CF card capacity - different to usual

Discussion in 'Digital Photography' started by John Fryatt, Jun 28, 2006.

  1. John Fryatt

    John Fryatt Guest

    Hi,

    I just got a new CF card, 1Gb. When formatted in my camera it shows up
    as 980Mb. The thing is, my other 1Gb CF cards all format to 988Mb. Why
    should this one be 8Mb smaller? Assuming it's a bad block or some such
    thing, would it remain stable that way, or is the card likely to
    deteriorate?

    (Cards are all Sandisk Ultra II. Camera is Canon EOS 5D)

    Thanks for any advice,

    John
     
    John Fryatt, Jun 28, 2006
    #1
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  2. John Fryatt wrote:
    > Hi,
    >
    > I just got a new CF card, 1Gb. When formatted in my camera it shows up
    > as 980Mb. The thing is, my other 1Gb CF cards all format to 988Mb. Why
    > should this one be 8Mb smaller? Assuming it's a bad block or some such
    > thing, would it remain stable that way, or is the card likely to
    > deteriorate?
    >
    > (Cards are all Sandisk Ultra II. Camera is Canon EOS 5D)


    I have no definitive answer, just another data point.

    I have 3 Sandisk UltraIIs, one 2GB and two 1GB. I got all three
    from "reputable" dealers, so I don't THINK that any of them are
    fake.

    One of the 1GB cards has the serial number along the "side" edge.
    The other 1GB card and the 2GB card both have the serial number
    along the "bottom" edge.

    The cards with the "bottom" serial indicate they will hold
    111 and 222 RAW pictures from my Canon 20D. The 1G card with
    the "side" number only indicates 109.

    After formatting in the camera:
    2G (bottom) card shows 65,536 used, 2,039,480,320 free
    1G (bottom) card shows 32,768 used, 1,011,367,936 free
    1G (side) card shows 32,768 used, 1,011,367,936 free

    I can't figure out how to show if there are any "bad sectors"
    on a CF card, and I've been using both of the 1G cards for
    more than a year with no problems. But SOMETHING must be
    indicating to the camera that there's less available space
    on the 1G (side) card...
     
    Philip Bailey, Jun 28, 2006
    #2
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  3. John Fryatt

    John Fryatt Guest

    Philip Bailey wrote:
    > John Fryatt wrote:
    >> Hi,
    >>
    >> I just got a new CF card, 1Gb. When formatted in my camera it shows up
    >> as 980Mb. The thing is, my other 1Gb CF cards all format to 988Mb. Why
    >> should this one be 8Mb smaller? Assuming it's a bad block or some such
    >> thing, would it remain stable that way, or is the card likely to
    >> deteriorate?
    >>
    >> (Cards are all Sandisk Ultra II. Camera is Canon EOS 5D)

    >
    > I have no definitive answer, just another data point.
    >
    > I have 3 Sandisk UltraIIs, one 2GB and two 1GB. I got all three
    > from "reputable" dealers, so I don't THINK that any of them are
    > fake.
    >
    > One of the 1GB cards has the serial number along the "side" edge.
    > The other 1GB card and the 2GB card both have the serial number
    > along the "bottom" edge.
    >
    > The cards with the "bottom" serial indicate they will hold
    > 111 and 222 RAW pictures from my Canon 20D. The 1G card with
    > the "side" number only indicates 109.
    >
    > After formatting in the camera:
    > 2G (bottom) card shows 65,536 used, 2,039,480,320 free
    > 1G (bottom) card shows 32,768 used, 1,011,367,936 free
    > 1G (side) card shows 32,768 used, 1,011,367,936 free
    >
    > I can't figure out how to show if there are any "bad sectors"
    > on a CF card, and I've been using both of the 1G cards for
    > more than a year with no problems. But SOMETHING must be
    > indicating to the camera that there's less available space
    > on the 1G (side) card...


    Hmmm... strange things, these CF cards.

    Some more data..

    My cards show (when formatted in the camera)
    32,768 used 1,036,042,240 free (x4)
    32,768 used 1,027,827,472 free (the one I am asking about)

    So, that's slightly more confusing. Why should my 1Gb cards format to a
    different size to yours?
    Mine five cards vary slightly in appearance, which I put down to be
    different ages and Sandisk changing their labels, but maybe some are
    fakes? I hadn't really considered this for small value items like this,
    but I guess they could be.
    Sandisk tech. support aren't a lot of help either. Don't seem that
    knowledgeable about their own product, to be honest.

    I guerss, at the end of the day, 8Mb =/- on a 1Gb size card doesn't
    really matter, and I got it pretty cheap, but I'd just like to know
    what's going on. Also I'd like to be sure the card won't suddenly lose
    some more space, with my pictures in it!
    Sadly, as with a lot of IT things, getting the real facts is difficult.

    John
     
    John Fryatt, Jun 29, 2006
    #3
  4. John Fryatt wrote:

    > Hmmm... strange things, these CF cards.


    And, computers in general. :)

    > So, that's slightly more confusing. Why should my 1Gb cards format to a
    > different size to yours?


    There's another question for the gallery... but, I *am* using
    a 20D. It's possible there was a "format change" between the
    20 and the 5...

    > Mine five cards vary slightly in appearance, which I put down to be
    > different ages and Sandisk changing their labels, but maybe some are
    > fakes? I hadn't really considered this for small value items like this,
    > but I guess they could be.


    I really don't know. I've heard about people getting "ripped off"
    on ebay, but I thought, in general, the tip off was the card SPEED,
    not the capacity.

    > Sandisk tech. support aren't a lot of help either. Don't seem that
    > knowledgeable about their own product, to be honest.


    That confirms what anecdotal evidence I've heard, too...

    > I guerss, at the end of the day, 8Mb =/- on a 1Gb size card doesn't
    > really matter, and I got it pretty cheap, but I'd just like to know
    > what's going on. Also I'd like to be sure the card won't suddenly lose
    > some more space, with my pictures in it!


    As I said, even my one "weird" card has been ultimately dependable.
    I can't say if it's a "bad sector" deal or what. If I was a "pro"?
    I'd probably chuck it and get another. As it is, the "weird" card is
    now my "spare".

    > Sadly, as with a lot of IT things, getting the real facts is difficult.


    Agreed. Hey, if you hear anything else, please post it here? I've
    checked with my regular (non-photo) IT guy, and he can't think of
    any "easy" answers. I'll be watching the thread, and hoping that
    someone comes up with SOME kind of definitive answer before I leave
    for the Grand Canyon in 2 weeks!

    Good luck!
     
    Philip Bailey, Jun 29, 2006
    #4
  5. John Fryatt

    ASAAR Guest

    On Thu, 29 Jun 2006 00:33:37 GMT, John Fryatt wrote:

    > So, that's slightly more confusing. Why should my 1Gb cards format to a
    > different size to yours?
    > Mine five cards vary slightly in appearance, which I put down to be
    > different ages and Sandisk changing their labels, but maybe some are
    > fakes? I hadn't really considered this for small value items like this,
    > but I guess they could be.


    Flash cards are designed to appear as if they're hard disk drives.
    That means that they should indicate a fictitious number of
    cylinders, sectors per track and platters. For instance, a ten year
    old WD Caviar 1.6GB hard drive has on its label:

    > Drive parameters: 3148 cyl. • 16 heads • 63 spt • 1624.6 MB


    With a sector size of 512 bytes, that works out to 1,624,670,208
    "marketing" bytes. Dividing by 1024 * 1024 results in 1,549.4 MB.
    Another hard drive manufacturer might have made a hard drive with
    3252 cylinders, 15 heads and 64 sectors per track (and the same
    sector size) and gotten a 1,601,372,160 byte drive (1,527.2 MB).
    Both probably would have been marketed as 1.6 GB drives.

    Many flash memory cards have more than the reported amount of
    memory. Some of it is used to remap bad sectors (when they occur)
    so that the drives continue to function without appearing to have
    lost any capacity, at least while there are spare sectors remaining.
    I don't know if any of your camera's memory cards do this, though.
    It depends on how the cards were designed. Whether a given card has
    a slightly smaller or greater reported capacity than one from
    another manufacturer, or a different model from the same
    manufacturer, it won't be a good predictor of the card's quality.
     
    ASAAR, Jun 29, 2006
    #5
  6. John Fryatt wrote:
    > Philip Bailey wrote:
    > > John Fryatt wrote:
    > >> Hi,
    > >>
    > >> I just got a new CF card, 1Gb. When formatted in my camera it shows up
    > >> as 980Mb. The thing is, my other 1Gb CF cards all format to 988Mb. Why
    > >> should this one be 8Mb smaller?> Some more data..

    >
    > My cards show (when formatted in the camera)
    > 32,768 used 1,036,042,240 free (x4)
    > 32,768 used 1,027,827,472 free (the one I am asking about)
    >
    > So, that's slightly more confusing. Why should my 1Gb cards format to a
    > different size to yours?


    It can depend on what the card tells the camera.

    More peculiar is that the odd one you are asking about is clearly not a
    multiple of any valid blocksize for a FAT formatted disk (is there a
    typo???)

    1,036,042,240 = 16 x 1024 x 63235
    1,027,827,472 = 16 x 64239217 (most odd)

    I'd expect a cluster size of at least 1024.

    Regards,
    Martin Brown
     
    |||newspam|||@nezumi.demon.co.uk, Jun 29, 2006
    #6
  7. John Fryatt

    John Fryatt Guest

    |||newspam|||@nezumi.demon.co.uk wrote:
    > John Fryatt wrote:
    >> Philip Bailey wrote:
    >>> John Fryatt wrote:
    >>>> Hi,
    >>>>
    >>>> I just got a new CF card, 1Gb. When formatted in my camera it shows up
    >>>> as 980Mb. The thing is, my other 1Gb CF cards all format to 988Mb. Why
    >>>> should this one be 8Mb smaller?> Some more data..

    >> My cards show (when formatted in the camera)
    >> 32,768 used 1,036,042,240 free (x4)
    >> 32,768 used 1,027,827,472 free (the one I am asking about)
    >>
    >> So, that's slightly more confusing. Why should my 1Gb cards format to a
    >> different size to yours?

    >
    > It can depend on what the card tells the camera.
    >
    > More peculiar is that the odd one you are asking about is clearly not a
    > multiple of any valid blocksize for a FAT formatted disk (is there a
    > typo???)
    >
    > 1,036,042,240 = 16 x 1024 x 63235
    > 1,027,827,472 = 16 x 64239217 (most odd)
    >
    > I'd expect a cluster size of at least 1024.


    Martin,

    You're right, I had finger trouble.
    Correct figure is 1,027,817,472.

    ohn
     
    John Fryatt, Jun 29, 2006
    #7
  8. John Fryatt

    John Fryatt Guest

    Philip Bailey wrote:
    > John Fryatt wrote:
    >
    >> Sandisk tech. support aren't a lot of help either. Don't seem that
    >> knowledgeable about their own product, to be honest.

    >
    > That confirms what anecdotal evidence I've heard, too...


    I had another reply from Sandisk, saying that it might be a mapped-out
    bad block, but they strongly suggest that it's a hidden file put there
    by the OS. That can't right though as I don't see why the camera would
    put more hidden files on one CF card than another apparently identical card.

    I've often thought that companies have a few people who really know
    what's what with their products etc. but these guys are in some kind of
    'inner sanctum' and communicating with them is hard. The average help
    desk guy just doesn't have the detailed knowledge to answer many of the
    questions posed.

    Oh well, it's only a CF card. I think I'll give a it a good test though,
    before using it on something important.

    John
     
    John Fryatt, Jun 29, 2006
    #8
  9. John Fryatt wrote:

    > I had another reply from Sandisk, saying that it might be a mapped-out
    > bad block, but they strongly suggest that it's a hidden file put there
    > by the OS. That can't right though as I don't see why the camera would
    > put more hidden files on one CF card than another apparently identical
    > card.


    I've formatted all the cards both in the camera and with windows,
    and the "bytes free" numbers remain the same, but that one card
    STILL holds 2 fewer pictures.

    > Oh well, it's only a CF card. I think I'll give a it a good test though,
    > before using it on something important.


    Good luck!
     
    Philip Bailey, Jun 29, 2006
    #9
  10. John Fryatt

    ASAAR Guest

    On Thu, 29 Jun 2006 16:14:06 -0400, Philip Bailey wrote:

    :: from an earlier msg ::
    : After formatting in the camera:
    : 2G (bottom) card shows 65,536 used, 2,039,480,320 free
    : 1G (bottom) card shows 32,768 used, 1,011,367,936 free
    : 1G (side) card shows 32,768 used, 1,011,367,936 free
    :
    : I can't figure out how to show if there are any "bad sectors"
    : on a CF card, and I've been using both of the 1G cards for
    : more than a year with no problems. But SOMETHING must be
    : indicating to the camera that there's less available space
    : on the 1G (side) card...

    If there were a few bad sectors that weren't remapped, the free
    space would also be reduced. That apparently isn't the case. The
    camera has found some other difference between the cards that you
    (we) still haven't also determined.


    >> I had another reply from Sandisk, saying that it might be a mapped-out
    >> bad block, but they strongly suggest that it's a hidden file put there
    >> by the OS. That can't right though as I don't see why the camera would
    >> put more hidden files on one CF card than another apparently identical
    >> card.

    >
    > I've formatted all the cards both in the camera and with windows,
    > and the "bytes free" numbers remain the same, but that one card
    > STILL holds 2 fewer pictures.


    If you don't have a disk utility that shows the types of format
    and block sizes of the cards, try this. Immediately after
    formatting both 1GB cards, copy a very small file (less than 1kb but
    greater than zero would be ideal) to both of them. Then compare the
    remaining free spaces. It's possible that the cards don't have the
    same file allocation block size, and one is more efficient in
    utilizing disk/card space, while the other (if it were a hard drive
    and not a flash card) would have a slight speed advantage. The
    number of pictures your 20D thinks it can store on the card is only
    an estimate, and both cards might end up holding the same number, or
    the difference could be even more pronounced than the 20D's
    estimate. Since pictures vary in size, the only way to really know
    if there's a real difference would be to try to copy all of the
    pictures from one of the cards (when it's full) to the other card,
    and if they all copy, compare the final, remaining free spaces.
     
    ASAAR, Jun 29, 2006
    #10
  11. John Fryatt

    John Fryatt Guest

    John Fryatt wrote:
    > Hi,
    >
    > I just got a new CF card, 1Gb. When formatted in my camera it shows up
    > as 980Mb. The thing is, my other 1Gb CF cards all format to 988Mb. Why
    > should this one be 8Mb smaller? Assuming it's a bad block or some such
    > thing, would it remain stable that way, or is the card likely to
    > deteriorate?
    >
    > (Cards are all Sandisk Ultra II. Camera is Canon EOS 5D)


    Update...

    The vendor says that the card I bought is Asian spec. which is different
    from the European ones. That seems to make sense (to me, not being an
    electronics expert) - presumably the actual chips inside are different,
    resulting in a slightly different capacity. The 1Gb is only a nominal
    capacity of course, so it would still qualify as being 1Gb.

    The card seems to work fine, and I got it at a good price (eBay) so I
    guess that's it - sorted.

    John
     
    John Fryatt, Jul 2, 2006
    #11
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