Using UHS-II cards in a Sony A7 III

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Celtic imp

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Mar 13, 2021
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Ian Piper
Hi everyone,

I'm new to this forum, but I think I'm posting in the right place. Do set me straight if not. I have a question about use of UHS-II cards in Slot 1 of a Sony A7 III.

On the Quality/image Size 1 menu, I have File Format set to RAW & JPEG. On the Setup 6 >Rec media settings > Recording mode, the options that I think are relevant are:
  • Simult (photo) - this seems to write both RAW and JPEG images to both Slot 1 and Slot 2 simultaneously
  • Sort (RAW/JPEG) - this seems to write a RAW file to Slot 1 and a JPEG file to Slot 2
I lean towards the first option, but could live with the second, depending on the impact on speed of writing to the cards. What is not clear to me at the moment is whether there are any benefits in using a UHS-II card in Slot 1 with either of these options. I read somewhere that using the Simult option makes the write slow down to the speed of the slower card. If I put UHS-II cards in both slots then presumably this also would prevent the Slot 1 card from writing at full speed.
If I use the Sort option, writing RAW to Slot 1 (with a UHS-II card) and JPEG to Slot 2 (with either a UHS-II or UHS-I card), would there still be a speed penalty?

Is there actually any scenario in which a UHS-II card can be used to its full capability?

Apologies if I'm misunderstanding how this works; I'm accustomed to using a Fuji X-T3, which just has UHS-II compatibility in both slots.

Thanks for any guidance.
 

Timothy Mayo

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Hi Ian,

I've tested quite a few cards and different recording setups in my guide here:

If you shoot simultaneous (images) to both slots then you are limited to UHS-I write speeds due to the slower slot 2.

If you shoot sort (raw/jpeg) you are also restricted by slot 2, shooting uncompressed raw in this scenario is a little faster than compressed to clear the buffer, but of course you can't shoot as many shots then.

Really the only scenario where it's beneficial to use UHS-II cards in slot 1 is when you are only shooting to that card. But you can still benefit from the faster read times, so I typically use UHS-II cards in both slots for that reason.

The SanDisk Extreme Pro UHS-II (300/260) was the fastest card that I tested, but not much faster than the Sony SF-M UHS-II (277/150) which is around half the price!

Here are the numbers from the article for these two cards:

SanDisk Extreme Pro UHS-II (300/260)
Uncompressed RAW (49.3MB)
Shots before filling the buffer: 58
Time to clear the buffer: 9.71 seconds

Compressed RAW (25MB)
Shots before filling the buffer: 106
Time to clear the buffer: 13.71 seconds

JPEG Extra Fine (18.3MB)
Shots before filling the buffer: 166
Time to clear the buffer: 53.31 seconds

JPEG Extra Fine + Compressed RAW (18.3MB + 25MB)
Shots before filling the buffer: 79
Time to clear the buffer: 26.73 seconds

Sony SF-M UHS-II (277/150)
Uncompressed RAW (49.3MB)
Shots before filling the buffer: 49
Time to clear the buffer: 12.42 seconds

Compressed RAW (25MB)
Shots before filling the buffer: 106
Time to clear the buffer: 14.39 seconds

JPEG Extra Fine (18.3MB)
Shots before filling the buffer: 167
Time to clear the buffer: 52.70 seconds

JPEG Extra Fine + Compressed RAW (18.3MB + 25MB)
Shots before filling the buffer: 76
Time to clear the buffer: 27.47 seconds

Hope that helps!
 

Reciprocum

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Afonso Santos
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I remember seeing a card test where the reviewer concluded that a7iii's slot 1 write speed was caped itself (by the camera processor ?) to 150mbs no matter what card you used (slower if the card was slower than 150mbs). That was the reason I never bought anything faster than Sony SF-M64T (R277/W150) for my 7M3.
I use sort (uncompressed RAW to slot1, JPEG to slot2) and because JPEGs are smaller than RAWs I also used smaller (half the size in use in slot-1) and slower (about half the write speed in use in slot-1) cards on slot-2 for the backup jpegs (that fortunately I never needed to access in 3 years).
This combination was never slower than when I tested writing only RAWs only to slot-1.

So I started with two sets A/B of (32gb/W150mbs on slot-1, 16gb/W95mbs on slot-2). Whenever a card filled (usually the RAW card always filled first), I swaped both cards of set A with both cards of set B.
About 2 years on prices had dropped and I bought 2x 64gb/W150mbs for slot-1/RAW duty and shifted the 2y old (more probable to fail now) 32gb/W150mbs cards to slot-2/JPEG backup copy duty.

With the A1 I am also pursuing the same strategy: faster CF-A R800/W700 cards for uncompressed RAWs (until CaptureOne supports lossless RAWs) on slot1, slower and smaller R300/W299 cards for backup (downsampled to 21mpx) JPEGs on slot 2 (also Sort recording)

Allow me one advice: whenever possible transfer your images from your camera without removing your card, use the usb-c cable: the card retainer spring/mechanism on my a7iii slot-1 broke and I now manage to keep the card inside only with the external door ...
 
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Reciprocum

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Afonso Santos
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As per the above I now have something to add (and also some change to my advise given then)

I wanted to test real-world transfer speeds/time from a 100% full (1209x uncompressed A1 RAW files) 128GB Sony SF-G128T (UHS-II R300/W299) card to my editing computer (MacMini 2018).

The 2 scenarios I tested were:
1) card inserted into an usb-c SanDisk UHS-II card reader, plugged into one of the PC's thunderbolt/usb-c ports.
2) card remains inside the A1 and an usb-c/usb-c cable is used to connect the A1 to the same PC port as in 1)

Times for full import (into CaptureOne) of the 1209 files/images (128GB):
1) 10' 51" = 651" => 1.85 images/s <=> 183MB/s (yes, well bellow the card - and reader - rated read speed, but CaptureOne was involved...)
2) 54' 32" = 3,272" => 0,37 images/s <=> 36MB/s = 290Mb/s

So I no longer advise to always/exclusively use a cable connection to transfer your files to a PC (just for the purpouse of saving on the mechanical wear of extracting/inserting the card from/into the camera). If a camera has both slots with equal specs than what I do advise is to alternate (I do it monthly) wich of the 2 slots does RAW duty (usually the only card extracted for culling/editing). With A7M3 both cards are not equal hence slot-1 was the one that always had RAW duty (sort RAW-1 JPEG-2) and it was the one who's spring card retainer failed on me.
 

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