Which records higher bitrates: FX3, FX6, or a7S III?

All three peak at 600 Mbps for UHD 4K 60p All-Intra. The FX6 uses XAVC-I (Intra); the FX3 and a7S III use XAVC S-I (also Intra). Storage per hour at 4K 60p All-Intra is identical across all three: about 270 GB. The FX6 adds XAVC-L Long GOP options that cut storage roughly in half at the cost of GOP-based compression.

FX3 vs FX6 vs a7S III for storage planning — which needs more cards?

At matching codec/resolution/fps, all three consume identical storage. For the same shoot at UHD 4K 60p All-Intra, all three need 270 GB per hour. The FX6's only storage advantage is XAVC-L Long GOP, which halves storage at the cost of GOP compression. Plan capacity the same way; choose the body for ergonomics.

Sony FX3 vs FX6 vs a7S III — Storage Comparison

Q: Which one has internal DCI 4K?

FX3 and FX6 record DCI 4K (4096×2160) internally; the a7S III does not. The FX3 records DCI 4K via XAVC S-I; the FX6 records DCI 4K via XAVC-I. All three record UHD 4K (3840×2160).

Q: Which has built-in ND filters?

Only the FX6. The FX3 and a7S III are mirrorless bodies without internal NDs. The FX6 is the only one with built-in electronic variable NDs (2 to 7 stops), making it preferable for daylight work where matte boxes are not practical.

All three share Sony's 10.3 MP back-illuminated full-frame sensor. All three peak at 600 Mbps for UHD 4K 60p All-Intra. For pure storage math, they're interchangeable — pick by form factor, NDs, and codec breadth, not by capacity.

FX3 shoot → FX6 shoot → a7S III shoot →

Storage at a Glance

	Sony FX3	Sony FX6	Sony a7S III
Peak bitrate (UHD 4K)	600 Mbps (XAVC S-I 60p)	600 Mbps (XAVC-I 60p)	600 Mbps (XAVC S-I 60p)
DCI 4K (4096×2160)	Yes, internal (XAVC S-I)	Yes, internal (XAVC-I 24p)	No
Card slots	Dual CFexpress Type A / SD UHS-II	Dual CFexpress Type A / SD UHS-II	Dual CFexpress Type A / SD UHS-II
Long GOP option	XAVC S, XAVC HS	XAVC-L (Long GOP) + XAVC HS	XAVC S, XAVC HS
4K 120p slow-mo	XAVC HS at 280 Mbps	S&Q (XAVC-L 4K 120p)	XAVC HS at 280 Mbps
Internal RAW	No (HDMI 16-bit RAW out)	No (SDI 16-bit RAW out)	No (HDMI 16-bit RAW out)
Built-in NDs	No	Yes (electronic variable, 2–7 stops)	No
Form factor	Mirrorless body	ENG body (top handle, XLR)	Mirrorless body
Storage per hour at UHD 4K 60p All-Intra	270 GB	270 GB	270 GB
Storage per hour at UHD 4K 30p All-Intra	135 GB	135 GB	135 GB
HD 120p All-Intra	100 Mbps (XAVC HS)	222 Mbps (XAVC-I)	100 Mbps (XAVC HS)

Bitrate-by-Bitrate Comparison

Same sensor means codecs and bitrates align almost exactly across the three bodies. The FX6's XAVC-L Long GOP modes are the main capacity advantage — roughly half the storage of All-Intra equivalents for similar visual quality at lower frame rates.

Setting	FX3 (XAVC S-I)	FX6 (XAVC-I)	a7S III (XAVC S-I)
UHD 4K 60p	600 Mbps	600 Mbps	600 Mbps
UHD 4K 30p	300 Mbps	300 Mbps	300 Mbps
UHD 4K 24p	240 Mbps	240 Mbps	240 Mbps
DCI 4K 24p	240 Mbps	240 Mbps	—
HD 120p All-Intra	100 Mbps	222 Mbps	100 Mbps
UHD 4K 60p XAVC HS	200 Mbps	—	200 Mbps
UHD 4K 120p XAVC HS	280 Mbps	—	280 Mbps
UHD 4K 60p XAVC-L	—	150 Mbps	—

Which Should You Pick?

a7S III — pick if you're a hybrid shooter (stills + video), already in the Sony Alpha lens kit, and don't need DCI 4K. Same recording pipeline as the FX3, two years older, usually cheaper used. Best low-light specialist in the lineup.

FX3 — pick if you need DCI 4K, a video-first body without a stills-camera viewfinder, and want compact mirrorless form for gimbals and travel rigs. Adds top handle with XLR audio module.

FX6 — pick if you need built-in NDs, integrated XLR, EVF, top handle, and Long GOP recording for long-form work. Heaviest of the three, but the only ENG-style body.

For pure per-hour storage at matching codec/resolution/fps, all three are identical. Plan capacity the same way; choose the body for the shoot's ergonomic and audio requirements.

Plan FX3 shoot → Plan FX6 shoot → Plan a7S III shoot →

Frequently Asked Questions

Do the Sony FX3, FX6, and a7S III use the same memory cards?

Yes. All three have dual slots that accept CFexpress Type A or SD UHS-II. CFexpress Type A is required for the highest-bitrate XAVC-I or XAVC S-I modes on each. SD UHS-II V90 works for most other modes on all three bodies.

Which records higher bitrates?

All three peak at 600 Mbps for UHD 4K 60p All-Intra. The FX6 uses XAVC-I; the FX3 and a7S III use XAVC S-I. Storage per hour at 4K 60p All-Intra is identical: about 270 GB.

Which one has internal DCI 4K?

FX3 (XAVC S-I) and FX6 (XAVC-I, 24p) record DCI 4K internally. The a7S III records UHD 4K only.

Which has built-in ND filters?

Only the FX6, with electronic variable NDs (2–7 stops). The FX3 and a7S III rely on external matte boxes or screw-in NDs.

Which one needs more cards for the same shoot?

None — identical per-hour storage at matching settings. The FX6's only capacity advantage is XAVC-L Long GOP, which halves storage at lower frame rates. For All-Intra recording, all three need the same cards.