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Re: [vox-tech] .jpg Mystery
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Re: [vox-tech] .jpg Mystery

On Thu, Jan 21, 2010 at 11:41 AM, Rod Roark <rod@sunsetsystems.com> wrote:
On 01/21/2010 11:18 AM, Bill Kendrick wrote:
> On Thu, Jan 21, 2010 at 10:35:35AM -0800, Bob Scofield wrote:
>> In Linux there are a couple of different ways I can get the date and time the
>> photo was taken.
> I picked a random photo I took with a Canon digital camera a few years ago.
> The date/timestamp of the file on my laptop was from 9:05pm on the day
> the photo was taken.
> However, using "File->Properties..." in Gwenview, and looking at the
> metadata stored in the file itself, it was stamped as 8:05pm of that day.
> I'm guessing the timestamp in the metadata is off by an hour because
> I never adjusted the clock inside my camera to account for Daylight Savings
> time change.  (In other words, the camera THOUGHT it was 8:05pm, so that's
> the metadata it stored.)

I would think that the file's timestamp is derived from the time set in
the camera, one way or another.  Either the camera creates the file on a
standard (probably win32) filesystem when the picture is taken, or the
timestamp is assigned from the metadata by some special software that
fetches images to your computer from the camera.

Sounds like some sort of bug to me, perhaps where some piece of software
neglects to take DST into account.
Sounds plausible to me.  Digital cameras attach metadata in an EXIF file, the exiv2 will let you read this file directly: http://www.exiv2.org/sample.html  Perhaps the machines.software interpret this file differently (i.e. DST stettings))
Of course there's lots of reasons a timestamp won't match reality: http://www.slate.com/id/2140303/ 


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Carl Boettiger
Population Biology, UC Davis
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