6D needs a fast enough SD card for RAW @ 4.5FPS

[EOS6D]

After reading some reviews about issues with (secondary) SD card controller in famous 5D MarkIII camera, I decided to test the one in my new 6D camera.

Speeds tested with same composition and lighting (poor tungsten), same frame settings: exposure 1/200 @ f/1.6 on iso 800, object of shooting was my window mounted room air conditioner (LOL, I know ha ha!):

Since I already spent some time on preparing the information for myself, I thought I'd share it here 🙂

File sizes with approximate write bandwidth at camera's max 4.5FPS (continous shooting mode):
RAW 20M 5472x3648 - file size of 22,814 KB ~ 100.2 MB/s
mRAW 11M 4104x2736 - file size of 16,581 KB ~ 72.9 MB/s
sRAW 5.0M 2736x1824 - file size of 11,228 KB ~ 49.3 MB/s
L high 20M 5472x3648 - file size of 5,303 KB ~ 23.3 MB/s
L medium 20M 5472x3648 - file size of 2,488 KB ~ 10.9 MB/s
M high 8.9M 3648x2432 - file size of 2,463 KB ~ 10.8 MB/s
M medium 8.9M 3648x2432 - file size of 1,090 KB ~ 4.8 MB/s
S1 high 5.0 2736x1824 - file size of 1,470 KB ~ 6.4 MB/s
S1 medium 5.0 2736x1824 - file size of 643 KB ~ 2.8 MB/s
S2 2.5M 1920x1280 - file size of 766 KB ~ 3.4 MB/s
S3 0.3M 720x480 - file size of 155 KB ~ 0.7 MB/s
*approx write bandwidth calculated with formula (FILE_SIZE_KB * 4.5)/1024, results in MB/s rounded up

from observation it seems that file sizes can grow by around extra 50% for JPG (Large high quality) or sRAW at certain composition & light scenarios.

Maximum file sizes I've seen were 27,800 KB for RAW (calling for over 122 MB/s write speed in 4.5FPS continuous shooting mode) and nearly 8 MB for Large JPG in high quality (equivalent of 35.1 MB/s in continuous shooting mode). Former one was no go with Sandisk Extrme SD (bus afte 13 frames), the latter went through no problem for around 30 secs (over 130 frames).

phew ... bottom line is I was able to shoot continuously all kinds of JPG frames infinitely (tested up to 30 secs) with my Sandisk Extreme 45MB/s SD card ... however that's way too slow for any kind of RAW frames - literally after 13-16 frames you will see a "BUSY" message and shutter speed will drop to 0.9FPS until you release the shutter button and let the camera save the buffer to card, then you can repeat.

I was actually thinking of buying the fastest SD card on the market I could find, but gave up after I came back finding only Sandisk SD Extreme Pro cards rated up to 90MB/s write speed, they are probably good maybe up for mRAW, but still not enough for RAW.... hoping the faster SD cards get developed some time in future as I really enjoy pure RAW mode ... and sometimes want to do a series ofshots formorethan 13 frames 😉

Do I need continous shooting mode daily for over 13 frames each time? no, not at all, but someone might and if you do then your only real option is 5DMIII camera (with similar full frame sensor) and a blazing fast CF card that could support infinite shots up to card's capacity.

Good news is that the SD cards are working great (as advertised) in 6D camera! 🙂

hope it helps.

[TCampbell · Accepted solution]

The 6D supports UHS-1 cards.  The UHS-1 standard allows a theoretical bus speed of 312MB/sec.  I say "theoretical" because busses have overhead (usually one "large" file will transfer faster than lots of "small" files) but more importantly... nobody actually makes SD card technology that can transfer data that fast.  So really it's the physical speed of the card that becomes the barrier and not the speed of the bus.

I've seen UHS-1 cards with speeds rated up to about 100MB/sec (that's a rounded value).

The 5D III is different... it's CF slot is fast (CF card slots are generally always fast) but the SD card slot on the 5D III is _not_ a UHS-1 bus slot.  So it doesn't have the fast transfer speed.  If you _need_ that fast transfer speed on a 5D III then you'd want to make sure you've configured it to write to the CF card and buy an appropriately rated CF card that can keep up.

So far, I think only the 6D and the new 70D have UHS-1 SD slots.

If you have a 6D or 70D and you want that speed then you'd want to make sure that your SD cards are UHS-1 cards.  The symbol is a letter "U" with a "1" inside the "U".

[EOS6D]

Thanks TCampbell! I didn't realize the 5dm3 has no UHS-1 support on SD controller hence the reported problems with very slow SD card write speeds even when one used Sandisk Extreme Pro (I think it was topping out around 20 MB/s always ... and also slowing down CF slot whenever SD card was present in slot).

Anyways, glad to hear all is in order in 6D and that one supports true UHS-1 SD bus, I guess we just need to wait for faster cards to hit the market. Knowing the fastest two from Sandisk are Extreme 45MB/s and Extreme Pro 90MB/s, then it seems like the next speed class would be just what 6D needs for continuous RAW shooting mode (up to 130MB/s).

The card used for testing was Sandisk Extreme 45MB/s, UHS-1 rated, class 10.

I will hold off with buying faster card until Sandisk releases the next generation of something that covers 130MB/s bandwidth on SD slot.

[ebiggs1]

"...  make sure you've configured it to write to the CF card and buy an appropriately rated CF card that can keep up."

And these are very expensive!  

[Peter]

The fastest speed 6D can handle is about 50 MB/s. Sandisk Extreme 45MB/s SD card is good enough.

http://www.magiclantern.fm/forum/index.php?topic=6121.0

[ddyourself]

Does this mean there is no point to buy/use the 90MB/s extreme pro cards if the internal rate is 50MB/s?

[hsbn]

Keep in mind that 90Mb/s is the maximum read speed. Write speed is totally different.

[EOS6D]

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@Peter wrote:

The fastest speed 6D can handle is about 50 MB/s. Sandisk Extreme 45MB/s SD card is good enough.

http://www.magiclantern.fm/forum/index.php?topic=6121.0

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Are you certain that 6D controller limit is 50mb/s? or rather that is the limit for video recording (that is what that linked thread is about, lots of buffers and other filters come into play too) only and not the picture shooting mode, e.g. mRAW in continous mode. The controller is UHS-1 still, so I don't see why it would have such low bandwidth limit on all things.

In past I peaked out around the numbers I posted, but that was with older Sandisk Extreme cards (45MB/s), recently I acquired a faster new model of Sandisk Extreme SD card rated at 80MB/s (it's not a pro model, new Pro are rated for 120MB/s). might need to retest some things soon, theoretically it should allowme to shoot continuously mRAW without buffer trouble.

[EOS6D]

well, inconsistent results on our 6D (1.1.3 Canon fw) with 80MB/s card.

I tried continous shooting (all postprocessing and live view options turned off) in 2 output modes:

a) mRAW

avg file size was 17.2MB

was able to shoot 13 frames continously before seeing BUSY message for the first time, that roughly equals to 49.9MB/s bandwidth = (13 pics * 17.2MB size) / 4.5 FPS

b) sRAW

avg file size was 11.9MB

was able to shoot 28 frames continuously before seeing BUSY message for first time, that roughly equals to 74.0MB/s bandwidth = (28 pics * 11.9MB size) / 4.5 FPS

Sounds like there is some internal buffer that might be coming into play with bigger resolutions (mRAW and RAW) which is not the case for sRAW.

The card used for test was Sandisk Extreme SDXC 64GB (80MB/s read & 60MB/s write):

http://www.bhphotovideo.com/c/product/992492-REG/sandisk_sdsdxs_064g_a46_64gb_sdxc_extreme_class.htm...

[Peter]

In playback mode:

http://www.magiclantern.fm/forum/index.php?topic=5471.msg36780#msg36780

Around 41 MB/s