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If we take a look at SD cards, we've had the UHS-II standard for a few years now which can allow writing at 300+ Mbps. However only a dozen cameras currently support it, with most using UHS-I at most. Canon and Nikon also support CF, XQD, and CFast cards for their very top models, but most of their range lacks any options for truly fast data writing. As a result you're limited by your buffer size, which must be extremely annoying for anyone who's trying to shoot a large burst of pictures. Writing at 300 Mbps on the other hand can easily allow continuous shooting at 10 FPS in RAW for as long as you can possibly need.

So what's the reason for being so slow in adapting proper card standards? Is it so the manufacturers are able to force photographers to buy their top-shelf products? Or perhaps people like sports photographers just shoot in JPEGs and therefore don't care about the card speeds?

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  • \$\begingroup\$ Are there really so much cameras that 1) are out several years after the new card standards and 2) do stall down frame rates significantly with even the best cards of their supported standard? \$\endgroup\$
    – PlasmaHH
    Oct 8, 2017 at 14:38
  • \$\begingroup\$ @PlasmaHH my brand new Canon 200D tops out at 1.5 fps when shooting in RAW with the best card on the market. \$\endgroup\$
    – JonathanReez
    Oct 8, 2017 at 14:40
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    \$\begingroup\$ Well, the 200D isn't exactly high end, I would not expect canon to spend much on getting a really fast card slot into it. You are already writing with probably about 50MB/s which I think is a reasonable speed for a camera at that price class and with an entirely different design goal. Also remember that UHSII and up requires entirely different sockets, which probably not many are willing to spend. You will see however that cameras where FPS plays a role in the design will have fast card support. \$\endgroup\$
    – PlasmaHH
    Oct 8, 2017 at 14:54
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    \$\begingroup\$ This puzzles me but it is possibly a technology or cost limit. Case in point, many cameras that actually accept a UHS-I card on one slot, do not support it one the second! This means there is either added costs that is considered not worth passing to the customer or the throughput to feed the cards is difficult to achieve. \$\endgroup\$
    – Itai
    Oct 8, 2017 at 15:26
  • \$\begingroup\$ @Itai might be a RF design (you need to route your wiring with more care) or power consumption (faster electronics need more power) issue ... but it might be also a good way to get rid of last generation, slower card interface chips :) \$\endgroup\$
    – rackandboneman
    Nov 3, 2018 at 20:06

2 Answers 2

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Realistically, the 5D Mark IV in JPEG mode can shoot continuously at its mechanical shutter's maximum burst speed (7 fps) even at UHS-I speeds, so as long as DSLRs use mechanical shutters, UHS-II will only be interesting to people who want to shoot longer bursts at RAW quality. I suspect they assume that this isn't a big enough market.

Sony's A9 sales will tell us whether they're right. If the Sony A9 makes a huge dent in the market, then it's a decent bet that DSLRs designed after the A9 release will have UHS-II and a global shutter. Time will tell.

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Memory card speed is not necessarily the limiting factor for fps (frames per second) or burst counts - the camera must read the sensor data, process them, and generate a file from it. The chips in the camera are highly specialized to do that, but still have limits, and cannot process faster, or get very expensive (that’s a major part of what makes expensive cameras expensive).
As a result, having a significantly faster memory card gives you nothing - the fps is still limited by the camera processing power. So they see no need to hurry and support those medias.

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  • \$\begingroup\$ These technical limits would all affect the burst rate as well, so they cannot explain why a camera would have a high burst rate but not support continuously shooting at that rate even though there are SD cards which would support writing at that rate. \$\endgroup\$
    – Michael Borgwardt
    Oct 9, 2017 at 9:55
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    \$\begingroup\$ @MichaelBorgwardt, I think that argument requires the assumption that buffering only occurs between the CPU and the SD card. Is it known that DSLRs don't also have buffers between the sensor and the CPU? \$\endgroup\$
    – Peter Taylor
    Oct 9, 2017 at 12:28
  • \$\begingroup\$ @PeterTaylor Quite the opposite. It is well known that buffering occurs between the DACs and CPUs as well as between the CPUs and the memory cards. In most instances, though, the write speed of the memory card is still the most restrictive factor, even with faster memory busses such as for UHS II, QXD, or CFast.. \$\endgroup\$
    – Michael C
    Oct 9, 2017 at 15:19
  • \$\begingroup\$ Clearly, the fact that many modern cameras can shoot continuously at burst speeds when emitting JPEG rather than RAW means that CPU/processing speed is not the bottleneck at this point, because cranking out a full-quality JPEG image requires a lot more processing than emitting a RAW file with a mere low-res thumbnail. \$\endgroup\$
    – dgatwood
    Oct 11, 2017 at 0:26

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