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Thread: SD and CF speeds

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    Equilibrium8's Avatar
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    SD and CF speeds

    Hi

    I'm wondering about SD and CF cards. The general consensus is that SD cards faster than 6X are pointless because camera speeds are not any faster. But then some say CF cards are better because they are faster. This is illogical to me.

    I'm assuming this is not actually a speed issue, but how the cards handle the data. Can anybody explain it?

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    Re: SD and CF speeds

    Hi Kenny,

    SD cards are now rated in "classes" rather than the old "x" system - so a Class 6 (if that's what you meant) is 6MB per second - so at that rate it would take 4 seconds to transfer just 1 photo from my camera's buffer - and the camera can do 5 per second - so it would only be capable of 5% of what the camera is capable of (and mine is an old camera by modern standards) (1Ds3).

    Some SD cards are now up to at least 95MB per second though, but some CF cards are now up to 100MB per second -- so they're pretty close, but a class 6 would be hopelessly inadequate for any kind of burst shooting.

    So "Myth Busted" IMHO

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    Re: SD and CF speeds

    Quote Originally Posted by Colin Southern View Post
    Hi Kenny,

    SD cards are now rated in "classes" rather than the old "x" system - so a Class 6 (if that's what you meant) is 6MB per second - so at that rate it would take 4 seconds to transfer just 1 photo from my camera's buffer - and the camera can do 5 per second - so it would only be capable of 5% of what the camera is capable of (and mine is an old camera by modern standards) (1Ds3).

    Some SD cards are now up to at least 95MB per second though, but some CF cards are now up to 100MB per second -- so they're pretty close, but a class 6 would be hopelessly inadequate for any kind of burst shooting.

    So "Myth Busted" IMHO
    Thanks Colin.

    So then, the "Class 6 is as fast as a camera can match" is BS? I just added some Class 10 cards to mine and nice to know that they are actually faster (haven't used them yet, and only bought them because the TDKs were on sale)

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    Re: SD and CF speeds

    Quote Originally Posted by Equilibrium8 View Post
    Thanks Colin.

    So then, the "Class 6 is as fast as a camera can match" is BS? I just added some Class 10 cards to mine and nice to know that they are actually faster (haven't used them yet, and only bought them because the TDKs were on sale)
    In a word, yes. If you've only shooting 1 frame every 5 seconds then they'll be fine, but anything faster and you'll eventually fill the buffer completely (assuming a 18 - 21MP type camera). My 1Ds3 takes CF and SD cards, and I used to have it set to automatically switch from one to the other if the first gets full ... when that happens it slows down dramatically with a Class 6 card.

    Class 10 was a bit different -- for a long time class 10 wasn't explicitly defined, so rather than a class 10 being a 10MB/s in reality it meant "anything faster than a class 6" - and so there was a HUGE variation between class 10 cards. Not sure what the current state of the market is though -- had a feeling that class 10 was eventually officially defined, but I don't follow it too closely.

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    Equilibrium8's Avatar
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    Re: SD and CF speeds

    Thanks Colin. Filling the buffer isn't a problem for me, as most of the time my shooting speed is entirely dependent on the flash's recycle time.

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    Re: SD and CF speeds

    Also, if you are using your camera for any type of video, the class 10 will help, and some manufacturers state the camera needs a class 10 for the video.

    For CF cards I see the difference in the uploading to the computer.

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    Re: SD and CF speeds

    Quote Originally Posted by PBelarge View Post
    Also, if you are using your camera for any type of video, the class 10 will help, and some manufacturers state the camera needs a class 10 for the video.

    For CF cards I see the difference in the uploading to the computer.
    Thanks Pierre. Video is not an issue at the moment, but I'll be upgrading to 60D soon, so that's useful to know.

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    Re: SD and CF speeds

    I never noticed any great difference in CF card speeds (and I have a great variety of speeds) until I began shooting with my 7D. Perhaps the noticible difference is because the 7D produces larger files or perhaps because the 7D is UDMA capable while my 40D is not. However, I notice a great difference in performance between my 300x and 400x CF cards and my slower cards when shooting with the 7D. I do not, however, notice a great performance difference between the 300x and 400x cards. The UDMA card, even though it did not peform more efficiently in my 40D did download from the card to the computer faster if I used a UDMA Capable reader. This has been important when I was in a hurry to download such as on my trip to China when I downloaded every night aftr returning to my hotel room fairly late.

    OTOH my new Panasonic TM900 camcorder directions state that SDHC of a minimum Class 4 memory crds should be used. The camera has an internal 32GB memory and I have an additional 16GB Class 10 SDHC card.

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    Re: SD and CF speeds

    My new camera now only shoots SD (so many CF cards and what to do?).
    Anyway, I bought a class 4 recently and a class 10 today. Put the camera on continuous, fastest (12fps).
    Pressed trigger until camera stops (13 frames).
    Time to LCD screen coming back: -
    Class 4 took 18 seconds
    Class 10 took 16 seconds.
    Old no name card took around 30s.

    I can't compare CF and SD as camera only takes SD.

    Graham

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    Re: SD and CF speeds

    Quote Originally Posted by GrahamH View Post
    My new camera now only shoots SD (so many CF cards and what to do?).
    Anyway, I bought a class 4 recently and a class 10 today. Put the camera on continuous, fastest (12fps).
    Pressed trigger until camera stops (13 frames).
    Time to LCD screen coming back: -
    Class 4 took 18 seconds
    Class 10 took 16 seconds.
    Old no name card took around 30s.

    I can't compare CF and SD as camera only takes SD.

    Graham
    Very interesting Graham!

    What camera is it, and how big are the photos?

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    Re: SD and CF speeds

    Quote Originally Posted by Equilibrium8 View Post
    Thanks Pierre. Video is not an issue at the moment, but I'll be upgrading to 60D soon, so that's useful to know.
    Kenny
    You are welcome.

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    Re: SD and CF speeds

    Quote Originally Posted by Colin Southern View Post
    Very interesting Graham!

    What camera is it, and how big are the photos?
    I'm sure the camera will have a great impact on the value of faster SD cards. The camera has to move some data around too, and in the end the data bus speed that the camera uses to communicate with the SD card is the limiting factor. I imagine there are a 100+ different speeds of data buses used in DSLR's over the years

  13. #13
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    Re: SD and CF speeds

    Quote Originally Posted by GrahamH View Post
    My new camera now only shoots SD (so many CF cards and what to do?).
    Anyway, I bought a class 4 recently and a class 10 today. Put the camera on continuous, fastest (12fps).
    Pressed trigger until camera stops (13 frames).
    Time to LCD screen coming back: -
    Class 4 took 18 seconds
    Class 10 took 16 seconds.
    Old no name card took around 30s.

    I can't compare CF and SD as camera only takes SD.

    Graham
    Thanks, that is interesting. I should check that out with my current cards.

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