Rotorscoping
 

I did some rotorscoping the other day on a short video that my son shot. I used Premiere 6 and exported the video as a filmstrip. I then brought it into Photoshop 5.6LE did the rotorscoping and saved the project. I then imported it back into Premiere. In the source window of Premier the video looks fine but when I drag it to the timeline it needs to be rendered and after rendering it appears with horizontal lines through it. Has anyone any suggestions as to what may be the problem.
Thanks

It's hard without more detailed information.

I'm assuming you used progressive and not interlaced footage? Interlaced never rotoscopes very well.