Indiana Jones and the Raiders of the Last Ark had some amazing 'ghosts' near the end of the movie (uhh...spoiler from 1980's?).
What many people might not know, however, is the really fun and (relatively simple) concept they used in order to achieve those effects.
With basically any camera or smartphone, a [even small] fish tank, a coat hanger, black poster board, and some cheesecloth (or even toilet paper if you're really strapped for cash!)...
...you can utilize the same techniques ILM did in many different films -- and it still holds up!