SD Card slot slow on the 5dmk3?

Sorry if this has been discussed many times before, but I ran accross this article which explaines the CF slot is fast and the SD slot is slow on the 5dmk3.

Has anyone with the mk3 experienced this with SD cards?

http://www.cultofmac.c​om …&utm_campaign=s​cribol.com

Yup - after reading several stories, i tried it for myself. Won't be a problem for me as I only use the SD card as over-run/back-up. When I need maximum speed I use my 1DmkIV.

Ti, who make the DIGIC processors dont offer a DSP with both fast CF and fast SD interfaces. Its this thats the real issue here.

Wiki says that SD 133X is capable of 19.5megaBytes Read, and 19.5megaBytes of writing speed are theoretically possible. So it appears that 20 mega Bytes per second would be the maximum the buffer could be cleared in theory.

This probably isn't apples to apples, but my 5dmk2 has a 13 shot RAW buffer, and clears out in about 3.5 seconds using a 600X CF card. Each image is around 20MB, so that's 260MB/3.5(sec) = 74.X MegaBytes per second of write time. So in relation it doesn't appear that 20MB per second is very stellar. On top of that, the 5D3 has a much larger buffer, so one could potentially be waiting much longer for the buffer to clear.

It puzzles me to no end why Canon would offer dual SD, and yet manufacture a standard (not high speed) SD slot .... Head scratcher***

Rob Galbraith test database has results for 5DIII with fast CF card and with fast SD card.
The fastest CF = 4 * SD, 80 MB/sec vs. 20 MB/sec!

http://www.robgalbrait​h.com …i_page.asp?cid=​6007-12452

SD memory uses serial data transfer, while CF cards use parallel data transfer. SD is the memory industry's attempt to shove slower speed for lower production cost down our collective throats!

Wilt wrote in post #14642552
SD memory uses serial data transfer, while CF cards use parallel data transfer.

This is not always a bad thing. SD's current implementation isnt good but on the whole we have moved to fast serial data transfer over parallel transfer.

IDE-> SATA, Parallel port to USB etc Most data comms is going to serial.

RobDickinson wrote in post #14642589
This is not always a bad thing. SD's current implementation isnt good but on the whole we have moved to fast serial data transfer over parallel transfer.

IDE-> SATA, Parallel port to USB etc Most data comms is going to serial.

But we have, at the same time, also gone to even faster CF card data transfer specification, too!

But there isnt a clear way forward from CF so we have a new standard XQCD or whatever. CF is to some extent a dead end.

It's a huge pain in the a** when I'm shooting weddings. More than a couple of times a night the previews take forever to show up since it's clearing the buffer. It's very irritating to me, especially after dropping $3,500 on the darn thing. Come on, Canon. I record mRAWS to both.

RobDickinson wrote in post #14642675
But there isnt a clear way forward from CF so we have a new standard XQCD or whatever. CF is to some extent a dead end.

A 'dead end' that changed in 2009 to support UltraDMA Mode 7 (167 Mbyte/s), and now CFast which admittedly is based on Serial ATA and as of 2011, SATA supports transfer rates up to 600 Mbyte/s.
But until I see a camera whose serial memory even is as fast as CF, I am not convinced of the death knell of CF.

mritchy wrote in post #14642786
It's a huge pain in the a** when I'm shooting weddings. More than a couple of times a night the previews take forever to show up since it's clearing the buffer. It's very irritating to me, especially after dropping $3,500 on the darn thing. Come on, Canon. I record mRAWS to both.

I thought I read somewhere that shooting mRAW slows the camera data transfer even more?

Very well written article at http://protogtech.com …e-performance-comparison/.

mritchy wrote in post #14642786
It's a huge pain in the a** when I'm shooting weddings. More than a couple of times a night the previews take forever to show up since it's clearing the buffer. It's very irritating to me, especially after dropping $3,500 on the darn thing. Come on, Canon. I record mRAWS to both.

Why don't you shoot RAW to CF and Jpeg to SD?

That is how this seem to have been designed to my mind.

Main images to CF, backup images to SD.

mtimber wrote in post #14643584
Why don't you shoot RAW to CF and Jpeg to SD?

That is how this seem to have been designed to my mind.

Main images to CF, backup images to SD.

The test linked by John from PA indicates why...slower write times than storage of only RAW to CF. The listed times are to write a full buffer to memory card...

"In order of performance, times approximate, measured to highest peak on the last recorded shutter click:

1. 6.9s, Full RAW to CF card only (super fast - no surprise)
   
2. 9.8s, mRAW to CF card, sRAW to SD card. (Interesting how it takes a long time to warm up, then runs pretty quick.)
   
3. 13.8s, Full RAW to CF card, Large/Fine JPEG to SD card.
   
4. 14.4s, Full RAW to CF card, mRAW to SD card.
   
5. 18.1s, Full RAW to SD card only
   
6. 18.6s, Full RAW to both CF and SD cards"

John from PA wrote in post #14643578
Very well written article at http://protogtech.com …e-performance-comparison/.

Article says: "Unfortunately there's a big performance difference between the SD card slot and the CF card slot. If Canon had chosen to support the UHS-I standard, we'd get roughly equal performance."

The Nikon D800 supports UHS-1 yet its raw writing speed to SD is only 60% of the rate to CF.

Also the 1DX supports dual CF cards yet slows down dramatically if writing to both. See 1DX Owner's Manual, page 120.

E.g, 1DX max raw burst size to a single UDMA-7 CF card is 38 frames. If writing separately raw + large jpg to two CF cards, it drops to 17 frames -- despite both cards being UDMA-7.

To me this indicates the 5D3's lack of support for UHS-1 SD cards is less an issue than some think.