An Overlooked Benefit of XQD in the Nikon Z System

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Walter Rowe
There is one aspect of Nikon’s choice of XQD over SD that I feel worthy of more attention. Nikon explicitly states that CFexpress will be supported with a firmware upgrade. This gets little attention in the press. I think this is because most authors do not fully realize what this upgrade will do for owners of cameras that support XQD. CFexpress has the same form factor as XQD, but the CFexpress technology has far greater potential.

Much attention is given by the nay-sayers to the small buffer size and lack of dual card slots in the Nikon Z system. The narrative is that the Z system will not cater to sports and wedding photographers. When you look more closely at the specifications for CFexpress you must concede that Nikon, in fact, made a very intelligent decision when they chose XQD over SD.

CFexpress has the capability of 8GB per second transfer rate via eight 1GB channels. This could make in-camera 6K and 8K video and 60+ fps still image capture a very achievable possibility. Read this article for a detailed comparison of SD, XQD and CFexpress.

EXCLUSIVE REVIEW: ProGrade Digital’s new 1400 MB/s CFexpress card is memory’s brave new world

“With 1044.5 MB/s write and 1437.9 MB/s read speeds, this new technology is going to completely change the memory industry. With so much capability in such a small card, not to mention the massive capacity of 1 TB (ProGrade said that when they release this card later this year, they will also offer lower capacities of 256GB and 512GB), the options for camera companies explodes beyond current limits. 6K video internal? 8K video internal? Both of those in RAW? More? What about 50 or 60 still photos a second for sports? 80? 100? The numbers add up if you look at what can be done with current XQD or even SD cards. The ramifications of this technology can't even be properly quantified at present, there is so much that is possible.”​

Even SD UHS-3 over PCIe 3.0 peaks at 968MB per second and thus can never achieve this transfer rate of CF Express. With a PCIe 2.0 bus, CF Express delivers 1GB per second write speed and 1.4GB per second read speed. This equates to 20 frames per second for 50MB full-frame sensors. For smaller sensors, the frame rate increases. As the technology develops and PCIe 3.0 bus is delivered in cameras, CF Express can achieve its maximum of 8GB per second.

At some point the bus speed and transfer rate will become so fast that we could see cameras with little or no internal buffer. The CFexpress Wikipedia page has a nice comparison chart. As camera manufacturers produce cameras with full support for this technology, the need for large buffers inside the camera will diminish. As processing power in-camera increases and transfer rates of CF Express become available, we could get to 100 frames per second still image capture rate. This technology has significant potential. It would enable in-camera 8K video and cinematic recording, and still image capture in excess of 160 frames per second for 50MB sensors.

What wedding or sports photographer could say they are being left out at 20 frames per second?

Sony video cameras, Nikon DSLRs, the Nikon Z mirrorless cameras, and PhaseOne's new IQ4 150MB digital back all support XQD. A firmware upgrade will enable them to support CF Express with 1GB per second write speed and 1.4GB per second read speed and a card size of 1 terabyte. The real question journalists should be asking is when will their camera maker support XQD or CF Express?
 
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