title: EXIF python PIL return empty dictionary
body: <p>I can't figure out why _getexif() returns an empty dictionary. I know that the image contains EXIF data as shown by ImageMagic :</p>
  
  <pre><code>&gt;&gt; identify -verbose image.jpg
  
  Properties:
      date:create: 2015-01-12T16:20:26-05:00
      date:modify: 2013-07-01T14:05:08-04:00
      exif:ColorSpace: 1
      ...
  
  exif:Model: PC800 PROFESSIONAL
      exif:ResolutionUnit: 2
      exif:SceneCaptureType: 0
      exif:WhiteBalance: 1
      exif:XResolution: 72/1
      exif:YCbCrPositioning: 2
      exif:YResolution: 72/1
      jpeg:colorspace: 2
      jpeg:sampling-factor: 2x1,1x1,1x1
      signature: e63fcbacdfd031e611b83befaa4a9c8ef6235894da10784a692f90832205ec60
    Profiles:
      Profile-exif: 931 bytes
  </code></pre>
  
  <p>Now try to read EXIF with python2</p>
  
  <pre><code>img = Image.open('image.jpg')
  &gt;&gt;&gt; img
  &lt;PIL.JpegImagePlugin.JpegImageFile image.jpg mode=RGB size=2048x1536 at 0x7FEDF2E8A518&gt;
  exif = img._getexif()
  &gt;&gt;&gt; exif
  </code></pre>
  
  <p>returns nothing...</p>
  
  <p>I also tried with pyexiv2, same result:</p>
  
  <pre><code>&gt;&gt;&gt; import pyexiv2
  &gt;&gt;&gt; metadata = pyexiv2.ImageMetadata(img)
  &gt;&gt;&gt; metadata.read()
  &gt;&gt;&gt; metadata.exif_keys
  []
  </code></pre>
  
  <p>Any ideas why I can't read theses exif data into python ?
  Python 2.7.8 (default, Sep 24 2014, 18:26:21) on Arch Linux.</p>