After no little fuss and bother, I was able to find yet another DVD of Fellini's 'Orchestra Rehearsal' and grabbed the following snapshots using VLC Media Player which is all I've got for video capture on this machine.
For those who are interested, the scenes which include the lovely 4-group Gaggia and the Barista run from 36 minutes to roughly 38:30 on the DVD release.
Here's a shot of the Barista and his 4-group side-lever Gaggia - note that the number 3 group is apparently jammed with its lever forward, a very common problem with these machines due to uneven piston wear - also note the grinder full of 'North Italian' roast - a decent cinnamon color, not the inky black beans sold to Americans as 'espresso roast.'
Here's an establishing shot with the 4-group Gaggia in the background - sorry for the poor quality and obstructed view - it's the best I can do at the moment:
In this shot, you can just barely see that the Barista has brought the lever down into the pre-infusion position and holds it there for about 4-5 seconds. Early Gaggias had no pre-infusion detent, you just held them down - later ones added a notch in the operating cam, but since it soon wore smooth, no one relied on it and continued to hold the lever down.
Now, the Barista brings the lever up out of pre-infusion and raises it about 1/4 of its stroke in a move which is basically a rocking motion 'Lower, hold, hold, hold, raise, lower, release.'
Up it goes:
And release to let the spring complete the pour:
As a side note for you true lever-freaks, the Gaggia, Astoria, Riviera, and Elektra spring-lever groups are all decoupled designs, where the piston and spring are compressed by the lever acting on a cam. This means that while you can slow down the extraction by retarding the lever's rise, you cannot speed up the extraction by lifting the lever because there is no direct connection between the lever and the piston.
OTOH, Victoria Arduino, Faema, and Conti machines do have linkages which directly connect the lever to the piston and hence they act more like a Pavoni or Olympia machine in that you can have very precise extraction control by retarding or raising the lever.
I hope that these pictures are of interest to folks here - given that Fellini took pride in using real people doing real work, and given the obviously well-used condition of the machine - I have little doubt that we've been given a very rare glimpse of a 'Golden Age' Barista doing what he did every day.