When WordPress is processing your images (the most common case is the simple thumbnails) it uses the library available on your PHP server (usually GD Library or ImageMagick).

The problem with GD Library is that it’s stripping away your image metadata when processing the images (one of the possible problems is the color rendering for photographers), if you want to keep them you need to ask you hosting provider the possibility to activate ImageMagick instead (this should prevent the striping of the metadata).