Sony RX10 III vs RX10 IV – Which is For You?

The lower down the digital camera food chain you go, there more churn there is in models; compacts are replaced yearly, while enthusiast DSLRs and CSCs take longer. Pro cameras are replaced maybe three times a decade. Take Sony’s RX10 digital compact series for example. It’s been routinely updated since the first RX10 arrived in early 2014, when Sony brought together a large (for a compact) 1in sensor and long zoom in the same body. The series has been well received throughout, offering decent image quality and lots of versatility. The latest offering is the RX10 IV, announced in the Autumn of 2017, but with the RX10 III only a little longer in the tooth, what has changed, and is it worth forking out extra for the new model? Let’s find out…

In terms of looks and handling, there are only minor differences between the two models.

Image quality

Both the III and IV use a 1in (13.2×8.8mm) back-side-illuminated (BSI) CMOS sensor, giving an effective 20 megapixels and a largest file size of 5472×3648. That’s plenty for printing up to A3 prints without interpolation. Images can also be shot in 1:1, 4:3 and 16:9 aspects. Using BSI technology and having a stacked (Exmor RS) design, the sensor records a purer signal, faster and therefore gives excellent image quality, detail and speed for its size. More on the benefits of the stacked sensor in the performance section.

ISO range is identical, too. It spans 100 to 12,800, but can be pulled to 64 and 80, and pushed to 25,600 if required. Plenty of versatility there, even if you can’t expect the same performance as on larger sensors. Broadly the BIONZ X image processor does a grand job of reproducing colour and detail on both.

Both cameras boast a 24-600mm equivalnet 25x zoom lens making them incredibly versatile.

Design & build

The RX10 III and IV’s big pitch is that they allow a huge range of focal lengths in a comparatively small body. Both feature a 24-600mm equivalent telezoom lens giving a 25x zoom function. The lens has a variable aperture, but it’s not too sluggish, falling from f/2.4 at the 24mm end to f/4 at 600mm. Both models can also employ a digital zoom taking you to an effective 100x, but quality will fall the further you push it.

In both cases, you can focus manually if desired and you can shoot as close as 3cm from the end of the lens. To combat camera shake at such long focal lengths both cameras offer optical image stabilisation rated at 4.5stops.

In terms of body style there’s not much to call between the two either. Both cameras have a large DSLR style grip, with the body being made of a magnesium alloy and composite plastic. It adds up to a decent build quality, and on both models there is a degree of weather sealing to fend off rain, moisture and dust.

Weight and dimensions are very close again. The RX10 III is fractionally lighter at 1051g including battery, versus the IV’s 1095g; in dimensions they are virtually identical at 133x94x127mm.

When it comes to the cameras’ screens and EVFs there’s little difference again. Both use a 3in tilting screen, but the IV has added touch controls and improved the resolution a little; there’s a lift of 1,228,800 to 1,440,000 dots. The EVFs are identical, both having a 0.7x magnification, 2,359,296 dot resolution and 100% frame coverage.

The Sony RX10 IV has a higher resolution LCD which also allows touch functions.

Features & handling

Both the RX10 III and IV have a shutter speed range of 30secs to 1/2000sec, but in either case this can be quickened using the electronic shutter, to 1/32,000sec. Bulb mode is also available. Exposure compensation is rated at +/-3EV on both models. And both have a built in pop-up flash, as well as hot-shoe to fit accessories.

In terms of button layout the main changes are the addition of an AF-A step on the focus lever and a focus limiter switch. A single SD card slot is used on both cameras.

Something to note on both models is the use of three programmable rings on the lens barrel that can control zoom, focus and aperture. There’s also a handy Fn button on the side of the lens that can be remapped.


Here things get more interesting. It’s in shooting speed and AF performance that the main differences between the III and IV are to be found, with many of the IV’s improved specifications borrowed from the recent RX100 V. These improvements come partly from the use of a stacked sensor design, upgraded from the previous version, but still using a DRAM chip to increase processing speed and provide faster frame rates and focusing speed (as well as quicker exposure calculation).

Starting with continuous shooting, there’s a hefty increase from 14fps on the III to 24fps on the IV. Things are even more impressive when you consider that the IV offers full AF and auto exposure at that pace; to use those features on the III the speed would slow to 5.5fps. On the IV, this can be tempered using three Continuous speeds (Hi, Medium and Low).

AF improvements are perhaps even more marked and hint a split in users for the new model. The III used a 25 point contrast-detect system, but this has been uprated to a 315 point phase-detect system on the RX10 IV (the 25 point contrast-detect system can still be used). The number of points and speed of calculation allows improved performance in modes like subject tracking, too.

There’s also a new AF-A mode which automatically switches between the single and continuous modes depending on the subject and a new Focus Area Recognition mode which allows you to map particular focus areas to a button, speeding up focusing. Making use of the new touch screen, the IV also lets you change focus points using that.

Two small changes to the left side of the body; there’s an AF-A function added to the AF mode lever, and a focus limiter.

Video & other features

Both cameras have lots to shout about in terms of video features. Each offers 4K (3840×2160) at up to 30p and Full HD at an impressive 120p. There’s even more pace in the shape of a high-speed mode (HFR) that can shoot up 1000fps (960fps in NTSC format) for slow motion effects. These processor hungry high speed modes can be shot in quality- or speed-priority modes, and here there’s another uplift for the IV; in quality mode, you can shoot for 4secs rather than 2secs, and in speed mode you get a similar increase, from 4secs to 7secs.

For serious video users, both models have a wealth professional modes: Picture Profile, S-Gamut/S-Log2 (S-Log3 on the IV), clean HDMI output, TC/UB, REC Control, Dual Rec, Marker, Gamma Display Assist and enhanced Zebra functions. Going back to AF for a moment, the improvements continue in video mode, with performance, according to Sony, being twice as fast.

For improved audio and sound monitoring, there are mic and headphone sockets on both cameras, as well as a Multi/Micro USB Terminal, Hi-Speed USB (USB2.0) and Micro HDMI.


Both the Sony RX10 III and IV offer an excellent blend of image quality, build, performance and versatility. It’s the speed and AF performance of the IV that really sets it apart, so a purchase should based on whether you need faster frame rates and improved focusing speed and accuracy.

The improved performance is worth the upgrade price, but only if you really need it.

Sony RX10 IIISony RX10 IV
Price$ 1,469.00$ 1,709.00
Sensor20.1-Megapixels BSI CMOS20.1-Megapixels BSI CMOS
ISO100-12800 (64-25600)100-12800 (64-25600)
LCD1,228,800 dot 3-inch vari-angle1,440,000 dot 3-inch vari-angle touchscreen
Image stabilisation
Max Burst rate12fps (5.5fps with AF and AE)24fps
4K video
Dual card slotsXX
Aufocus points25315