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Sony a6400 First Impressions: Improved Autofocus and Video Capabilities

Last week, Sony announced the 24.2-megapixel a6400 APS-C mirrorless camera and I first got my hands on it. Here's a rundown of all my thoughts on it so far and how it performed with the 18-135mm f/3.5-5.6 OSS kit lens.

With a sizable range of lenses one could use with Sony's new crop-sensor camera, I decided to stick with the kit lens for my testing to see how many, if not the majority, of people would probably be experiencing this release. The Sony a6400 is priced at $898 for the body only, and $1,298 when purchased as a kit with the 18-135mm f/3.5-5.6 OSS lens. Buying the lens separate is $598, so that's nearly $200 of savings if one decides to get the kit off the bat. I'll say up front that this combo was versatile (full-frame equivalent of 27-202.5mm) and surprisingly solid, and Sony points out that the a6400's "world's fastest" autofocus speed of 0.02 seconds was achieved using this 18-135mm lens.

Sony a6400 Versus Sony a6300

The Sony a6400 is a follow-up to 2016's a6300, and is actually launching at $100 cheaper. Looking at the specs, however, there's nothing that looks cheaper about it. The a6400 features improvements over the a6300 in Real-time Eye AF, Real-time Tracking, 425 phase-detection and 425 contrast-detection autofocus points, continuous shooting for up to 116 raw frames, better low-light sensitivity of 102,400 ISO, touch-enabled and 180-degree tiltable LCD screen, and added HLG profile, S&Q mode, and Proxy recording for video.

The Sony a6400 uses the same 24.2-megapixel APS-C Exmor CMOS image sensor as the previous a6300, and their image quality is similar. The body design, batteries and battery life, card slot, and more that aren't mentioned in the paragraph above are likely the same or nearly the same as the a6300. The most notable improvements of the a6400 over the a6300 are found in the autofocus system, video recording improvements, and the 180-degree flip up touchscreen.

69mm, 1/100 s at f/5.6, ISO 3200
69mm, 1/100 s at f/5.6, ISO 1600


As I mentioned, the Sony a6400 has been lab tested to an impressive autofocus speed of 0.02 seconds with the 18-135mm mounted. It has 425 autofocus points for both phase detection and contrast detection which covers 84 percent of the frame. This is the first Sony camera to be released that has Real-time Eye AF, which opens up the excellent eye detection continuous autofocusing to be used anywhere without requiring a separate button to activate. Later this year, Eye AF for Animals will also be added to this camera.

The a6400 fires up to 11 frames per second with autofocus and auto exposure tracking, and up to 8 frames per second if in Silent Shooting mode.

A couple of the other neat features that are new to Sony are the abilities to manually select which eye should be in focus (left, right, or auto) and also being able to hide focus areas in the menu that you never use.

135mm, 1/1250 s at f/5.6, ISO 200

Real-time Tracking

One of the bigger autofocus developments with this camera is with the new Real-time Tracking for finding moving subjects and locking on to them. Real-time Tracking replaces what was previously labeled Lock-on AF in the camera's focus area menu. While Real-time Tracking is found in the focus area menu, it's not a specific area in itself. Within the Real-time Tracking setting, you can then choose which actual focus area to use it with (Zone, Wide, Flexible Spot, etc.) by tapping left or right.

There are three layers to Real-time Tracking and knowing them can help a little to make sense of what the camera is trying to do when its activated by tapping your subject on the screen. On the outer-most layer, the camera is going to use color, patterns, and distance to detect what should be in focus. Next, if it finds a face in the scene, it will begin to track that while simultaneously using the first layer to better hold on and also as a fallback should the face become obscured. The innermost layer of Real-time Tracking is attempting to pick up the eye on the face to really dial in the perfect focus. Now, for example, if something moves in front of the eye, the camera will still hold focus on the face, and when the face is blocked or looks away, the camera holds onto the color, pattern, and the distance it learned to stay as close to in-focus as it can.

Eye AF indicator mockup. 108mm, 1/60 s at f/5.6, ISO 1600
Real-time Tracking indicator mockup. 25mm, 1/250 s at f/4.0, ISO 1250

On the a6400 paired with the 18-135mm, Real-time Tracking is mostly just OK. I found it to be easily fooled with more than one moving subject, or not sticky enough for a fast moving subject, or puzzled as to what the subject I selected was if the lighting wasn't super great. I had all three of these taking photos of a rainy outdoor basketball game and the camera couldn't keep up with tracking the players I wanted. Indoors under studio lights with two sword fighters also had problems. When things were simplified and I was photographing a single person just walking or posing, Tracking showed it does know what it's doing, but in those scenarios having the mode obviously isn't very important. I should mention that I only had very limited opportunities to use the feature, so I'm sure there's some middle ground out there where having Real-time Tracking in the a6400 would be helpful.

Sony said the tracking and subject recognition performance is a product of the camera and lens combination (Real-time Tracking will also be rolling out to their more superior a7 III, a7R III, and a9 cameras), so the a6400 is likely to be bottom of the barrel as far as execution, plus remember I'm using a kit lens rather than one of their better spec'd glass.

135mm, 1/800 s at f/9.0, ISO 200
101mm, 1/250 s at f/5.6, ISO 1600
103mm, 1/400 s at f/5.6, ISO 5000

Manual Focusing

I only used manual focus in one situation with the Sony a6400, but I think it might be important to make note of since I know some people like adapting older lenses to E-mount cameras and sometimes manual focus is the only option. In my situation I was trying to photograph a bird in an open field and autofocus wouldn't be able to pick out a brown bird moving among the equally tall brown foliage. My best shot is below, but unfortunately it's still out of focus. I think the pixels in the viewfinder were too big and the focus assist zoom too low quality to be able to accurately determine if I had focus or not. At the time of shooting I thought I had probably gotten close enough to where the distance and depth of field would take care of the imprecision, but it looks like I was wrong.

135mm, 1/500 s at f/5.6, ISO 250


Sony claims that improvements to video in the a6400 include smoother and more accurate autofocus. While shooting 4K video the screen does not dim as it did with previous models. There's touch to focus in video mode, and now Real-time Tracking enabled by tapping the subject as well.

Sony said that Real-time Tracking for video, like any other camera mode or setting, shouldn't be set there and forgotten about. Where Sony thinks Real-time Tracking is most valuable for video is when the camera operator can't easily access the controls while in use, such as while filming yourself in front of the camera or using a gimbal.

135mm, 1/1000 s at f/5.6, ISO 6400

A few downsides to shooting video with the a6400 include a really annoying record button placement on the edge of the right backside grip, a slight crop while recording 4K at 30 fps and 1080p at 120 fps, and having no headphone output to monitor sound.

The video below shows miscellaneous sample footage shot with the Sony a6400 and 18-135mm lens. All clips shot in 4K 100 Mbps, 24 fps. Autofocus enabled on the camera (generally used Wide AF or Tracking AF) and Optical SteadyShot enabled on the lens.

As you see, having no in-body image stabilization and only the weak OSS in the lens putting in work, the footage is quite jittery even when I'm just standing in one spot. The clip where I'm walking is certainly unusable, and if I were to be filming myself walking for a vlog it would not look good at all. There's a clip in there that also exemplifies the heavy rolling shutter effect in the a6400.

One new feature in the a6400 is a time-lapse mode. The options available to configure are the start delay time, shooting interval time, number of shots, AE tracking sensitivity, and a silent shooting toggle. At the bottom of the menu screen it displays the total shooting time required based on selections. Once the time-lapse recording begins, it can be stopped at any point so it might make sense to set the number of photos taken way higher than you need and just manually stop once you think you got what you need. The images shot for the time-lapse are outputted as regular raw photos on your memory card, with no video file created in-camera. Videos need to be created on the computer either with Sony's free Imaging Edge software or with the third-party editor of your choice. On the camera, however, you can view a sample video and you can even adjust the playback speed of the time-lapse shown.

The a6400 can be powered with an external power bank, which is helpful for extended time-lapses or video shots. There is no hard 30 minute recording time limit, rather it depends on the size of the memory card and factors such as camera overheating (there are two sensitivity options for when the camera will shutdown from overheating, one regular mode and one that will allow more heat buildup).

91mm, 1/100 s at f/5.6, ISO 1250
135mm, 1/60 s at f/5.6, ISO 500

Other Thoughts

  • From what I've read, a lot of people aren't too happy with the choice to use a 180-degree flip up screen. The complaint is that when you have an accessory mounted to the hot shoe, it blocks the screen. In the context of the a6400 being marketed as a vlogging camera, I can understand the head scratching since most vloggers are going to want to mount a shotgun microphone or a lav mic receiver. But this supposed vlogging camera also doesn't have in-body image stabilization or a headphone out plug, so I think marketing was trying to fit a square peg in a round hole for a few things here. I'm primarily a stills shooter, and the flip up is faster and a lot less awkward using for low-angle photography versus the horizontal flip-out style. If you intend to use the self-portrait mode screen with an accessory, you'll want to get a cage or straight flash bracket (however, realize that your microphone will be off center then).
  • I thought the LCD screen made it hard to see anything in sunlight, however in retrospect I forgot I could have probably bumped up the brightness in the settings.
  • Two batteries lasted me two days of shooting. I was doing a mix of both photos and 4K video. I know at least one heavy video shooter was eating batteries though while testing. The a6400 uses the older style battery that the previous a6000-series cameras used, not the new ones in the third-generation a7 bodies.
96mm, 1/200 s at f/5.6, ISO 100
  • Sony has had touch-enabled LCD screens for a decent amount of time now and there still is very limited functionality with it. Tap to focus and swiping through the Playback screen is about all we can do.
  • This summer, firmware version 2.00 will be released which will contain the ability to use Eye AF on animals. Sony said the user will have to toggle between either human or animal in the menu. I don't particularly like the idea of even more menu items to remember to change and wish it could be set to automatically figure it out or have a way to prioritize looking for one before trying to find the other. And if you want maximum speed, then sure, set it to one or the other.
  • Speaking of the overwhelming menu system, Sony has so many interconnected settings that sometimes when you try to change something in the menu, you get a prompt that says it can't be done because another setting elsewhere needs to be changed first. They give no clue as to where to find the other setting that needs changing in the prompt, which means you have to go and hunt it down among the hundreds of options. I wish the prompt would either show the page and item number where to find it, or let me press a button to bring me right to it.
  • If this release isn't quite what you expected and you wanted more, I think the fact that the new firmware features won't be coming to the higher-end a6500 and the distinct lack of key hardware features in the a6400 is confirmation that a better APS-C camera will be coming soon enough.

Overall, the Sony a6400 is an incremental upgrade over the a6300 with just enough incentive to paying a bit extra to buy the new model over saving a few bucks for the old. The Sony a6400 is available for preordering as a body only for $898, as a kit with the 16-50mm f/3.5-5.6 OSS lens for $998, or as a kit with the 18-135mm f/3.5-5.6 OSS lens for $1,298 which is what I used. Cameras will begin shipping on February 28, 2019.

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Lee Morris's picture

I'm excited about this camera. So affordable with incredible video features.

David Penner's picture

Me too. I am considering it just for video. I've got the A7ii which I'm happy with for photos. This would be something nice and small for throwing in the bag when I want to do some video.

Deleted Account's picture

Love sandpipers! :-)

Eric Salas's picture

For 900 bucks, you really don’t have much to complain about.
You’ve still got money for gimbals, mics, lavs, lights, etc so if this is directed (as it is) towards Vloggers/budget market, they did a good job merging the a5100 and a6300 bodies while updating AF.

g coll's picture

Seriously considering this. Could be the ultimate hybrid im looking for when I need to pack ultra light.

Mark Holtze's picture

I'm excited as well! I think the price is amazing ,but I think this camera should be aimed at all photographers and not even bother specifying "vloggers". That flip up screen is handy for framing even if you aren't shooting yourself.

Small size, no limit video recording, does 4k, shoots log, 24mp ,great AF.

I'm curious because I'd like to test out an APS-C sensor camera for adapted vintage lenses. I think combined with those old SLR lenses this camera and the attractive price point, small size makes it really attractive to even seasoned hobbiest photographers.