Canon EOS R5 vs. Sony A7S III – Film in 4k with 120fps or up to 8k
Last July was an important month in cameraland. The Canon EOS R5 was announced on July 9 and the Sony A7S III on July 28. Both cameras are top models in their class, with prices of 4200 and 4550 euros respectively. And both cameras are innovative, offering capabilities we’ve never seen before. The A7S III is all about video, although it has the same basic functionality as all other cameras in the A7 series. The EOS R5 is more of an all-round camera, being the new top model within the R-series, but especially notable for its advanced video functions, from 4k at 120fps to 8k.
In the video below, we look at how filming works in practice, whether filming in 8k already makes sense, what about the image quality and what problems we have encountered.
Specifications and improvements
What’s new with both cameras? The R5 has a 45-megapixel sensor, is capable of shooting 12 frames per second with a mechanical shutter and even 20 with an electronic shutter. Moreover, the biggest disadvantages of the EOS R have been eliminated; the camera now features built-in image stabilization that works with any lens, and there are two card slots.
While the R5 is an excellent stills camera, its video features are the most groundbreaking. As mentioned, it can film in 8k and also in 4k with 24 to 120fps. In 8k you can film in 12bit raw format with a bit rate of 2600Mbit/s. Compared to the EOS R, that’s a big step; that camera used a massive 1.7 times crop in 4k, which is the size of an aps-c sensor. The R5 uses the whole sensor. In the 4k HQ mode, raw 8k images are oversampled down to 4k, with a better quality. In all cases, a maximum recording limit of 29 minutes and 59 seconds. After that you have to restart the recording. With an external recorder there is no limit. The battery life has increased by fourteen percent thanks to the new Canon LP-EP6NH battery with 2130mAh. That’s less than Sony’s NP-FZ100 at 2280mAh,
The bit rate can be halved by recording in 10bit-4:2:2. The camera can also record 4k videos internally at 120fps. The images can be recorded in 12bit raw or with 10bit 4:2:2 c-log or hdr pq, using h265 compression. The electronic viewfinder has a resolution of 5.76 million pixels and a refresh rate of 120Hz. The native ISO range of the sensor goes from 100 to 51,200 and is digitally expandable to 102,400.
The Sony A7S III cannot film in 8k, but otherwise has similar specifications. This camera can also film in 4k with 24 to 120fps. Internally, recording in 10bit with 4:2:2 encoding is possible in Sony’s XAVC S and XAVC HS formats, which are based on h264 and h265 with bit rates of 600 and 280Mbit/s respectively. Via the HDMI 2.1 connection, it is possible to output raw video in 16bit. With many high-end cameras, this is a maximum of 14bit via HDMI. On the other hand, it is not possible to record internally in raw format.
The camera gets a new Bionz XR image processor and now finally also has phase-detection points, just like other cameras in the A7 series. The ISO range of the sensor is from 80 to 102,400 and can be digitally expanded to ISO 40-409,600. The sensor is equipped with five-axis image stabilization. The resolution of the sensor is still 12 megapixels, which almost seamlessly matches the 4k resolution in 16:9 ratio.
The electronic viewfinder now has a whopping 9.4 million pixels, which is the highest number we’ve seen to date. Furthermore, the camera is now equipped with a fold-out and tiltable screen, which has great added value for video. There is also now a full HDMI port, which is practical, but also much less vulnerable than a mini or micro HDMI cable. Finally, the memory slots have been expanded.
Compactflash express
Both cameras can still handle SD cards, but focus mainly on the faster compact flash express, albeit each in its own way. The original EOS R only has a single SD card slot, but the R5 has added a second slot. It is a cf-express type b, where cf refers to compactflash, of which this card is the successor. CF-express type b is a large and sturdy card that is physically almost the same as xqd memory, which is used in Nikon cameras, among other things. For higher resolution or high fps video modes it is necessary to use cf-express as its write speed is much higher. This applies to 8k-raw, 4k 120 all-i, 10bit-4:2:2, 4k all-i hevc and 4k 60 all-i. CF-express offers write speeds from 1 to 8 GB/s, at least in the future. The speed is linked to the number of PCI-express lanes and that is currently stuck at two, which is good for a theoretical maximum of 2GB / s. So in many cases you need cf-express memory instead of sd.
Until now, Sony used SD cards in its cameras, but CF-Express has now been added. Sony does not use type b, like Canon, but type a. Type a is a lot smaller, slightly smaller than sd, and therefore takes up significantly less space. Given the similarities with SD, Sony has made the slots suitable for both types of memory. So you can use two sd cards, two cf-express or a mix of both. The smaller size and the interchangeability with SD cards are therefore advantages. A disadvantage is that type a is slower than type b, because only a single pci-express lane is available. The maximum theoretical read speed is therefore 1GB/s. Another important difference between Sony and Canon is that on the A7S III it is possible to record on two memory cards at the same time, which is useful as a backup. CF-express type a is only necessary for 4k 120 in the ‘slow and quick’ mode, the rest can also be done in sd. CF-Express type A cards are also horribly expensive at the time of writing.
Ergonomics
Of the two cameras, the Canon feels better in the hand. The camera is a bit larger, but also has a deeper grip. The grip of the Sony is larger than with the earlier A7S models and also easy to work with, but the Canon is just a bit more pleasant. At the top, the R5 looks much the same as the EOS R, with the signature monochrome screen and video button. At the back are now a dial around the set button and a joystick. We’ve known them for a while from Canon’s DSLRs and they’ve now also found their way into the mirrorless series. That works a lot more pleasantly than the touch-sensitive button on the EOS R.
The A7S III resembles its predecessors like two drops of water, with the aforementioned fold-out screen as an important improvement. Also new is that the video button is now on the top, within reach of the index finger. That is a more logical position, which also leads to less vibration when switching a recording on and off. If you are recording, you can now clearly see this on the screen with a large red frame around it. The screen is touch sensitive and can now finally also be used for the menu. The menu itself has also been overhauled and laid out a lot more logically, more similar to the way Panasonic and Nikon do it. This also takes some getting used to, but because there are more main sections with clear icons, you will find what you are looking for sooner.
The utility of 8k
What can you do with 8k video in 2020? Little by little we see more and more 8k TVs and monitors, but they are still scarce. One day it will become the new standard, so content that you shoot in 8k now can be viewed in its full glory once 8k media is brought home. Still, filming in 8k can already be useful now. For example, you can film in 8k to get a 4k crop from it, something many youtubers now use with 4k and 1080p. With 8k you can zoom in twice digitally to get to a 4k resolution and it is also possible to do a virtual panscrolling from left to right. You can also use 8k images to extract stills, or photos, provided that the shutter speed is taken into account. After all, 8k equals thirty images of 35 megapixels each. This can be especially useful for capturing action to grab exactly the right moment. Finally, it is useful to use the 8k source material to convert it back to 4k in order to achieve a sharper end result. This is exactly what Canon does in 4k HQ mode and the result is impressive. The advantage of filming in 4k HQ is that you get a better end result and you don’t have to save and convert the large 8k files yourself. Finally, there is another reason for the real video nerd to film in 8k; you can downsample 8k 4:2:0 to a perfect 4k 4:4:4.
Filming in 8k with the EOS R5 also has its challenges. First of all, you need a lot of storage and the compact flash express cards are expensive. The 64GB card that we could borrow from Canon was already full after 6 minutes of filming. Cards of 256GB or larger are therefore a must. Editing and rendering 8k images requires a lot from computers. Our iMac Pros with 10-core Xeon processors and Radeon Pro Vega GPU had a hard time with it, although Adobe Premiere may also play a role. The biggest bottleneck, however, is that the R5 gets very hot during filming.
Overheating
Immediately after the start of our tests, we found that the camera in 8k and 4k120 got hot very quickly. When filming in 8k, a flashing overheating warning popped up after just over 10 minutes, and within 15-20 minutes the camera turned itself off saying it was too hot and needed to cool down. We were soon one to two hours further before we again had the full recording time at our disposal.
At the end of August, a firmware update, v1.1, appeared that improved but did not solve this problem. The useful life is now approximately forty percent longer, which in itself is a significant improvement. In our tests, a warning now appeared after about 18 minutes with an 8k recording and the camera shut down after 24 to 27 minutes. In 4k-HQ it was 35 to 39 minutes. That includes restarting after reaching the 29m59 recording limit and formatting the cf-express card if it was full.
The significant increase in recording time makes filming a lot more flexible, but the cooling problem remains. Although the camera has been able to start filming more quickly since the firmware update, in practice it is limited to short pieces. Long takes or many takes in a row can be a problem. In addition, every use of the camera counts. Shooting and using the menu also affect the available movie length. If you mainly use the camera for photography and you don’t film for too long in a row, the R5 is perfectly usable, but it will make do for serious video productions. It seemsthat the image processor, sensor and the CF-Express memory card become very hot; after the firmware update, the temperature has risen a little further. Incidentally, the recording limit is also related to an artificial timer, which keeps track of how long it has been recorded. There are methods to work around this, but it is not recommended.
Overheating was also a problem for a long time with Sony, but this has improved enormously with the A7S III. In none of the modes have we encountered any problems in practice. During an endurance test we ran into 4k with 120fps after an hour and 15 minutes of overheating and not in the other modes. In a tropical climate this may be different.
Image quality
When we look at how the cameras perform in practice, we see many similarities and some differences. The 120fps mode in 4k is ideal for making slow-motion videos. Both cameras do that very well and that quickly produces impressive results. We did not really see any clear differences. What does differ is that the Sony is also capable of capturing 240fps in 1080p. The effect is therefore even greater, but you sacrifice a lot of sharpness for it. An inconvenient point with the Canon is that you cannot choose 120fps directly, but first have to switch on the high frame rate setting.
For our stabilization test, we mounted the cameras side by side on a bracket to compare the result one to one. We usually deliberately filmed handheld to see how well that went. A gimbal obviously produces better results. Both cameras have two stabilization modes and the EOS R5 performs well and consistently. This was not the case with the Sony; we saw smooth movements one moment, then sudden jerks a few seconds later. That was clearly less than we were used to from other cameras from the A7 series. We used a pre-production model and according to Sony, this issue is known and fixed in the final firmware. We trust that this is true and that it performs at least as well as other recent A7 cameras.
In low light and high ISO settings, the Sony is clearly the winner. For our test, we started at ISO 1600 and moved up a few steps, all the way up to ISO 40,000. The image of the A7SIII is clearer, more detail is visible and there is significantly less image noise.
What both cameras have a pretty good handle on is rolling shutter . For Sony in particular, this is a major improvement over previous A7-series cameras. This means that you suffer a lot from this effect, which causes distortion of straight lines during fast movement because the sensor is read too slowly from top to bottom. That can be a serious limitation when shooting your production. However, the lines of the parking garage in our video remain nice and straight and to be honest you can expect that for this money.
Sony has always been lord and master when it comes to eye autofocus. Canon has now expanded that functionality and is therefore almost at the same level. Sony’s is sometimes even more accurate, recognizing an eye from a slightly greater distance and focusing on it.
| Canon EOS R5 | Sony A7S III | |
| Sensor resolution | 45Mp | 12Mp |
| 8k | 24,25,30 | – |
| 4k | 24,25,30,50,60,120 | 24,25,30,50,60,120 |
| 1080p | 24,25,30,50,60 | 24,25,30,50,60,120,240 |
| Off points | 1053 | 759 |
| Photoburst | 12/20 | 10 |
| native max iso | 51,200 | 102,400 |
| EVF magnification (dots) | 0.76x (5760k) | 0.91x (9440k) |
| LCD screen (dotted) | 3.2″ (2100k) | 3″ (1440k) |
| Coloring room | 12-bit raw / 10-bit 4:2:2 | 12-bit raw / 10-bit 4:2:2 |
| HDMI | Micro | Full size |
| Storage | 1x cf-e a, 1x sd | 2x cf-e b, 2x sd |
| Weight | 738g | 699g |
| Scope | 138x98x88 | 129x97x81 |
| Ibis | Yes | Yes |
| Top LCD | Yes | no |
| Fold-out + tiltable screen | Yes | Yes |
| Headphones+mic | Yes | Yes |
| Touch screen | Yes | Yes |
Conclusion
Both cameras are innovative and offer possibilities that we have not seen before in this camera segment. From a video point of view, the Sony A7S III is a camera that is much better suited for this. Unlike older models, it hardly suffers from overheating, has no recording limit of half an hour and the battery lasts a relatively long time.
The video specs of the EOS R5 are extremely interesting on paper, and to be honest, it’s a great achievement from Canon to achieve this. We should not forget that the R5 is aimed at both photography and video. If you mainly shoot photos and film short videos at most, the R5 is an excellent all-rounder. But for serious video work you quickly run into limits. You can film unlimited in 4k with 24fps, but above that you will soon suffer from overheating. Apart from the limited recording time, the problem is that the camera then has to cool down before you can continue. For serious film work, this is usually not really workable in practice and can therefore be a deal breaker. Reasoned from someone who mainly takes photos, the extensive video options are a nice extra and less of a limitation.
In any case, both the EOS R5 and the Sony A7S III have raised the bar for video again. We give the Sony an Excellent award for the excellent performance in practice and we give the Canon an Innovation award for the new possibilities, such as filming in 8k. In other words: work to be done for the other camera manufacturers.