Quicktime renders has horrible quality after render (animation)

[Dawid30521933189t]

Hi, 

I have problem with rendering with transparency, only resolution I found till today is to render as png sequence, but it's so unpractical.
Every tutorial at Youtube etc. shows to render videos with alpha channel in QuickTime, so I did - but every single render looks horrible, but in preview it's just perfect.

Preview:

After render:

[Ann Bens · Accepted solution]

No wonder it looks awful.

You are trying to blow up the image from 640x360 to 1920x1080.

You cannot enlarge an image without quality loss.