How I recolored 4K remaster of Terminator 2 to match original movie

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DATPHYR

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Published on June 6, 2024 4:53:21 AM ● Video Link: https://www.youtube.com/watch?v=oGGr9FXPeCQ

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Oi!
So I was working on some movie recoloring project.
You may know this movie - Terminator 2: The Judgment Day.
Short story: remaster of this movie was 'greenified' how I would call it.
In this video I'm trying to return original colors.

So, originally relaesed back in 1991, Terminator 2 is one of the most re-released movies.
There is 3 cuts of movie and 11 known releases on caps-a-holic.com.
And all of them have some issues.
Basically all pre-remasters are just low quality and all remasters are just green.

The green.
During remastering process Terminator 2 was re-scanned from film again.
Color grading was done from scratch, with modern technologies.
All colours moved to greens, almost like Matrix.
Some scenes have filters removed or completely reworked.
So that's pretty much another movie. Atleast colour-data wise.
Some says that greens are closer to Cameron vision, but yet I like original ones I've seen when I was a kid.
Original ones have some specific blue tint and crushed whites specific way.
It's way more metallic. It should be metallic, right?
So let's try to return them.

For this project I'm using AviSynth and it's plugins: libplacebo and ColourLike.
Side-off: You may ask 'what about Davinci Resolve?'.
Yes I have tried this software. It doesn't work like I want it to.
It can only match short clips. It can not work with whole-2-hour movie at once.
I want to make it one-shot, one big change.

Let's start with our 'star' - ColourLike plugin.
It's ancient plugin from 2005 and here is how it works:
You feed it videos and it creates files with colour distribution data across ALL frames and ALL pixels.
This process is not fast, runs at about 60fps on 1080p content and at about 30fps for 4K videos.
Then you feed it videos again + providing previously created colour distribution data files, 2 times, FROM and TO.
It calculates normalization curve and applying it to pixels.
Mathematically speaking after this amounts of colours in source and destination should be equal.
And they are, but .. not really.
You see, remember we was speaking about 'another movie'? That's it.
Since they differ in pan & crop, in overall filtering, in shading, balance, etc, etc - match will not be 100% accurate.
And I didn't even spoke about HDR-SDR stuff yet.
So what we can do with this?

Meet our next 'star' - libplacebo.
This plugin is modern and cool, I'm using it HDR-SDR tonemapping functions.
And it's updating! Which was crucial.
I'm actually doing this project for the second time.
Last time I aborted it cause of unpleasant results.
And how libplacebo helped me with that?
Well it's updated and now can tonemap SDR to HDR.
What I did is basically tonemapped my SDR pre-remaster source to HDR and then back to SDR.
This process balanced colours the same way like it's balanced on HDR remaster tonemapped to SDR.
So I collected colour distribution data from this 're-tonemapped' sources and applied it to my project and it works!

Ok, colours now way closer and feels way more natural, but we still have some issues.
Original footage is 10bit, but ColourLike can only work in 8bit (it's old, remember?), so we loosing data on this step.
What we can do with that? Well, we can perform matching few times with slightly different parameters and then average output.
My 'different parameters' was 4 tonemaps of HDR to SDR, made on 100, 101, 102 and 103 nits (I had to collect colour distribution data from each of them).
And I was able to do this only 4 times cause of hardware limitations of libplacebo.
So, libplacebo offering you 12 tonemapping functions, but realistically speaking after LONG research only 3 of them usable - bt2390, bt2446a and spline.
Each of them works differently, but in short:
- bt2390 have most contrast and may have crushed blacks and whites; overalls it looks good and vivid, and also some big companies using it;
- bt2446a have least contrast, but have 'everything covered' in colour shades; it also may be converted to HDR and back to SDR without noticeable changes, but looks bit dull;
- spline is somewhat in the middle, I like it more than others, BUT it have a big drawback - noticeable jumping brightness.
So each of them have strengths and weaknesses.
At first I was going to stick to spline and use only it in my pipeline, but results was unpleasant.
After long trial and error I ended up with this 'pretty basic' scheme:
[slide with block schemes]
- bt2446a for initial tonemapping HDR to SDR, cause histograms most filled after matching using it as first step AND also least crosstalk;
- bt2446a also used for re-tonemapping pre-remaster source, cause it will match highlights and shadows balance from both sides;
- bt2446a (yes, again) for tonemapping back from SDR to HDR, cause we used it in the first step so less disturbance this way;
- and finally, bt2390 (surprise) for tonemapping from HDR to SDR, cause HDR of previous step is actually a 'fake HDR' and also bt2390 is well known and common (madVR using it for example).