Video restoration techniques ???
We know that film degrades in predictable and unpredictable ways, with chroma shifts for red, green or blue, and it seems there is a different shift at different exposure levels.
So, what techniques approaches do you all find yourself using, or what considerations are top of mind when given a project such as a 1950's era color film that has been scanned at 2K and 422 ProRes. That is, the digital copy is probably about as good as one might expect for this project.
But surely people who have done this a lot have their own preferences and approaches.
For example, there is an FX option in Studio for color balance, which looks as regions or the entire frame with respect to white balance and exposure. This, so far, seems to be a good first step to get things within range.
But there are some odd and very distracting color shifts seemingly dependent upon the level. Could be a lot of power windows and filters.
[Michael McCune] " a different shift at different exposure levels."
Film is about density. Which is a power/log transform.
I wouldn't say the ProRes codec is a problem, per se... but it's going to limit what you can do, to a certain extent.
If the option was there to pull the scan in a 444 codec, with a transform profile (ACES), I might have opted for that. In any event, working in the Academy color space with an appropriate IDT might give you some wiggle room.
If you are dealing with faded layers (remember color film is a gel sandwich) then maybe think about simulating a Technicolor 3-strip approach. Set up a splitter node and assign a grade path for R / G / B. Work the curves. Look for shading errors... sawtooth, parabola...
If you for some reason have a China Doll at the head, pay some attention to it. If your roll of film has been sitting in a can for a couple of decades, there is a chance that the outer wrapped footage is more faded than the inner, so anticipate that the image will not be entirely consistent throughout.
I used to deal with film that in some cases was more than 70 years old, and did not have the tools currently at our disposal. What I would have given...
"I always pass on free advice -- its never of any use to me" Oscar Wilde.
Every film restoration project is different. You could theoretically attack each shot with separate RGB splitter/combiner nodes and find a way to minimize the flicker on each channel, perhaps using the de-flicker tools available within Resolve (or plug-ins like BorisFX BCC).
In truth, if you want to do this right, I think you need very specific film restoration tools like the ones available in MTI Film, Pixel Farm, Algosoft, or Diament HS-Art. This is very difficult, meticulous, frame-by-frame work that can be challenging and time-consuming even under the best of circumstances.
o my.. you're hosed. prores is not DPX log, EXR half float, or Tiff 16bit. you need at least 16 bit capture or your throwing away dynamic range below 16 f-stops. maybe its 8mm? lol.
I forgot to mention about the curves. they will be your friend. After black point, white point. set gamma with exclusion to a certain ire so all shots match gamma.
Each shot will have custom rgb curves. to normalize them fast, luma key mask part of the shot at a time.
blacks, shadows, midtones, highlights, white point. the vectorscope will show you if its in the middle and neutralized, allowing you to focus on one part at a time.
now all will be perfect. you can grade after all shots match.
[Chris Wright] "o my.. you're hosed. prores is not DPX log, EXR half float, or Tiff 16bit. you need at least 16 bit capture or your throwing away dynamic range below 16 f-stops. maybe its 8mm? lol."
For a lot of old film, I don't think you're right. I think the film itself is hosed. And I've worked on literally hundreds of film restoration projects. Given lots of time and money, I'd absolutely choose 16-bit DPX, but it's not always possible from a time and money point of view. And there's dozens of ways to color-correct it, not all of them using curves. A lot of film made before 1980 is not going to have nearly the dynamic range you might think it has on paper. Real-world, it's just not there -- it's all noise and grunge.
The real problem is dealing with the damage, unsteadiness, flicker, uneven grain, and density shifts within the frame. For that, you pretty much need some kind of pixel-by-pixel mapping within each color channel. And that's pretty specialized software. We had a ton of flicker and density shifts on the 1977 Star Wars (when I was on the restoration team at ILM in 2004), and it took a team of about 20 people to solve those problems. The color correction was the easiest part; it was the everything else that was the problem. That was a DPX job, unfortunately only 2K, but I expect the film's new owners will do a new 4K scan and do a much better job.