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A7riii write to card speed
  
 
DavidBM
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p.1 #1 · p.1 #1 · A7riii write to card speed


Has anyone done the math on the card write speed for uhs-II cards such that you donít slow down the time it takes to write a full buffer to card?

Iím guessing for stills a 300mb/sec write speed is expensive overkill, but Iíd like to get as fast a buffer clearing as possible...



Nov 10, 2017 at 08:37 AM
tn1krr
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p.1 #2 · p.1 #2 · A7riii write to card speed


If benchmarks made with A9 are used you will need a 300 MB/sec rated card to get bets possible write speed; so to maximize the buffer clearing expect to get very best UHS-II card. If you want to save a bit $$$ many UHS-II cards do pretty well.

http://www.cameramemoryspeed.com/sony-a9/fastest-sd-cards-uhs-i-vs-uhs-ii/

I have 2 pieces of the 2000x UHS-II 64 GB Lexars that are topping the above benchmark waiting for my preordered A7RIII; since we finally get a quick to operate A7 series camera I'm not gonna make any decisions that will slow the camera down; the price diff between the best and decent UHS-II is not that big as I found the Lexars for a decent price.



Nov 10, 2017 at 09:06 AM
LostBoyNZ
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p.1 #3 · p.1 #3 · A7riii write to card speed


This should give a bit of an indication of what to expect, taken from the A9:

https://www.cameramemoryspeed.com/sony-a9/fastest-sd-cards-uhs-i-vs-uhs-ii/

For the A7R III I'd estimate a little under 2 uncompressed raw files could be written to the fastest card a second, or about 3 1/2 a second if they're lossy compressed raws.

That's far from the write speed the cards quote, but still quite a bit faster for the UHS-II cards which are rated for a lower speed. So while 250-300mb/sec write speed is certainly expensive, it's certainly faster too.

Thankfully you can take more shots while the buffer is clearing, but if you ever wanted to wait for the buffer to fully clear for some reason, to save 79 compressed raws should take about 23 seconds.



Nov 10, 2017 at 09:09 AM
tn1krr
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p.1 #4 · p.1 #4 · A7riii write to card speed


LostBoyNZ wrote:
Thankfully you can take more shots while the buffer is clearing, but if you ever wanted to wait for the buffer to fully clear for some reason, to save 79 compressed raws should take about 23 seconds.


I do not think there actually is a 76 compressed RAW image buffer. 76 is the burst length you get if you start shooting and use the fastest possible card that will start writing immediately after 1st shot has been taken. The Sony spec states "up to 76 images continuous shooting" for compressed RAW and to me this must be "rolling" number since otherwize the compressed and uncompressed burst lengths do not match at all with the max burst length being only 28 uncompressed shots. I've estimated about 2 GB buffer size. See below.

8 fps uncompressed shooting generates about 650 MB/sec so one is generating data 500 MB/sec faster than card can write. after about 4 secs a 2 GB buffer would be full. Somewhat matches the promised 28 continuous shots.

10 fps compressed RAW shooting generates about 420 MB/sec, that is about 270 MB/sec faster than best card can write. Filling a 2 GB would take about 7,5 secs. Again quite close to promised 76 compressed RAWs.

Once you have filled a 2 GB buffer completely it should take about 14 or so secs to fully clear it @ 150 MB/sec write speed.



Nov 10, 2017 at 09:36 AM
 

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Stoffer
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p.1 #5 · p.1 #5 · A7riii write to card speed


No matter what, it will be better that this A7rII turtle I have right next to me here,


Nov 10, 2017 at 10:14 AM
LostBoyNZ
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p.1 #6 · p.1 #6 · A7riii write to card speed


tn1krr wrote:
I do not think there actually is a 76 compressed RAW image buffer. 76 is the burst length you get if you start shooting and use the fastest possible card that will start writing immediately after 1st shot has been taken. The Sony spec states "up to 76 images continuous shooting" for compressed RAW and to me this must be "rolling" number since otherwize the compressed and uncompressed burst lengths do not match at all with the max burst length being only 28 uncompressed shots. I've estimated about 2 GB buffer size. See below.

8 fps uncompressed shooting generates about
...Show more

Good points yes, thanks! And that's much better than 23 seconds, thankfully.



Nov 10, 2017 at 08:54 PM
patotts
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p.1 #7 · p.1 #7 · A7riii write to card speed


And what is happening to pricing in this area? Last time I bought a card (March 2017) I got a Lexar Professional 2000x 64GB SDXC UHS-II/U3 for $94 on Amazon, now they are out of business and an equivalent Sony card is $119 and Sandisk is $134?!


Nov 11, 2017 at 12:02 AM







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