Hello - still learning how to use Premier Pro CC.  Question - I typically film in 4k.  However, I post my videos to Youtube (which only does 1920/1080p).  When I render the video - should I convert it over to 1080p since that is the highest that Youtube can display or should I render at the higher 4k?  Obviously 4k takes quite a bit longer which is why I am asking.  Another question - if youtube can only to 1080p - then should I just shoot in that video quality?  What is the purpose of 4k...is it just so that I have the video clips for when/if youtube or other sharing programs upgrade to 4k I'll be ready to post higher resolution videos?