7D: CF Speed 133x vs 200x vs 400x

Started Mar 3, 2011 | Discussions thread
David Burren Regular Member • Posts: 391
Re: David: have you ever tested a double slot (CF & SD) bodies?

jpr2 wrote:

given the really huge performance gap:

  • up to 90 Mb/s with UDMA for CF;

Well, the 1DmkIV seems to max out at around 58 MB/s: http://www.slashgear.com/high-performance-compactflash-benchmarks-on-canon-1d-mark-iv-1577718/

  • vs. just half that (and only 30 Mb/s confirmed) for SD

one wonders how double CF/SD slot cameras are able to cope with
such speed's lack of equilibrium with simultaneous writes??

No I haven't. I've been interested in the speed of cards in my own cameras (currently 7D and 5DmkII). Although I'm a professional photographer so far the 1D-series cameras have not been appropriate for me: the 7D/5DmkII pair is actually better for my uses.

I would assume that basically the camera is at least restricted to the speed of the slowest card. Note that when Rob Galbraith did his tests of the 1DmkIII the SD cards were slightly faster, and with the 1DsIII the CF cards could only pull slightly ahead. So the major disparity will only be with the 1DmkIV at the moment. Of course, if the camera is configured to put RAWs on the CF and JPEGs on the SD it might not be an issue. I don't know anyone who actually has both cards getting the same data: usually the SD card is just an overflow for when the CF fills.
So is it really an important question?

Mind you, next week I'm heading off for another workshop expedition where I'll be amongst folks with an assortment of gear. I suspect my co-instructor will be bringing his 1DmkIV and 1DsIII, and at least one of the participants also has a 1DmkIV. So during the expedition I may get to answer that question. Fastest SD cards I'll have with me (my non-DSLR gear does use SD) are SanDisk Extreme and Transcend class 10. Someone may have a UHC-1 card on the trip, but I doubt it.

However , don't expect to hear from me on this until my return in mid-April. We'll be on a ship for a month (we start off by heading down from South America to Antarctica) and there'll be some time for idle tests when we're at sea. But while I can make short updates via satellite to our blog I won't be able to post here until we get back to the Internet...

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