How did Christopher Nolan Retain IMAX 70mm Quality After Post-Production?

(Source Reddit)

Today, I stumbled upon a detailed introduction to IMAX 70mm processing on the official Oppenheimer website (see reference below).

Now, the question arises: how do they achieve “full quality in their native format”? In other words, the final picture quality is exactly the same as the original image on the film.

If you have ever done digital post-production for movies, you should know that the output pixels must be the same or smaller than the input pixels; they cannot be larger (of course, you can use AI upscaling, but this is not “full quality in the native format” in the traditional sense).

So, if we use conventional digital methods to process IMAX 70mm, we would need:

1. A scanner that can scan IMAX 70mm close to 16k pixels. (It might not be exactly 16k in practice because film grains and various other conditions but this number comes from Oppenheimer promotional videos when they try to explain the digital equivalent resolution)
2. Editing software that can handle nearly 16k quality.
3. Add any digital special effects in 16k. This part is theoretically possible but it requires very high quality assets as well as a long rendering time. Note that Nolan mentioned multiple times they did not use CGI for…