Photos: decrease in quality when exporting a live photo as a gif
The GIF format was never designed to be for photos and by definition only allows 256 colours.
From Wikipedia, GIFs are used as follows:


  
  GIFs are suitable for sharp-edged line art (such as logos) with a limited number of colors. This takes advantage of the format's
  lossless compression, which favors flat areas of uniform color with
  well defined edges.[23]
  GIFs may be used to store low-color sprite data for games.[24]
  GIFs can be used for small animations and low-resolution video clips.[24]