I cannot figure out how to superimpose 2 shots. What I want is to show 2 shots at the same time to realize "ghost-like" effects. I am able to do it with a real 16 mm camera (rewind film, expose it again with a lower f stop), but how does it work with final cut?

Thanx a lot

You just have to overlay two video tracks and set them at different percentages. If you didn't move the camera between both action sequences, this should theoretically work. I've never tried it myself, but it should work if you set the "ghost" video at like 50% and the normal shot at like 75%

Simply put whatever video tracks you want on top of eachother in the timeline, then while still in the timeline, doubleclick the top track so that that track is in the viewer. Then click the motion tab in the viewer and go down to opacity and adjust the percentage, anywhere between 50 and 80 would look good.

if you're going for a gost look, you may want to experiment with the compositing method in addition to lowering opacity. Try screen or add.

oh lol thank you a lot I am still a novice with this software

but another question...I've seen dreamlike sequences where the outher part of the frame were confused and out of focus but the inner part perfect. Something like in DARK CITY as an example. Any idea how to do that?

If you're talking about wht i'm thinking, then it's also in the motion tab. Click the edge feather box and adjust from there.

In FCP, you'd need to double sources on top of each other (same footage on v1 and v2). Then apply a garbage matte, feather the edges, and apply a blur to one layer. This would give you control (via the garbage matte) where the blured area is affected.
COPS uses the same technique to mosaic faces so you can't see the innocent (if there is such a person).
joren