Sony FX3 Vs Sony A7S III - Wolfcrow

Why should anyone pay more for the Sony FX3 (Amazon, B&H) over the Sony a7S III (Amazon, B&H)? If you’re purchased the a7S III for video, did you make the wrong choice? Is it time to sell your camera?

Hopefully this article will help you decide which of these cameras is the better investment for you.

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Comparison of sensors and video features

It looks like the exact same sensor:

Camera	4K	Maximum FPS in 4K	Video ISO Range
Sony FX3	3840 x 2160 (4264 x 2408 RAW externally)	119.88p	80-102,400
Sony a7S III	3840 x 2160 (4264 x 2408 RAW externally)	119.88p	80-102,400

Both the cameras shoot up to 4K UHD internally. Both cameras will be equally good in low light.

Both does 240 fps in 1080p. Both have a 10% crop in 120p and 240p.

Camera	Dynamic Range	Max fps at 1080p
Sony FX3	15+ stops	240 fps
Sony a7S III	15 stops	240 fps

They are pretty much the same camera, aren’t they?

Overheating limitations

The Sony a7S III (Amazon, B&H) have overheating limitations in 60p and 120p. With the Sony FX3 (Amazon, B&H), Sony claims that it can record continuously at 4K 60p with no limit whatsoever.

However, Sony has slyly omitted any information on overheating when shooting 4K 120p.

In a nutshell:

• Up to 60 fps: The Sony a7S III overheats after about one hour of recording in ALL-I. No overheating with the FX3.
• At 120 fps: The Sony a7S III overheats after about 30 minutes of recording in ALL-I. We don’t have official figures for the FX3 but it’s going to be better due to the fan.
• Up to 30 fps: No problems with both cameras.

This one goes to the Sony FX3.

Dynamic range

Sony claims that the Sony FX3 (Amazon, B&H) fares better when you compare the dynamic range of the camera. I’m going to call BS on this one. Also, whatever minuscule image processing improvement exists isn’t going to make a tangible difference in the real world.

Both have the same codecs and color information:

Camera	RAW and Codec in 4K	Color Information for 4K
Sony FX3	16-bit RAW* | XAVC S-I 4K, XAVC HS 4K	RAW* | 10-bit 4:2:2/8-bit 4:2:0
Sony a7S III	16-bit RAW* | XAVC S-I 4K, XAVC HS 4K	RAW* | 10-bit 4:2:2/8-bit 4:2:0

The RAW isn’t truly 16-bit, and neither is the sensor.

You need the Atomos Ninja V for recording Prores RAW for both cameras. The “16-bit” RAW is converted to 12-bit Prores RAW through wizardry of the kind you don’t want to know about.

Focus and exposure aids, and ergonomics

What’s the point of RAW if you can’t expose it correctly? The little things make all the difference:

Camera	Exposure
Sony FX3	Zebras, histogram and in-camera meter
Sony a7S III	Zebras, histogram and in-camera meter

The Sony a7S III and the Sony FX3 are essentially the same camera as far as exposure aids are concerned, which is a shame.

This was an opportunity for the FX3 to pull ahead with a false color tool and waveform. Maybe it’ll come in a firmware update.

The S-Cinetone matrix is available on both cameras as of 25th February, 2021.

For best image quality I’d stick to S-Log3.

As far as size and weight are concerned:

Camera	Ergonomics	Weight
Sony FX3	Swivel monitor, tally lights, XLR grip with mounting threads	640g
Sony a7S III	Tilt and swivel LCD monitor	614g

You get an XLR module, tally lights and mounting points extra with the FX3. The mounting points are not always in a place that you’ll find useful.

Here’s how the differences make sense monetarily:

Camera	XLR Adapter	Cage and Top Handle	Combined Weight^
Sony FX3	$0	$0	1,015g
Sony a7S III	$150 (340g)	$106 (about 300g)	1,339g

To know more about the cage, read here:

The Best Universal Cage for Mirrorless and DSLR Cameras

You could also get the cheaper SmallRig cage but it doesn’t come with a top handle or side grip, and it’s for one camera only.

Price-wise, you can opt for cheaper XLR adapters like the ones from Wooden Camera or Beachtek. This gives you advantages not only in additional features, but you can also rig them the way you want. With Sony’s XLR hot shoe adapter and top handle, there’s only one way to go.

Weather sealing is not guaranteed on any of the cameras. Sony claims they have tried to make the cameras good enough to handle tough conditions. I don’t expect these cameras to be pushovers, and this is par for the course.

I’m not really a fan of the choices Sony has made here, for the FX3. It all seems rushed and not well though out. A “cinema” camera for YouTubers? What’s that?

Audio Features

Camera	Audio
Sony FX3	2x XLR/TRS 4ch 16-bit 48 KHz LPCM + 1x 3.5 mm jack (2ch)
Sony a7S III	1x 3.5 mm jack, 2ch 16-bit 48 KHz LPCM

The Sony FX3 (Amazon, B&H) comes with an XLR grip which can be attached to the top of the camera and be used as a top handle. The 2 XLR/TRS inputs with 4 channel 16-bit Linear PCM easily outclasses a7 S III’s single stereo minijack. But we can always add an XLR adapter, so it’s not like this is anything special.

Image Stabilization

Both the Sony a7S III (Amazon, B&H) and Sony FX3 (Amazon, B&H) have internal image stabilization (IBIS).

The Sony FX3 has gyro information, but to stabilize the footage you will have to use the Sony Catalyst software.

Timecode

Both the cameras do not have timecode input. They have in built TC/UB in the in-camera menu which will allow you to only sync the footage if you manually start all of your cameras at the same time and then line it up by timecode in post.

Batteries and media cards

Here’s a look at the media:

Camera	Dual card slots
Sony FX3	Yes, CFexpress Type A or UHS-II SD Cards
Sony a7S III	Yes, CFexpress Type A or UHS-II SD Cards

For the a7S III and the FX3, you need CFexpress Type A cards for the best codec (600 Mbps). But it’s the same.

What about battery life?

Camera	Battery life	Cost of one battery	Cost of 6 hours of operation
Sony FX3	95 minutes	$78	$312
Sony a7S III	90 minutes	$78	$312

You get 5 minutes extra with the Sony FX3. It loses an EVF but gains a fan. Not a practical difference in real world shooting.

Which is cheaper to own?

Let’s just add up the costs:

Camera	Sony a7S III	Sony FX3
Camera body	$3,498	$3,898
XLR, Cage and Top Handle	$256	$0
Zacuto Kameleon EVF Pro	$0	$1,950 (!!!)*
Total	$3,754	$3,898

There is a meager difference of about $144. The tally light is good for multi-camera setups, but you can always get something similar with the Imaging Edge Mobile app from Sony if you’re a one-person crew of vlogger or YouTuber.

So, what do you really get?

Before we take our final decision, we’ll let the cameras tell us what they offer that the other doesn’t:

Camera	USP	Major Cons
Sony FX3	Fan for no overheating, tally light	no EVF, overheating in 120p???
Sony a7S III	EVF, slightly cheaper, can take stills	Overheating in 60p.

My Verdict

For video, I’d pick the Sony FX3 (Amazon, B&H), and for one reason only – it doesn’t overheat. That’s it’s only killer feature.

On the other hand, if you’re not into longer record times, then nothing about the FX3 is compelling enough. Watch my Sony a7S III review:

Sony a7S III Review for Professional Cinematography

Those who purchased the a7S III will surely not be happy with the announcement of the FX3. That’s Sony’s cross to bear. They made the call.

Maybe they’re trying to corner the market that needs longer record times. These are mainly live streaming, events, religious services, documentaries, wildlife, sports weddings, etc.

Guess what? None of them are cinema-related. The Sony FX3 (Amazon, B&H) should have been the a7S III.

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