DV Info Net - Light leak overlay/transition?

Light leaks are usually video clips that you lay ontop of your footage and then use composite modes to remove the black background (usually screen mode for the most natural effect, but other modes will give uniquely useful results too) to blend it with the footage below.

The actual light leaks clips are available for purchase from some stock effects providers, or you can make your own. Using a camera with interchangable lenses (DSLR's are perfect but it will also work with an EX3 or similar), remove the lens and hold the lens cap up against the mount. Then wiggle the lens cap around to let just a small amount of light in the edges. This may work with fixed-lens cameras too, as long as you throw everything out of focus first - I'm not sure though as I haven't tried it. You can get different variations by doing this near direct light sources, indirect sources, multi-coloured light sources, silhouetted objects (venetian blinds, for example), fast moving backgrounds, etc, etc. The advantage of doing it yourself is that they will look unique - the stock effects are often overused and easily recognised.

You can use the same clips as overlays or transitions - although you might find they work best as transitions if they fill almost the entire frame, almost like a film flash or dip-to-white transition.