Full body apparitions, or casts, can be created by a single spirit or by a conglomerate of spirits to give the impression of being a single spirit. Each time that a spirit casts they use energy, so largely this is based on the amount of energy required to create the cast and how much energy the spirit has to use. Unlike humans, spirits do not require sleep but they do run low on energy and must “rest” in order to replenish their energy supply. Larger casts may require many spirits to work together as a conglomerate in order to cast the large image. (Also see Spirit Energy & The Celestial Body)
The cast in the photo above was done using smoke, but spirits can utilize nearly anything with which to cast including water, fire, vapor, mirrors, nature and virtually any reflective surface.