Some JPG files does not have certain EXIF information. For EXIF tags that does not exist, Exif#[] seems to be expected to return nil. Instead, a random string is returned:
$ irb1.8
irb(main):001:0> require 'exif'
=> true
irb(main):002:0> Exif.new('IMG_20110205_142604.jpg')['Date and Time (original)'] # File without the tag
=> "\334+6\267\200\3174\267\001"
irb(main):003:0> Exif.new('IMG_20120914_194443.jpg')['Date and Time (original)'] # File with the tag
=> "2012:09:14 19:44:43"
$ irb1.9.1 -I /usr/lib/ruby/1.9.1/i486-linux
irb(main):001:0> require 'exif'
=> true
irb(main):002:0> Exif.new('IMG_20110205_142604.jpg')['Date and Time (original)']
=> "p\xE4V\xB7x\xE4V\xB7@\xB1\xFB\t@\xE4V\xB7\x02"
irb(main):003:0> Exif.new('IMG_20120914_194443.jpg')['Date and Time (original)']
=> "2012:09:14 19:44:43"
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: libexif-ruby 0.1.2-15
ProcVersionSignature: Ubuntu 3.2.0-26.41-generic-pae 3.2.19
Uname: Linux 3.2.0-26-generic-pae i686
NonfreeKernelModules: wl
ApportVersion: 2.0.1-0ubuntu13
Architecture: i386
Date: Fri Sep 21 19:44:18 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
PackageArchitecture: all
ProcEnviron:
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: libexif-ruby
UpgradeStatus: No upgrade log present (probably fresh install)
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