title: ImageMagick: How to get rid of TIFFWarnings/768 message about "Unknown field" when processing TIFFs?
body: <p>I process ETOPO1.tif into a cropped area hillshade. </p>
  
  <p>I get <a href="https://upload.wikimedia.org/wikipedia/commons/f/f2/Yug-Shadedrelief.tmp.tif" rel="noreferrer">a tiff image</a> looking like :<img src="https://i.stack.imgur.com/lES9c.jpg" alt="enter image description here"></p>
  
  <p>When I process it via ImageMagick, it runs successfully. But I get the following set of warning messages:</p>
  
  <pre><code>convert Yug-shadedrelief.tmp.tif -fuzz 7% -fill "#FFFFFF" -opaque "#DDDDDD"  whited.jpg     # lighter (0.9M)
  
   convert.im6: Unknown field with tag 33550 (0x830e) encountered. `TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/768.
   convert.im6: Unknown field with tag 33922 (0x8482) encountered. `TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/768.
   convert.im6: Unknown field with tag 34735 (0x87af) encountered. `TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/768.
   convert.im6: Unknown field with tag 34736 (0x87b0) encountered. `TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/768.
   convert.im6: Unknown field with tag 34737 (0x87b1) encountered. `TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/768.
   convert.im6: Unknown field with tag 42113 (0xa481) encountered. `TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/768.
  </code></pre>
  
  <p><strong>Is my .tif corrupted ?</strong></p>
  
  <p><strong>What can I do to take this messages out ?</strong></p>