The EOS R5 was one of the hit cameras of 2020, and now Canon have followed up on that success by launching a new flagship mirrorless camera called the EOS R3.

At first glance you'd be hard-pressed to tell it apart from the same company's range-topping DSLR camera, the EOS-1D X Mark III, and indeed the Canon R3 mirrorless and the 1D X III DSLR actually share quite a lot of similarities, so which one should you pick?

We're bringing you this in-depth Canon R3 vs Canon EOS-1D X Mark III head-to-head comparison to help you choose between these two flagship 35mm full-frame cameras.

You can also read our detailed Canon EOS R3 review and Canon EOS-1D X Mark II review to find out exactly what we think of each one.

Sensor and Processor

The EOS-1D X Mark III has a 20.1 megapixel full-frame CMOS sensor and the very latest DIGIC X image processor, a combination that's built for speed.

The R3 ups the ante considerably, though, by being the first ever EOS camera to use a Stacked, Back-Side Illuminated (BSI) CMOS sensor in combination with the same DIGIC X processor.

The new 24.1 megapixel stacked sensor potentially promises better low-light performance at like-for-like ISO speeds and faster performance than the conventional CMOS sensor used by the EOS-1D X.

ISO Speed

The native sensitivity range of the Canon EOS-1D X Mark III runs from 100-102,400, which can be expanded to ISO 50-819,200.

The ISO range of the Canon R3 is ISO 100 to ISO 102,400, which can be expanded to ISO 50 to ISO 204,800, so not as wide as the EOS-1D X Mark III.

Video

The 1DX Mark III is capable of internally recording DCI 4K video at 60 fps with 10-bit 4:2:2 color and Raw 5.5K video, plus there's also Full HD recording up to 120fps.

The Canon EOS R3 offers an improved 6K/60p internal recording due to the 24 megapixel sensor that it uses, in addition to 4K video at up to 120p. And impressively Canon are promising that the R3 can record up to six hours of regular video or 1.5 hours at high 119.88/100p frame rates.

Autofocus

The Dual Pixel CMOS AF system that's used on the 1D X III when shooting video or in Live View features 3,869 autofocus points with 525 automatic positions.

The new Canon R3 uses a "next generation" version of Dual Pixel CMOS AF, which offers better tracking and focusing than any other EOS camera to date, including the 1D X, no mean feat given that camera's superlative focusing system.

There's also a brand new vehicle tracking mode, which allows you to expertly track motorbikes, open cockpit Formula cars as well as GT and rally cars, and even has the ability to prioritise the vehicle or the driver’s helmet!

It's also resurrecting the innovative eye-control AF function from the 1990's era EOS 3, 5 and 50 film SLRs. This allows you to select the AF point simply by looking at it through the viewfinder!

Burst Shooting

The Canon EOS-1D X Mark III can capture images at up to 20fps in live view or 16fps with the viewfinder and the buffer allows Raw and JPEG bursts of up to 1000 frames.

If you want even faster burst shooting, the Canon R3 takes things to a whole other level by being able to shoot at 30fps with the electronic shutter with full AF/AE tracking and minimal image distortion.

On a more negative note, the R3 can only shoot at 12fps using its mechanical shutter, versus 20fps on the 1D X.

Weather Resistance

The Canon R3 will feature the same professional level of durability and dust and moisture resistant weather-proofing as the EOS-1D X Mark III DSLR.

Integrated Grip

The Canon R3 shares the same integrated grip design with duplicated vertical controls that EOS-1D series users have enjoyed for many years.

Whilst pro shooters will mostly be delighted, enthusiasts may find the extra bulk and the lack of flexibility more off-putting.

IBIS

The Canon EOS-1D X Mark III doesn't feature an in-body stabilisation system, instead relying on the lens to supply it if available.

The new R3 offers the same IBIS system as the EOS R5 - its 5-axis In-Body Image Stabilizer can combine with the optical Image Stabilizer in selected RF lenses to offer industry-leading performance worth up to 8-stops - giving Canon a significant advantage over the EOS-1D X Mark III.

LCD Screen

The Canon EOS-1D X III has a a 3.2-inch 2.1m-dot LCD touchscreen that's fixed in place.

The EOS R3 has a much more versatile vari-angle touch screen which provides greater flexibility of shooting angles thanks to its ability to tilt and rotate into a range of positions, unlike the fixed screen on the EOS-1D X III DSLR camera. And it's much higher-resolution too - 4.1-million dots to be exact.

Memory Cards

The Canon EOS-1D X Mark III has dual memory card slots, both of which support ultrafast CFexpress cards.

The Canon R3 has one UHS-II SD card slot and one ultra-high speed CFexpress slot, so it doesn't follow the lead of the EOS-1D X Mark III which has two CFexpress slots.

Battery Life

The EOS R3 uses the LP-E19 series battery from the EOS-1D X III, rather than the LP-E6NH series that the EOS R5 uses, which provides up to 620 shots when using the viewfinder and 860 shots when using the LCD monitor.

Price

The EOS-1D X Mark III retails for £6,4999 / $6,499 in the UK / US, a price-tag that is also shared by the Sony Alpha 1.

The Canon EOS R3 is priced at £5,879.99 / $5,999.00, so it's commendably cheaper than the EOS-1D X Mark III at launch.

Conclusion

The new Canon R3 and the both 1D X III both share a similar, familiar visual profile with their integrated vertical grips, so it's going to be fascinating to find out how the mirrorless model either matches or even surpasses its DSLR equivalent.

It seems that Canon are taking things to another level with the R3, especially thanks to the BSI sensor, 6K video, vari-angle screen, 8 stops of IBIS, 30fps burst shooting and an even more sophisticated auto-focusing system than the already pretty incredible 1D X.

So what do you think? Would you choose the new Canon R3 mirrorless or the Canon EOS-1D X Mark III DSLR, and why? Leave a comment below!

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