Upgrading the S1R and S1H cameras to use CFexpress cards improves card intake speeds by about 1/7th. Its, frankly, a little disappointing, but not surprising. When Panasonic allowed for the use of CFexpress cards in its flagship cameras via a firmware update, many had visions of multiplying data throughput – which indeed is theoretically possible when looking at the CFexpress standard. But there are many, many variables that affect actual throughput, including the camera’s firmware and the hardware and software built-in to components of the bodies that usher the data onto the card. There are so many variables, that after talking to engineers and executives at several CFexpress manufacturers, we stopped keeping track of them and opted instead to just acquire and test the cards to show real-world performance.

The Panasonic S1R and its husky brother, the video-oriented S1H, are limited to just below 10 frames per second in terms of image acquisition, and that won’t change with a faster card, but what will change is the behavior of the camera once the cache is filled up. The cameras start a significant slowdown of framerate after six seconds into a burst. The excellent camera site Imaging-resource.com provides some independent testing of these sorts of things, as we corroborated their findings both with a recent rental, as well the author of this research piece having used the S1R as his primary shooter for most of 2019. With those 62 shots taken before the cache fills, the cameras take about 17 1/2 seconds to finish packing the data stored in the cache onto an XQD card. With upgraded firmware and the addition of any of the fastest CFexpress cards available, that time to pack the data away lowers to 13 1/2 seconds.

In the days of XQD cards, trying to continue to shoot with a full buffer would only offer a photographer 2.5 frames per second. With the CFexpress card enabled, that buffered shooting rate now becomes 2.8 frames per second.

Frames/:30 (Blue) and Seconds to Clear Cache (Green)

It appears that there are hardware and/or software limitations still in the Panasonic data path separate from the speed of the cards. The cards have been extensively tested with the Canon EOS R5 and R6 to show greater absolute capability, as the link above and chart below show. The five fastest-rated cards tested all took more than 300 shots in a 30-second period on the Canon R5, and showed a framerate with a full cache of 9.9 frames per second (versus the 20 frames per second the camera was set to do in electronic shutter mode during that test).

That 9.9 frames per second (FPS) moving onto the CFexpress card in the R5 compares directly with the 2.8 frames per second moving onto the same card in the Panasonic S1R, a more than three-fold difference. Below is a chart of available CFexpress cards showing how many seconds each takes to clear the R5 buffer, which is a similar size to that of the Panasonic S1R. For one of the fast cards, the average is about 4 seconds, compared to the S1R’s CFexpress buffer clearing of 17.3 seconds using XQD and 13.5 seconds using CFexpress.

Seconds to Clear Similar Buffer in Canon EOS R5

We have seen this card format software dance before. When the UHS-II standard became available, a few cameras received upgrades to firmware allowing the new cards’ use. In no case did those upgraded cameras fully exploit the new speeds available with the new card standard, as some combination of other components provided data bottlenecks.

Which Card is Best?

The ProGrade Cobalt cards appear to show the best performance and decent price, but the differences in performance on the Panasonic bodies are very slight versus the differences seen on the Canon (and even Nikon) bodies, where there appear to be fewer bottlenecks. Within the margin of error at the top are also the Angelbird Pro XT card and the Delkin Power card. Sony’s Tough card performs just as well, but is more expensive. Transcend and the ProGrade Gold cards performed measurably, but slightly less well.