Titanic was shot on 35 mm photochemical film (specifically Eastman EXR 50D 5245 and Kodak Vision 500T 5279) in Super 35 format by cinematographer Russell Carpenter (True Lies, Avatar: The Way of Water) using Arriflex 35 III, Panavision Panaflex Gold II, and Panavision Panaflex Platinum cameras, with Panavision Primo spherical lenses, and it was finished on film at the 2.39:1 aspect ratio for its initial theatrical release back in 1997 (which included 35 mm anamorphic release prints, as well as 70 mm blow-ups).
Eastman EXR 50D 5245: https://125px.com/docs/motionpicture.../5245-1999.pdf
EASTMAN EXR 50D Film 5245 and 7245 is a low-speed
daylight-balanced color negative camera film with
micro-fine grain, very high sharpness, and high resolving
power.
Kodak Vision 500T 5279: https://125px.com/docs/motionpicture/kodak/5279.pdf
When you need the speed of a very
fast motion picture film, you also have to take the “baggage.”
A bit of compromise in sharpness. More grain than you’d
like. No more. KODAK VISION 500T Color Negative Film
gives you all the speed you expect. Plus, fine grain and high
sharpness you’ll find unbelievable.

More recently, Lightstorm has worked with Peter Jackson’s Park Road Post to optimize the 4K image in a hands-on and closely-supervised process that involved remastering the film scene by scene, and shot by shot—sometimes working on different areas within the same frame—to ensure that every bit of detail in the negative is visible, while managing but never eliminating organic grain (which, it should be noted, was intended to be very fine given the film stocks used).