, there's usually more than one person at the camera (director of photography, camera operator, focus puller, maybe another grip or two). Things work differently in the pro world (and more slowly) than just trying to take some video of junior's birthday party. Everything is controlled, and you need to be able to see what those settings are quickly and visually.
So here's my advice:
- If you do pro video work. Jump right to a real video camera. It's out of the realm of this Web site to say whether that's a Blackmagic Design, RED, a Canon Cinema, a Sony XDCAM or XF model, a Panasonic Varicam, or something else, but you need and will appreciate something that was designed for video and is high performance. That's not to say that you wouldn't sometimes use a mirrorless still camera for a second camera, a disposable (in jeopardy) camera, or for shots that are in tight spaces or where you need to move the camera more freely. Your choice of a small still camera for video would likely follow what you buy for your primary camera (if for no other reason than to share lenses). For instance, a Sony A7 still photographer should be looking at the Sony FX video cameras. Indeed, the FX-3 is basically a Sony A7S III but in video style body and controls.
- If you're a budding videographer. This is where something like the GH6 (or even a used GH5) looks very appealing: it has real video credentials, it's not overly expensive (cheaper than prosumer camcorders), and it'll produce output that's more than usable. That said, a lot of the recent full frame cameras create quite good video, too. In particular the Nikon Z6 II and Z9, the Panasonic S1H and S5, plus the Sony A1, A7S Mark III, and A7 Mark IV/A7C.
- If you want to dabble at a little video. If you're in this category, then all of the current mirrorless cameras probably have enough video capability in them now to satisfy you. You probably don't really need 4K; solid 1080P—now referred to as Full HD—works just fine for most uses, and virtually every camera can produce really good 1080P. Look only at the features I list at the top to narrow down between two cameras if you need to, but don't get overly anal about that. In other words, if you're in this category, the video capabilities aren't likely to be the deciding factor of which camera you pick.
Finally, you should probably learn the difference between sampled, overscan, and full scan in terms of pixel use, particularly when it comes to 4K video:
- In a sampled camera, pixel rows (and sometimes columns) are usually skipped and that can produce artifacts.
- In an over-scanned camera, the video is sampled with 5K or 6K of data typically, and that's downsized to 4K. Overscan is good, but it can anti-alias edges (soften them).
- Full scan means that there's a one-to-one correspondence between the capture pixels and the output pixels. Full scan is typically what you want for best results.
