Nikon Coolpix 4200 Timestamp Irregularities

Discussion in 'Digital Photography' started by Top Spin, Jan 7, 2005.

  1. Top Spin

    Top Spin Guest

    This afternoon my wife and son took my Nikon Coolpix 4200 to look at a
    used pool table we are thinking of buying. On the way home, my son
    took the memory card out of the camera and put it in the card reader
    slot on his laptop and copied the photos to the laptop.

    When my wife got home, I connected the camera to my laptop with the
    USB cable. I noticed that the time stamps on photo files had some

    DSCN0037.JPG 01/06/05 12:12
    DSCN0038.JPG 01/06/05 12:13
    DSCN0039.JPG 01/06/05 12:13
    DSCN0040.JPG 01/06/05 12:14
    DSCN0041.JPG 01/06/05 21:56 ==> 21:56?
    DSCN0042.JPG 01/06/05 21:54 ==> 21:54? 2 minutes earlier?
    DSCN0043.JPG 01/06/05 12:16
    DSCN0044.JPG 01/06/05 12:24
    DSCN0045.JPG 01/06/05 12:24
    DSCN0046.JPG 01/06/05 12:24
    DSCN0047.JPG 01/06/05 21:56 ==> 21:56?

    I checked with my wife and the sequence according to the filenames is
    correct and they were all shot shortly after noon.

    I just checked the camera date & time and it is correct.

    Can anyone suggest what might be happening?

    Is the camera time unreliable?

    I got a new Nikon Coolpix 4200 about 6 months ago. I have used it on
    several trips. I have never noticed anything like this before.

    Top Spin, Jan 7, 2005
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  2. Top Spin

    Ed Ruf Guest

    Which time stamps are these? File system with camera just mounted on PC
    looking at contents of camera, or after transfer? How does this compare to
    the internal time stamp in the photo exif info? You might try reformatting
    the card in the camera once you've removed all the photos you want.
    Ed Ruf Lifetime AMA# 344007 ()
    See images taken with my CP-990/5700 & D70 at
    Ed Ruf, Jan 7, 2005
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  3. Top Spin

    Top Spin Guest

    Both. Using Windows Explorer, the time stamps are the same whether I
    an looking at the image files in the camera (F:\DCIM\100NIKON) or on
    my laptop's harddisk (C:\My Pictures\DCIM\100NIKON).
    Here's the list shown above with 2 new columns. The dates are always
    1/6/05 so I have only shown the times.

    1. The EXIF column shows the timestamp in the EXIF data according to
    IrfanView. There are 3 datetime fields in the EXIF data and all are
    identical for all of these photos.

    2. The Prop column shows the full timestamp (including the seconds)
    according to the Windows file properties. The Created and Modified
    fields are identical.

    Windows Explorer EXIF Prop
    DSCN0037.JPG 01/06/05 12:12 12:12:51 12:12:52
    DSCN0038.JPG 01/06/05 12:13 12:13:04 12:13:06
    DSCN0039.JPG 01/06/05 12:13 12:13:40 12:13:42
    DSCN0040.JPG 01/06/05 12:14 12:13:59 12:14:00
    DSCN0041.JPG 01/06/05 21:56 12:14:57 21:56:22
    DSCN0042.JPG 01/06/05 21:54 12:16:37 21:54:56
    DSCN0043.JPG 01/06/05 12:16 12:16:49 12:16:50
    DSCN0044.JPG 01/06/05 12:24 12:24:32 12:24:34
    DSCN0045.JPG 01/06/05 12:24 12:24:43 12:24:44
    DSCN0046.JPG 01/06/05 12:24 12:24:56 12:24:56
    DSCN0047.JPG 01/06/05 21:56 12:25:12 21:56:00

    This is very interesting. In only 1 case is the EXIF data the same as
    the file data. Is that because it takes the camera up to 2 seconds to
    write the data to the memory card?

    It looks like the EXIF data is reliable, at least for these 11 photos.

    Any ideas why the file timestamp is completely wrong for those 3
    I usually reformat the card after each upload. I am quite sure it had
    been reformatted not long before these photos were taken. It look like
    I also did a Reset on the camera because these photos started
    numbering at 0037.

    There was one other oddity this morning. I went to the date/time
    setting in the camera and noticed that it was about a minute slow. I
    sat the camera down for a couple of minutes and when I picked it back
    up, the camera time had not changed. It was now about 4 minutes slow.
    I was able to repeat this. It appears that while looking at the
    date/time setting in Setup mode, the camera clock is sometimes not
    updated. I don't see how this is related to the above because I doubt
    that my son was fiddling with Setup and in any case, those time stamps
    are off by 9 hours.
    Top Spin, Jan 7, 2005
  4. Top Spin wrote:
    The files are recorded using the FAT file system which only provides a
    five-bit field for the file time in seconds - it is coded as even seconds:
    i.e 0, 2, 4 .. 58s

    David J Taylor, Jan 7, 2005
  5. Top Spin

    Top Spin Guest

    There must also be something else going on, such as the delay time
    between when the photo is taken and when it is written to the memory
    card. Otherwise, I would expect about half of the file times to agree
    with the EXIF data. No?

    This camera does take at least a second between shots -- sometimes a
    good bit more. I thought I read somewhere that that was I/O time to
    the memory card.
    Top Spin, Jan 7, 2005
  6. It depends on the rounding algorithm used by the OS when it writes the
    file information to the directory. I've not done an analysis. It may
    also be that the EXIF data is timestamped with the time of taking, i.e.
    near the start of processing, and the directory timestamp is when the file
    is closed by the OS, i.e. near the end of processing. This would be
    somewhat consistent with your observed processing time.

    David J Taylor, Jan 7, 2005
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