# CompactFlash vs SDXC (Effectively 5D3 vs 6D)



## Botts (Nov 26, 2012)

Hello,

I haven't used a SDXC based camera other than a Kodak PlaySport in years.

Is there a major detriment to using SDXC instead of CompactFlash?

I am looking at buying a 6D, but the SDXC cards are worrying me. Is this something to be concerned about?

I greatly appreciate your comments.


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## Chosenbydestiny (Nov 26, 2012)

With CF it's all about durability and compatibility with pro cameras, speed should be about the same with both. Advantage of sd cards is compatibility in everyday devices like integrated slots in computers, tablets, etc.


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## Drizzt321 (Nov 26, 2012)

Also, SD/SDHC/SDXC is considered by some to be more reliable since it doesn't have any pins that can be bent, which is true. However they tend to just feel a bit flimsier to me than CF.


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## raptor3x (Nov 26, 2012)

Drizzt321 said:


> Also, SD/SDHC/SDXC is considered by some to be more reliable since it doesn't have any pins that can be bent, which is true. However they tend to just feel a bit flimsier to me than CF.



Samsung makes some very nice metal SD cards that feel almost as sturdy as CF cards.


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## Botts (Nov 26, 2012)

Thanks for the feedback so far.

Speed has been my biggest concern. I've been more worried about pin issues damaging the camera than the card, so that is moot for me.

It surprises me that the costs seem similar when SD has to be so much more minimized than CF.


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## Drizzt321 (Nov 27, 2012)

Botts said:


> Thanks for the feedback so far.
> 
> Speed has been my biggest concern. I've been more worried about pin issues damaging the camera than the card, so that is moot for me.
> 
> It surprises me that the costs seem similar when SD has to be so much more minimized than CF.



In terms of pure write speed, the Lexar 1000x UDMA7 cards are the fastest cards out there in a UDMA7 camera, barring the XQD which right now only the Nikon D4 supports. Most SDXC UHS-1 cards will still give great performance, in a camera with a UHS-1 slot, but they still won't perform quite as high as the top performing CF card.

Personally, I can't wait for the XQD, and I hope the next Canon and Nikon's support them, even if it does mean needing to buy all new cards for the camera. Of course, for me that's 3-5 years off most likely, so by then there should be a good number of cards and readers out there.


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## RustyTheGeek (Nov 27, 2012)

I've always preferred CF for many reasons, not the least of which is speed and physical size. The CF cards I have tend to be faster than the SD counterparts rated for the same speed. Without a lot of careful testing it's hard to quantify this but I've read detailed accounts on the web of folks who have tested them heavily and the CF cards always outperformed the SD cards. I suspect this is why the faster cameras like the 7D and 1DX still use CF as a primary format. Also, all the pins on a CF card are for better grounding. This equates to better more stable data transfer. And finally, CF cards are just a lot easier to manage in the field. At least to me they are.

Anyway, that is my OPINION, please let's not start a big war on formats and specs. It boils down to personal preference because BOTH are so close that it really doesn't matter. And UHS-1 SD cards are very fast. Much better than the SDHC cards that I tend to look down on.

It's ridiculous that Canon didn't put a UHS-1 slot in the 5D3. If you get a 5D3, make sure to read this about how slow the 5D3 writes will be if you use the SD card slot! http://jeffcable.blogspot.com/2012/06/why-you-should-not-put-sd-card-in-your.html

Let us know how it goes!


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## Botts (Nov 28, 2012)

Wow, I didn't know about that with the 5D3's SD slot.


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## Mt Spokane Photography (Nov 28, 2012)

I use a SDXC card in my 5D MK III (its not UHS-1). I do not try to shoot the high FPS rate, so its no issue. If I were shooting high FPS, I'd merely stop recording to both cards.

If you think about it, when writing to both cards, the speed of the slowest card will limit the writing speed. Thats almost always the SD card.

Unfortunately, the design of the 5D MK III was apparently frozen before SDXC UHS-1 cards arrived. Its unfortunate, but true.


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## Drizzt321 (Nov 28, 2012)

Mt Spokane Photography said:


> I use a SDXC card in my 5D MK III (its not UHS-1). I do not try to shoot the high FPS rate, so its no issue. If I were shooting high FPS, I'd merely stop recording to both cards.
> 
> If you think about it, when writing to both cards, the speed of the slowest card will limit the writing speed. Thats almost always the SD card.
> 
> Unfortunately, the design of the 5D MK III was apparently frozen before SDXC UHS-1 cards arrived. Its unfortunate, but true.



True, but looking out even 1-2 years and it should have been pretty obvious that UHS-1 cards were coming, and quickly. Besides, an SDXC UHS-1 slot would work just fine with the slower speeds. Personally, I suspect that the DIGIC 5+ only has 1 super-high speed storage interface, so the SD slot has to hang off of a slower bus. The 1D-X doesn't have this problem since it has 2 DIGIC 5+ which gives it the 2 super-high speed interfaces, 1 per chip.


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## Botts (Nov 28, 2012)

I'm hijacking my own thread, but it seems that this would be an easy fix for some users from Canon.

Have the camera record to the CF card at max speed, and then copy from the CF card to the SD card when there is downtime. If the CF card could read/write at maximum speed at the same time, then this would be seamless.
I don't know if the DIGIC 5+ just refers to the processor or the entire logic board, but you'd imagine that Canon could designed it so that the DIGIC 5+ dump the data to a second system that handles the CF/SD I/O.


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## Drizzt321 (Nov 28, 2012)

Botts said:


> I'm hijacking my own thread, but it seems that this would be an easy fix for some users from Canon.
> 
> Have the camera record to the CF card at max speed, and then copy from the CF card to the SD card when there is downtime. If the CF card could read/write at maximum speed at the same time, then this would be seamless.
> I don't know if the DIGIC 5+ just refers to the processor or the entire logic board, but you'd imagine that Canon could designed it so that the DIGIC 5+ dump the data to a second system that handles the CF/SD I/O.



Not sure, but the DIGIC 5+ probably uses a DMA (built into pretty much all modern, reasonably high performing processors these days) controller to transfer from RAM to the memory card(s). 

In terms of having it automatically copy from CF to SD, the big challenge I think is that you never know when someone is going to start doing a big burst of images which need flushing to the CF card. Personally I'd never use that functionality, it could potentially be error prone where the camera thinks it's successfully copied something from the CF to the SD card, but then it's only partially there, or not at all and deletes it from the CF card. Oops. I'd rather the camera only ever write to the memory card, except when I tell it to delete/format.


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## Botts (Nov 28, 2012)

I appreciate the concern with data integrity, but it could be possible for the camera to verify the copies with an MD5 or SHA-1 process. I think you would also design it to maintain the CF copy as a master.

That aside, thank you everyone for your comments on the benefits and cons of CF vs SD.


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## jp121 (Dec 7, 2012)

The Canon 5DM3 write speed in Rob Galbraith's CF/SD/XQD Performance database. Unfortunately there is no information for the 6D.

http://www.robgalbraith.com/bins/camera_wb_multi_page.asp?cid=6007-12452


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## Botts (Dec 10, 2012)

My concerns about speed were generally unfounded.

I just tested my memory cards for speed:

*Card Type**Card Write Speed**Card Read Speed*SD - SanDisk 16GB Extreme Pro UHS-1 95MBps70.5MBps87.5MBpsSD - Transcend UHS-1 32GB35.0MBps84.5MBpsCF - Transcend 16GB 600x26.9MBps78.7MBps

The SD UHS-1 cards truly surprised me! I also learned that the SDXC readers in Retina MacBook Pro's are direct to the logic board and transfer at 2.5GT/s, which is well into the GB/s range. The old MacBook Pro's used to have their SDXC readers attached to the USB 2.0 bus, so they were limited to a theoretical maximum of 60MBps.

I'm quite happy with new SDHC cards!


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## Drizzt321 (Dec 10, 2012)

Botts said:


> My concerns about speed were generally unfounded.
> 
> I just tested my memory cards for speed:
> 
> ...



So I'm guessing you got the 6D? Or are these speeds with your MacBook Pro? How did you come up with the CF card speeds? With my 32GB Transcend I've gotten >100MB/sec sustained via the Lexar CF/SD Pro USB3 reader to my mSATA SSD on my laptop (after recent Lexar firmware update). Sure that's reads, but writes are supposed to be a good bit higher. Or was your OP about whether the SDXC/UHS-1 cards would be significantly slower than modern CF cards?


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## RLPhoto (Dec 10, 2012)

CF > SD


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## Botts (Dec 10, 2012)

Drizzt321 said:


> Botts said:
> 
> 
> > My concerns about speed were generally unfounded.
> ...



The test was with my MacBook Pro, I did get a 6D too.

I used a Delkin USB 3.0 reader for the CF cards. And I reran the SD test with the Delkin and got numbers that were statistically identical.

I used BlackMagic's Disk Speed Test app for Mac to test speeds.

I had assumed that the UHS-1's wouldn't compete with the modern CF cards.


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## Mt Spokane Photography (Dec 10, 2012)

Botts said:


> My concerns about speed were generally unfounded.
> 
> I just tested my memory cards for speed:
> 
> ...


Was the test done in a Mac or a camera? There is no way a SD card will operate that fast in a 5D MK III, maybe a 6D. 
Test methods can make a huge difference in file transfer speed. The fastest speed is usually by transfering very large files, 1GB for example. The file format of the card can allow higher speeds as well, because compression rates vary.
Transfering a large number of jpeg files will be slower.


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## Botts (Dec 10, 2012)

The cards were formatted by a 7D, and 6D respectively.

The BlackMagic test as far as I'm aware uses raw video files to test speeds. So it should be close to what one would see using a DSLR for video.

The BlackMagic test I was using was using 1TB files.


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## fonts (Apr 3, 2013)

RLPhoto said:


> CF > SD



C'mon. Stop supporting CF tech. SD is catching up in a more reliable and convenient package and on top of that its less expensive. At the current speeds they both are way passed practical speeds from what current cameras offer. Let CF die...


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## RLPhoto (Apr 3, 2013)

fonts said:


> RLPhoto said:
> 
> 
> > CF > SD
> ...



My d30 is CF only and I need to support CF until another format like XQD is adopted on canon. SD really sucks on the mk3.


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## fonts (Apr 3, 2013)

RLPhoto said:


> fonts said:
> 
> 
> > RLPhoto said:
> ...



Haha I see : I just want camera manufacturers to stop CF slots. It'll save them space for other electronics and it'll make our end a lot easier when all cameras have the same standard and computers can easily take SD. ;D


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## Drizzt321 (Apr 3, 2013)

fonts said:


> RLPhoto said:
> 
> 
> > fonts said:
> ...



Actually, I only see the SD physical interface as being more reliable than CF. I personally think the CF cards themselves (at least electronics inside) tend to be built in such a way as to be more reliable. An SD card has significantly smaller amount of space for NAND dies and controller, while the CF card has more room for more dies and potentially better controller which can do a better job of cleaning up space that's not being used to keep write speeds high.

Now, I very much can't wait to see XQD being widely adopted. Must faster theoretical throughput via PCIe, plus I think with a simple adapter I can stick it into my laptop's ExpressCard slot and read it at extremely high rates. Plus slightly smaller size than CF.


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