Canon EOS R6 vs Sony a7S III — Which Is Better?

The Canon EOS R6 and the Sony a7S III are both full-frame mirrorless cameras released in 2020, so age favours neither. The lens mount comes first for most buyers: the R6 takes Canon RF lenses and the a7S III takes Sony FE lenses, so each body draws on its own native system. Neither mount fits the other's lenses directly.

The a7S III is the more compact body, measuring 129 x 97 x 81 mm against 138 x 98 x 88 mm for the R6. The R6 is lighter at 680 g, while the Sony weighs 699 g, a 19 g difference that leaves both bodies in the same carrying class.

The R6 is the stronger choice for heavy cropping and fast action stills. Its 20.1 megapixel sensor captures more pixels than the a7S III's 12.1, giving more room to crop a distant subject. Its maximum burst of 20 frames per second runs at twice the Sony's 10 for peak action moments. Its autofocus array is also denser, with 1053 points against 759.

The a7S III answers with a far sharper electronic viewfinder, at 9.44 million dots against 3.69 million on the R6, which helps when checking fine detail while framing. Both cameras offer in-body stabilisation, a 1/8000 second top shutter speed and a native ISO range topping out at 102400. The Sony also reaches lower ISO settings, at 80 native and 40 expanded.

Slow motion is a shared strength, with both cameras offering 120 fps as their maximum frame rate and both capping at 4K resolution. Fast action therefore holds the same top setting on either body, and the recording choice comes down to formats rather than capture limits.

The a7S III records in Sony's XAVC S and XAVC HS formats, while the R6 records MP4, so an editing pipeline built around either family points to one body. The R6 offers a built-in interval timer for timelapse, which the a7S III omits. Timelapse shooters get a simpler workflow on the Canon; videographers who need XAVC delivery get it on the Sony.

Both cameras give you a 3-inch touchscreen that flips out for waist-level and overhead work, plus weather sealing, Wi-Fi and Bluetooth for wireless transfer. Each supports an external flash, and neither has a built-in flash or GPS, so geotagging requires a phone or accessory on both.

The R6 gives slightly finer playback detail, with a rear LCD of 1.62 million dots against 1.44 million on the a7S III. That helps when reviewing focus or composition right after a shot.

The a7S III is the clear pick for long shooting days, with a battery rated for 600 shots against 360 on the R6. Both use their own batteries, the Canon LP-E6NH and the Sony NP-FZ100, and both support USB charging between sessions.

Both cameras have dual card slots. The a7S III adds a CFexpress Type A slot alongside SD UHS-II, giving heavy 4K recording a faster card option, while the R6 uses two SD UHS-II cards only. That extra card format benefits video work most on the Sony.