A dissolve is a transitional device in which one shot fades out while the next shot fades in, so it is briefly superimposed over the first and then replaces it altogether. Dissolves are also called “lap-dissolves” or, in England, “mixes.”
The first use of the dissolve in film may be in the George Méliès film, Cendrillon (Cinderella, 1899). The early dissolve was relatively easy to implement in camera. One would simply stop the camera, roll it back, and begin exposing the next shot. There was no action continuity across this transition until 1904, when Méliès used the technique for a wolf-man special effect in le Roi du maquillage.
Edwin Porter and others picked up Méliès’ use of the dissolve, but in time, the straight cut became the most common way of joining shots within a scene, and the dissolve was used within the continuity system primarily to suggest a change in location or time – or to suggest a flashback or dream sequence.
In Citizen Kane, however, some dissolves also convey the movement from a narrator’s retelling of a Kane story back to the film present, which imbues the dissolve with the psychological inflection of an unreliable narrator. In David Lynch’s Lost Highway, dissolves are extended to the point of verging on superimpositions, evoking a psychological blurring of time while driving. And in The Men Who Tread on the Tiger’s Tail, Kurosawa uses a series of sequential dissolves to denote Benkei’s increasing drunkenness. So the dissolve carries with it peculiar psychological associations. In fact, dissolves have been used to build associations between images, as in the dissolve from Janet Leigh’s eye to the drain in Psycho, or Maya Deren’s dissolves throughout Meshes of the Afternoon.
Dissolves have become somewhat less common, though they were and sometimes still are used to hide jarring cuts – especially before jump-cuts became widely acceptable film grammar. This practice led to a saying common among editors: “if you can’t solve it, dissolve it!”