The apparition reveals itself- in Raiders of the Lost Ark (1981)
Industrial Light & Magic went all-out on the final effect scene in Raiders of the Lost Ark. There are so many wonderful moments in that sequence - melting heads anyone? - but the one that freaked me most out when I was a kid was this one:
At first the ghostly apparitions seem sort of nice, but suddenly things take a turn for the worse when this beautiful creature turns into a deadly skeleton. Most of the ghosts were small figures shot in a water tank to give them that otherworldly floating look. This particular ghost, however, was a real actress (Greta Hicks). She was suspended on wires, dressed in white, and covered with white makeup. Hundreds of feet of film was shot until just the right bit of footage was captured.
Then a mummified skeleton was brought in, dressed up to look like the actress, and carefully lined up in camera. The transformation was done with a simple dissolve between the two images. Finally the footage was rear-projected in a water-tank to achieve the "blurry" effect.
The optical department then had the arduous task of putting the final shot together. They did an outstanding job, creating a truly classic, magical shot. An evil magical shot!