¿Did you ever wonder how Disney did the ChalkDrawing Scene in Mary Poppins with BlueScreen? The answer it did not. Instead, Disney invented the SodiumProcess:

0thly, I must explain how Blue/Green-Screen work:

One designates, a color, with film, blue because the GrainSize is smallest and with digital cameras, green because the BeyerFilter is half green pixels (the full-color pixels come to be from interpolation, initially linear, post 2000 using bicubic interpolation, and, nowadays, using AI) with the color used to create an AlphaChannel for compositing. This works but one has to fightthe alphachannel in postproduction.

As an aside, I know that some in this group like Star Trek. ¿Did you notive that, in the TOS-Movies, the Enterprise looks best in Star Trek Ⅰ: Star Trek The MotionPicture? That is because the finish on the Enterprise was Opalescent:

The reason the Enterprise does not look as good in the other TOSMovies is because every frame with the enterprise required retouching by hand because the finish reflected the light from the BlueScreen. This was okay for the 1st movie but not the sequels because their budget, adjusted for inflation, was half the first movie:

The idea was to invest in the 1st movie and then economize by reusing prps, sets, costumes, models, et cetera. This workedworked great except for costumes because the costumes in the 1st movie were an hastle. Adjusted for inflation, the sequels did cost about half as much as the 1st movie, but the Enterprise had to be repainted because the sequels just did not have budget for hand-retouching every frame with the Enterprise in it.

Disney figured that if it would use a pure color, it could more quickly, cleanly, and easily composite. Sodium has 2 spectral lines very close together which can be filtered. Now it is time for another aside:

I hate LightPollution. We used SodiumLamps for lighting roads. we could filter the yellow light and see the stars. Now, we use BlueLEDs with a phospore for generating white light which is all over the specrum, thus practically unfilterable. So much for astronomy

The trouble is the prisms for splitting out the SodiumLines:

The 1st 1 cost over a myriad (a myriad is 10,000) dollars in 1960s dollars to produce, but that was just a prototype. They made another 1, for a myriad dollars. Then they made a 3rd 1 for a myriad dollars. ¡The process does not scale!

Disney stopped making these prisms for splitting out the SodiumLight and used these 3 prisms in the 1960s, 1970s, and 1980s. The SodiumProcess is what made the ChalkDrawing Scene in Mary Poppins possible.

Modern VFXArtists decided to try the SodiumProcess with modern technology. ¡It blows GreenScreen out of the water!:

I wonder ¿whether this experiment in low-cost SodiumProcess is an 1-off? or whether the new low-cost SudiumProcess will catch on and become the new norm? We, with the fullness of time, shall learn.