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July 21, 2003

When Metadata Goes Bad

Metadata is one of those buzzwords that cause some people to swoon, and others to grit their teeth whenever it is mentioned. But the subject of this post is prosaic, not ideological.

My online photo album runs on metadata. Digital photos contain two types of embedded metadata: EXIF data set by the camera (date/time the photo was taken, exposure settings, etc.), and IPTC info (caption, keywords, copyright info, etc.). My photo album is run by a set of perl scripts which create thumbnails, grab dates and captions from the embedded metadata and use these to build web pages. The whole setup is nice, but assumes that the metadata is “good”.

A few days ago, I got, via email, some pictures of my son at preschool. The pictures were lovely. Unfortunately, the embedded EXIF date/time data was bogus. And that would have fouled up my photo album.

Though many allow you to view it, none of the usual image manipulation tools would allow me to edit the EXIF data. That’s because the camera is machine and, unlike people, can be presumed to produce reliable metadata. Except … when it doesn’t.

I ended up editing the JPEG files in vi to set the date/time by hand. I later found out that there’s a commandline utilty called jhead that lets you modify the "DateTimeOriginal" field (tag 0x9003) in a somewhat more user-friendly way.

Evidently, this is not an uncommonly-needed feature…

Update (8/1/2003): GraphicConverter 4.8 (my digital photo manipulation program of choice) has been released. It now lets you set the EXIF date via a context menu.

Posted by distler at July 21, 2003 2:31 AM

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