The slider on the video tracks (in the left-hand box with the rest of the track controls) sets the opacity of the track. Slide them to the left, and they become more transparent, letting things from tracks below show through.
You can also do things like split-screen and such using Pan/Crop or the Cookie Cutter effect to get images from different tracks to show up together.
i have tried what you said and it does blend but its not doing what i expect it would do. what i am tring to do is stack multiple footage to increase the brightness level.
after duplicating 5 video tracks of the same footage and centring the level to 50% its not making any difference, what am i doind wrong?
I checked out your link, and have always noticed that stacking images makes them brigher ... I'd always thought of it as a bit of a nuisance, but now that I see the example on the website, it's given me some great ideas. Thanks for asking the Q, and providing that link, MrSleep!!