alt Hacker NewsClose Encounters of the Third Kind was indeed when I first noticed this effect. It was dramatic and cool and all that, but pretty obviously an effect. Coupling it with Raiders of the Lost Ark and the effect almost pigeon-holes a film to be of that era.
I'm unsurprised Douglas Trumbull was behind the Close Encounters effect since his work on 2001: A Space Odyssey captured his earliest experiments filming tanks of liquids with fluids added. They were fairly effective in Kubrick's film when they appeared to resemble fantastic nebulae, globular clusters…
(And never mind the mind-bending cleverness of how the slit-scan shots were created for 2001.)
Growing up my mom pointed out that she could tell it was a Spielberg movie by the cloud effect. It wasn't until I was older and rewatched them to see she wasn't wrong. I'm pretty sure it was the first time I learned about little signatures like this, or how a director will use the same camera move in every movie. But the Spielberg clouds was one of the things that really got me interested in the magic of movie making.