Lexar 256mb compact flash reads as 245mb on my A70

Discussion in 'Digital Cameras' started by humphrey stewart, Dec 7, 2003.

  1. Hi,

    I just purchased my first digital camera - canon a70, and a Lexar 12x
    256mb compact flash card. When I pop it in the camera it reads that
    the flash card has 245mb free, not 256mb (nothing's on the cf card).
    Did I get a bad card, or is this normal? 245 * 1.024 is not 256mb so
    what am I missing?


    humphrey stewart, Dec 7, 2003
    1. Advertisements

  2. Neil, your intuition is misleading you here. Flash memory *chips* are used in a variety of different
    applications, but a CompactFlash card operates exactly like an IDE hard drive. It has an IDE
    controller on it, and from the point of view of the computer or camera it's attached to, it is an
    IDE hard drive. The raw storage behind the IDE controller happens to be flash memory chips instead
    of rotating magnetic media, but that's all hidden by the IDE controller.

    Formatting a CompactFlash card means the same thing as formatting any other IDE drive: a FAT or
    FAT32 or whatever file system is written on the drive, and optionally the drive may be checked for
    errors. I can even put a CompactFlash card in my Sharp Zaurus (a Linux PDA) and format it with the
    Linux's 'ext2' filesystem, just like I could format a hard drive.

    Michael Geary, Dec 9, 2003
    1. Advertisements

  3. humphrey stewart

    DHB Guest

    Michael Geary,
    you got it 100% correct! You can buy an adapter to
    slide a CF card into & plug that into your notebooks PC card slot (PCMCIA).
    These adapters cost as little as $8 to $12 USD & when used, your notebook
    see's it, gives it a drive letter & treats it just like an IDE drive
    because for all it knows that's what it is. The reason these adapters are
    so inexpensive is because there is almost no electronics in them, it's not

    Just like IDE hard drives in a PC the onboard IDE controller in a CF
    card has to let the device accessing it "digital camera in this case" know
    when it's ready to accept DATA. This was required because it took time for
    the hard drive heads to move into position to write the data. On an actual
    hard drive the time varied a lot but with Flash Memory the variation is very
    much smaller. Keeping this in mind, have you ever wondered how some
    inexpensive generic cards sometimes out perform the well know brands & why
    some of the same brands fail to read/write reliably in some of the faster

    The answer is that they "cheat" by braking the IDE rules! They program
    the IDE controller on the card to always tell the camera or card reader that
    it's ready to write without it actually checking. This often works because
    by the time the DATA arrives it actually is ready to write. This cheating
    works very well in the cameras because the camera's CPU can't write to the
    card faster than the card can accept the DATA. This is why so few cameras
    benefit much if at all from the very fast cards now available. This
    cheating has all but disappeared now that USB-2, firewire reader/writer &
    much faster camera CPU's have entered the picture because some of them can
    write to a cheating card faster than it is actually ready to write. This
    results in an error that often locks up the camera or card reader/writer.

    The moral here is that it's not always best to pay extra for a faster
    card if it's going to be used on a camera & card reader that are slower than
    the card itself. Also an inexpensive but fast performing CF card is not
    always the safest or most reliable place for your DATA. The beauty of the
    faster cards are generally only seen when you transfer your pictures to your
    PC via a high speed card reader/writer. As for me this is not that
    important since I just do something else while a large card uploads to my
    PC. Fast is nice but reliable is more important to me.

    Not a huge fan of SanDisk but they did create the Compact Flash (CF)
    card which has been an enduring success so I have to give credit where
    credit is due. Great job SanDisk!

    Sorry I got off subject here but it seemed like a good place to clear up
    some related issues that seem to keep coming up in this news group.

    OK, I'll sit back now with flame retardant clothes & endure the

    Respectfully, DHB
    DHB, Dec 9, 2003
  4. In fact, if I'm not mistaken, there are *no* electronics in a CF-PCMCIA adapter. The CompactFlash
    interface is simply a subset of the PCMCIA interface, with 50 pins instead of 68. The CF-PCMCIA
    adapter merely connects the 50 pins of the CompactFlash card to the corresponding 50 pins out of the
    68-pin PCMCIA card.

    (And thanks for the interesting information on CF cards that "cheat" on the IDE specification. That
    is a bit spooky!)

    Michael Geary, Dec 10, 2003
  5. All the CF cards I've bought (various 64MB, 256MB and 1GB cards) have come preformatted with FAT16,
    which is what most cameras use. The cameras I've used do not automatically format a card unless you
    explicitly do it from the menu.
    That makes sense--you're right that a SmartMedia card does not have an onboard IDE controller like a
    CompactFlash card does.

    I have moved CompactFlash cards among various models of Canon, Nikon, and Fuji cameras without
    reformatting them. Each of these brands of camera uses different subdirectories for its photos, so
    the photos from one camera are preserved when using the card in a different brand of camera. Of
    course, you might want to reformat the card in order to reclaim all of the space on it.

    Michael Geary, Dec 10, 2003
  6. humphrey stewart

    DHB Guest

    Michael Geary,
    to answer your question "In fact, if I'm not
    mistaken, there are *no* electronics in a CF-PCMCIA adapter." You may be
    correct in terms of "active" electronics but I suspect there may be a few
    surface mount decoupling capacitors in them, at least in the better quality

    Respectfully, DHB

    corresponding 50 pins out of the
    DHB, Dec 10, 2003
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.