A while back I noted that the Fuji X-T1 is one of the few cameras that can use a high-speed UHS-II card. That article is here if you want to review it.
After it appeared, Ctein wrote to say:
I'm not so sure those UHS-II cards are a wise investment. I'd be very surprised if the Fuji can max out a 90 MB/sec. card. That would correspond to a sustained throughput of about six RAW images per second. Can it really process anywhere near that fast? I'm not saying the 250 MB/sec. card won't gain you something, but it's a lot like putting a really fast hard drive in a relatively slow computer. There's an incremental improvement but it's modest. Definitely, cards under 20–30 MB/sec are real bottleneck. But above that?
The way to find out is to do a time to comparison. Put in a 90 GB/sec card, set your camera to continuous burst, and mash down the shutter release. When it indicates the buffer is full (by refusing to make any more photographs or slowing way down), take your finger off of the release and time how long it takes to clear the buffer. Also, make note of how many photographs you are able to make before the buffer was full. Now repeat this with your 250 MB/sec card. How much of an improvement in buffer clearing time was there (and,if you could capture any more photographs in burst before running out of buffer)? Was the improvement in performance enough to be worth spending 4–10 times as much for the cards?
I performed the test he suggested using three cards: A 30 MB/sec. SanDisk Ultra, a 94 MB/sec. Sony, and a 280 MB/sec. SanDisk ExtremePro UHS-II card
The slow Ultra did indeed prove a bottleneck: shooting large JPEGs plus RAW in continuous high (CH) mode (about 8 frames per second), the camera made 20 exposures before slowing to about one exposure every three or four seconds, and it took 1 min. 35 sec. to clear the buffer.
Moving up to the Sony, the camera made 22 exposures at high speed, then took 23 seconds to clear. The shooting rate with the buffer full improved to about one frame per second.
UHS-II card (right) is identifiable by its additional contacts
With the new ExtremePro UHS-II card, the camera took 24 exposures at high speed, and the buffer was cleared in 11 seconds. Moreover, the "buffer full" shooting rate only slowed to about 2 frames per second. I kept up the "buffer full" 2-FPS rate going for 1 min./120 shots, at which point the buffer required 9 seconds to clear.
So it appears that for me, under these shooting conditions, with these cards, the UHS-II card in the Fuji X-T1 records only a few more frames at the Continuous High shooting rate, but then clears about twice as fast as the 94 MB/s card, and also shoots twice as fast after the buffer's full.
You might have different UHS-I cards, and you might be interested in some other performance parameter, such as maximum number of frames in continuous low (CL) mode (which I didn't test). Don't extrapolate from my results to other conditions, and don't make the conceptual mistake of thinking one product is "better" unless it's actually better at the parameter you care about. For instance, if the number of frames captured at high speed were what I was interested in, it's pretty obvious that the increased performance of the ExtremePro card is marginal in that parameter. But if the FPS after the buffer is full is what you care about, then the UHS-II card is worthwhile.
Note also that only a few cameras can utilize UHS-II cards at the present time; the Fuji X-T1 is one of them. The Panasonic GH4 is the only other one I know about. There will doubtless be more in the future.
As Ctein notes, the real decision is whether the tested improvements in performance are worth the increase in cost. And that's up to you to decide.
Mike
(Thanks to Ctein)
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Featured Comments from:
Peter Foiles: "You don't address another benefit of fast cards and that is how fast you get your images off the card and on to your computer. You need a USB-3.0-based UHS-II card reader to take full advantage."
Mike replies: As Peter says, you need a UHS-II card reader to see the improved speed of the cards while downloading. I didn't test downloading because I use the card reader on my MacBook Air.
