As someone who actually works in film editing and has actually worked on projects that were not cut digitally, I will explain.
First of all, the first post that shows A/B rolls. That is only 16mm. Almost never used professionally for material shot on 35mm except in rare circumstances.
When they shoot a film, what is in the camera is the negative. Also called “Original Camera Negative” or OCN for short. Did you ever take still photos on a 35mm camera and when you get them back from the drug store there are “negatives” with your print? This is the pretty much the exact same thing that comes out of the 35mm film Panavision camera. The color values are reversed and the stock has an orange base.
What Richard, Marcia, Paul, Sean, and Duwayne actually “cut” on Moviolas and flatbeds are what is called a “one light” workprint. Meaning a color timer looks at the negative and strikes a print from it. He takes a best guess at what it should look like. Sometimes there are notes on the camera reports from the DP.
The editors cut away on these “one light dailies.” They try things: trimming, extending, swapping out takes. Over the course of the editing process, it gets pretty beat up. Occasionally the film will get massively scratched or shredded. A new print is struck of that shot (called a re-print).
Once the film is finished and they decide they aren’t going to change the picture cut anymore, the film editor’s “workprint” goes to the negative cutter. He takes all the OCN and carefully matches it to the reels they cut from the “one light dailies.” This is a meticulous process. Negatives are always handled very carefully. The “cuts” the picture editors make are done with scotch tape. The negative cutter does “hot splices.” which basically fuses the two pieces of film together. Obviously if the editor cut a scene, and then decided to extend a shot (which happens a lot) the workprint will have a splice in the middle of a shot. The negative cutter will not replicate that cut. He matches the cut perfectly because all film negative has “key numbers” on the edge of the film. He matches everything by numbers.
Once you have the master negative reels, this is where IPs and INs come into play. Not really before. From the cut OCN reels, several Interpositives are made. This is basically making a positive print (proper color values) but it is on orange negative stock. From each of those IP’s several Internegatives (INs) are made. INs are basically copies of the Cut OCN master reels, but they have the final color timing baked in. And there are no splices. From each of them several “release prints” are made. Ultimately thousands of them. How many IPs and INs are struck depends on the size of the release. A studio usually tried to get at least 200 “Release Prints” out of a single IN. For large “premiere” venues in major cities they may strike what are called “EK Prints” directly from the Cut negative. “EK” stands for “Eastman Kodak.”
Now in terms of VFX, that is another can of worms. When you cut VFX movies, typically you want to get VFX heavy scenes done first. It is very expensive to have to do VFX over. Nor do you want to shoot a 10 second shot and then scrap half of it because a scene got trimmed. That’s money wasted. And the VFX guys need as much time as possible to do their work. That still applies today with CGI VFX. But in the photochemical world, let’s say you have as shot with two elements. You will strike IPs for both those shots. The IPs will only be the section used in the cut with some “handle.” In film it would be 1-5 feet. (3 feet = 2 seconds).
These will be run through an optical printer. Which is basically a camera mounted against a projector. The two elements run through the projector side optical printer - one at a time. One one piece of new unexposed 35mm negative will be run two times through the camera side. This will create a new piece of negative with new key numbers which is often called “Dupe Neg” or “Optical Neg.” And like a xerox copy or a dub of a cassette, there will some quality loss. That is why VFX elements are often shot on large format film. It mitigates quality loss. ILM used “VistaVision.” When Richard Edlund left and started Boss Films, they did everything on “65mm” film.
A one light print is struck from this new negative. And assuming everything went right, it goes to the cutting room and they “eye match” it into the workprint. Basically matching the action by looking at individual frames. I massively simplified the process of photochemical VFX.
And almost everything I have described - is a relic of the past. Very few movies are shot on film. And almost none are finished on film anymore. But this is how it was done on the original trilogy.
I realize this thread is several years old. But hopefully someone is out there listening…