title: How to modify TIF file's EXIF data
body: <p>I am trying to modify existing metadata within python 3. More specifically I have GPS coordinates and altitude in a my metadata, and I need to modify it. </p>
  
  <p>I'm using piexif mudule, and I ancounter two problems. 
  First, I managed to change Altitude, using 
  <code>exif_dict['GPS'][piexif.GPSIFD.GPSAltitude] = (140, 1)</code>
  and it works.</p>
  
  <p>But I can't understand how to change Latitude and Longtitude? as they consist of three fields, like ((53, 1), (291191, 10000), (0, 1)).</p>
  
  <p>The second problem occurs when I try to save tiff file with modified metadata. If I save it as TIFF file: 
  <code>img.save(fname_2, 'tiff', exif=exif_bytes)</code>, 
  the fname_2 file is created, but it's metadata isn't changed. If Isave as JPEG - 
  <code>img.save(fname_2, 'jpeg', exif=exif_bytes)</code>
  - metadata changes, but the file is compressed from 289 MB to 15 MB, that makes it impossible to use it for my purposes.    </p>
  
  <p>Has anyone managed to do this? It sounds like it would be very simple, but I can't seem to work it out.</p>
  
  <pre><code>import piexif
  from PIL import Image
  Image.MAX_IMAGE_PIXELS = 1000000000
  
  fname_1='D:\EZG\Codding\photo\iiq/eee.tif'
  fname_2='D:\EZG\Codding\photo\iiq/eee_change.tif'
  img = Image.open(fname_1)
  exif_dict = piexif.load(fname_1)
  
  latitide = exif_dict['GPS'][piexif.GPSIFD.GPSLatitude]
  longtitude = exif_dict['GPS'][piexif.GPSIFD.GPSLongitude]
  altitude = exif_dict['GPS'][piexif.GPSIFD.GPSAltitude]
  
  print(latitide)
  print(longtitude)
  print(altitude)
  
  exif_dict['GPS'][piexif.GPSIFD.GPSAltitude] = (140, 1)
  
  exif_bytes = piexif.dump(exif_dict)
  img.save(fname_2, 'tiff', exif=exif_bytes)
  
  the fname_2 file is created, but it's metadata isn't changed
  </code></pre>