Sony a6400 (ILCE-6400) with the Sony Zeiss 16-70mm F4 zoom. Photo: David (Brokentaco) via Flickr, CC BY 2.0 (resized)
HIGHLIGHTS
The a6400 is how a lot of people get into Sony's APS-C system. Announced in January 2019 as the successor to the a6300, it pairs a 24.2-megapixel APS-C Exmor CMOS sensor with the BIONZ X processor and 425 phase-detection points covering about 84% of the frame. Sony claimed the world's fastest autofocus among APS-C cameras at the time, 0.02 seconds, and the a6400 introduced both Real-time Eye AF and Sony's Real-time Tracking mode.
That autofocus is still the reason to buy one. Eye AF works in every AF mode with a half-press, tracking follows subjects across the frame, and bursts run at up to 11 fps with AF/AE tracking (8 fps with the silent shutter). Video is 4K from full pixel readout with no binning, plus S-Log2, S-Log3 and HLG, and 1080p at up to 120 fps. The screen flips up 180° for selfies and vlogging, there's a 2.36-million-dot OLED viewfinder, and the body weighs 403 g with battery and card. DPReview called its autofocus one of the best implementations on the market, "not just in its price range".
The compromises show elsewhere. There's no in-body stabilization, so you rely on lenses with OSS or VC such as the Tamron 17-70mm F2.8. DPReview measured a 1.2x crop at 4K/30p and pronounced rolling shutter, and there's one UHS-I SD slot, a 921k-dot screen and no headphone jack. If you want IBIS and Sony's newer AI subject recognition, the a6700 launched at $1,399.99. If you mainly need fast, reliable autofocus in a small body, the a6400 still does that.
In the hand with a Sigma 30mm F1.4 DC DN Contemporary. Photo: FBenjr123 via Wikimedia Commons, CC BY-SA 4.0 (resized)
The story
Sony Electronics announced the α6400 (ILCE-6400) on January 15, 2019, for February 2019 shipping at a suggested $900 body-only, $1,000 with the 16-50mm kit lens and $1,300 with the 18-135mm (Sony Electronics). Sony pitched it to "all types of creators ranging from professionals to vloggers".
DPReview's review (April 2019, 85% overall) praised its "industry-leading autofocus implementation" and image quality, and listed hit-and-miss ergonomics, no in-body stabilization, a UHS-I slot and rolling shutter among the drawbacks.
Key verified specs for the Sony a6400 (ILCE-6400), from Sony's US specifications page and Jan 15, 2019 release, and DPReview's review. Source for each row in brackets.
Fast Hybrid AF, 425 phase-detection + 425 contrast-detection points (about 84% of the frame); Real-time Eye AF, Real-time Tracking; EV-2 to 20 [Sony]
ISO
100–32000; expandable to 102400 for stills [Sony]
Stabilization
None in body; uses lens stabilization [Sony; DPReview]
Shutter / burst
1/4000s to 30s; flash X-sync 1/160s; up to 11 fps (Hi+), 8 fps silent; rated about 200,000 cycles [Sony]
Video
4K (3840 × 2160) up to 30p from full pixel readout, no binning; 1080p up to 120p; S-Log2, S-Log3, HLG; XAVC S [Sony]; 1.2x crop at 4K/30p, none at 24p [DPReview]
Viewfinder
0.39-type OLED EVF, 2,359,296 dots, 0.70x (35 mm equivalent) [Sony]
Screen
3.0-type, 921,600-dot touchscreen; tilts up about 180°, down about 74° [Sony]
Storage
One SD slot (UHS-I) [Sony; DPReview]
Ports / wireless
3.5 mm mic input (no headphone jack); micro HDMI; Micro USB with USB charging; Wi-Fi, Bluetooth 4.1, NFC [Sony; DPReview]
Battery
NP-FW50; CIPA about 410 shots (LCD) / 360 (viewfinder) [Sony]
Size / weight
120.0 × 66.9 × 59.7 mm; 403 g with battery and card [Sony]
Announced / price
Jan 15, 2019; $900 body-only at launch [Sony]
Sample photos
Six photos taken with the Sony a6400 by independent photographers, shared under Creative Commons licenses or CC0. Each caption names the lens. Select a photo to enlarge it. More samples from Sony
18mm, f/5, ISO 400, 1/60 s: dusk at Kerroch, Ploemeur, Brittany (Sony E 18-135mm F3.5-5.6 OSS). Photo: Allie_Caulfield via Flickr, CC BY 2.0 (resized)16mm, f/3.5, ISO 6400, 1/13 s: cherry blossoms at night (Sony E PZ 16-50mm F3.5-5.6 OSS, the kit lens). Photo: clvs7 via Flickr, CC0 1.0 (resized)
350mm, f/8, ISO 100, 1/640 s: barn owl in flight (Sony E 70-350mm F4.5-6.3 G OSS). Photo: John Knight via Flickr, CC BY 2.0 (resized)50mm, f/2.8, ISO 100, 1/400 s: outdoor portrait (Sony E 50mm F1.8 OSS). Photo: Lenky Chuột via Flickr, CC BY 2.0 (resized)
21mm, f/5.6, ISO 100, 1/80 s: a side street in Yokosuka (Sony E 16-70mm F4 ZA OSS). Photo: clvs7 via Flickr, CC0 1.0 (resized)18mm, f/9, ISO 500, 1/30 s: beach huts at Bridlington (Sigma 18-50mm F2.8 DC DN | Contemporary). Photo: John Knight via Flickr, CC BY 2.0 (resized)
Sony: Launched at $900 in 2019 (body only).
Verdict
If you want Sony's autofocus in a small, light body and can live without stabilization in the camera, the a6400 is still a sensible buy. Real-time Eye AF and tracking, 11 fps and the flip-up screen cover family, travel, street and casual video well.
It shows its 2019 roots in video and handling: no IBIS, a cropped and wobbly 4K/30p, one UHS-I slot and no headphone jack. Pair it with a stabilized lens, or spend up for the a6700 if you need IBIS and better video.
Pros
Real-time Eye AF and Real-time Tracking
11 fps with AF/AE tracking
Oversampled 4K, S-Log2/S-Log3 and HLG
Screen tilts up 180°; 403 g body
Cons
No in-body stabilization
1.2x crop at 4K/30p; pronounced rolling shutter (DPReview)
