Sony α7S III: Internal 4K 10-bit, External 4K 16-bit


Sony’s new α7S III continues to blur the boundaries between still and cine cameras. Not blurred, of course, are its images and the trajectory of thoughtful innovation inside.

Some quick specifications of the new α7S III:

  • 12 MP resolution, 4264 x 2814 3:2 (1.5:1) 36 x 24 mm sensor.
  • ISO 80-102,400. (40-409,600 extended.)
  • 15+ stop dynamic range in S-log3.
  • 10-bit 4:2:2 internal recording to Cfexpress type A and SD media
  • 16-bit external recording via full-size HDMI connector
  • 4K full pixel readout in all modes. No crop.
  • SLog 2, SLog 3

Preliminary Details

Here is a preliminary description based on a discussion with Sony’s incomparable Mark Weir. He was incomparably patient with my questions and articulate in explaining complex theories understandably. A more complete report will follow in the next edition of FDTimes. But meanwhile:

The α7S III launched at 10 am EDT, Tuesday July 28. It is the latest in Sony’s alpha series of hybrid still/cine E-mount Full Frame cameras. Think of “S” for “Sensitivity,” “Speed” (as in high ISO) or “Almost See in the Dark.” It’s hard to believe that its predecessor, α7S II, arrived 5 years ago and the original groundbreaking α7S was at NAB 2014.

By the way, you can remember what “R” stands for in the alpha series: “Resolution,” as in 61 megapixels within the α7R IV delivered last September.

The α7S III will record 4K QFHD Full Frame internally to Cfexpress type A memory cards up to 120 fps.

The camera will capture Full Frame 4264×2408 16-bit RAW 4K DCI up to 60 fps and output to an external recorder via its full-size HDMI type A connector.

A separate announcement arrived from Atomos at 10:09 am EDT. Atomos Ninja V will get a firmware update around September 2020 to record 4Kp60 ProRes RAW over HDMI from the α7S III. The α7S III 16-bit Linear RAW will be compressed and recorded as 12-bit Log RAW on Ninja V. 

EVF and Sensor

You will be impatient to put eye to eyepiece of the α7S III because it has a QXGA 9.44 million dot OLED electronic viewfinder. That could exceed the quality of many optical groundglass finders.

There’s an all-new, 12 Megapixel Exmor R CMOS sensor inside the dust and moisture-resistant, ventless and fanless camera body. Some people call it back-illuminated, which is kind of weird since the light is not coming from the rear of the photosites. Mark prefers to call it “reverse structure” because the wiring is positioned behind the photodiodes.

The new sensor provides phase detect auto focus, something new in the α7 series. It’s similar to the autofocus phase detection of the α7R IV and α9. The promise is very fast autofocus, real-time eye AF, rack focus, subject tracking, touch tracking and smooth focus transitions.

So, you might ask, if this camera’s sensor is a “mere” 12 Megapixels while you can count up to 61 pixels on other models, why is that so interesting?  In short: 4K, Full Frame, full width video, 15+ stops dynamic range, crazy high ISO, low noise, minimized rolling shutter effect, faster readout and higher fps.

The long answer is in the math. The 12K sensor’s photosites are arranged in a 3:2 ratio of 4264 x 2814. That means the 4K full-width image uses all those big pixels without binning, cropping or scaling. Although official photosite size is not given, you can divide sensor width in mm (36mm) by number of pixels (4264) and you get about 8.5 microns.

Record 3 formats internally, up to 4K QFHD (not DCI 4K).

No 29 min 50 sec limit. Up to 60 minutes 4k / 60p per specs but in actuality might record several hours.

  • XAVC-S Long-GOP (inter-frame) h.264 mpeg4 3840 x 2140
  • XAVC-HS Long-GOP (inter-frame) h.265 HEVC
  • new XAVC-SI (all intra h.264) up to 600 Megabits/second with frame rates up to 120 fps in 4K and 240 fps in Full HD

Additional Details

Compared to the previous model, rolling shutter is minimized by 3x, sensor readout speed is increased 2x and computing power of the new Bionz XR image signal processor is improved up to 8x. This means better sensitivity, greater signal-to-noise ratio and hence, less noise.

The OLED EVF has 0.90x magnification and 41 degree field of view with a 25mm high eye point.

There’s a menu setting to reduce the field of view to about 35 degrees and approximately 35mm high eye point.

A fully articulating monitor swings out on left side of camera. It has touch menu control and an all-new menu layout. The menu has been revised with a more intuitive 3 column layout. Submenus on the right show 2 additional levels of choices.

There’s a new Still or Video menu mode accessed by the dial on top to limit menu settings so they are unique to each and to keep your choices uncluttered.

This is Sony’s first camera with Cfexpress type A memory cards. These cards achieve 700 Mbps write / 800 read speeds. They will come in 80 or 160 gb capacities. They are smaller than Cfexpress type b and SDXC cards. There are two slots in the camera and each slot accepts both types of cards. Cfexpress type A media cards will be released around the same time as this camera.

As with the other α7 and α9 cameras, this one also has an E-mount: 18mm Flange Focal Depth, 46.1 mm I.D. There are currently 57 E-mount lenses from Sony and many more from SIGMA, ZEISS and others. And, of course, there are many E-mount to PL, LPL, M, PV, and adapters.

IBIS offers 5 axis In-Body Image Stabilization.

Dust and moisture resistance have been improved. There is no internal fan. A new method of heat dissipation lets you shoot 4K 60p for more than an hour. A lack of vents means that moisture resistance is increased.

The α7S III will be available in September 2020 for about $3500- 4000.





Leave a Comment

Tags: ,