If I paint a backgound for chroma key in photoshop(or corel painter)what DPI should it be for mini dv and hdv. I am very well versed in having talent seperate from the greenscreenlighting as well as haing seperate lighting as well for the talent so lets consider that is not an issue.
DPI is irrelevant to video. DPI is a relative measure to the real world (inches being a real-world measurement), and since your video should be displayed across the whole screen regardless of the size of display, a real world measurement has no relevance.
All that matters is that your video frame is the correct size for your format- 720x480 for DV NTSC, and 1280x720 or 1440x1080 for HDV.