The thing is you cant even see every frame, that's why most screencaptures are set to go from 40 to 60 fps.
Plus the events to paste everything into a canvas, and then use imagemanipulator to save it are going to really slow it down, especially if you have to wait a tick....
And yes you would still need to figure in timedelta in there somewhere.
Btw CamStudio is a free alternative.
http://camstudio.org/