Exif Timeline Comparer

Idea of a tool I want:

Suppose k friends (k>1) join an event (a party, a trip, whatever) and everyone is taking photos with a digital camera. Afterwards they put all their images into a common folder. Unfortunately, the images are sorted alphabetically, so first come all photos from Bob beginning with DSC, then all from Alice matching IMG*. Wouldn't it be nice if all photos would be in chronological order?

Well, fortunately jhead has an option to rename an image after EXIF time:

  jhead "-n%Y%m%d-%H%M%S$friend" *.jpg

where $friend is the name of each friend applying this command.

The group knows that there cameras clocks are not very exact and every clock has a difference from "real time" of up to an hour. Therefore everyone takes a photograph of a (digital) wall clock, calculates the difference of wall time minus exif time and adjusts exif time with calling


jhead "-ta$WallMinusExif" *.jpg


But what are they doing if they forgot to synchronize with wall time and already shared the photos (and reset their camera's time)? That's what I want to have a tool for! What information can the friends extract from their photo streams? At least they can say for sure that some event was before another one.

Say they took a trip to Paris and first saw the Eiffel tower (shot by Alice), went on to a cafe (where Bob took photos) and then to the Seine (where Alice took photos again). Now they want to tell for all events which one was before/after which and calculate a minimum time difference out of this information.

After that, they can tell that Bob's time adjustment (relative to Alice) is between 4 and 7 minutes, and they decide on the middle: 5:30min.