[Jhsto]

It tries to predict patterns from blurry shots. It might introduce artifacts that were never there: some drawings I upscaled turned distant woods into houses. You can see why this might be bad when viewing something for historical accuracy.

See e.g., https://www.topazlabs.com and https://github.com/nagadomi/waifu2x

[feanaro]

Sorry, I think I was unclear. What I meant is that I am familiar with these techniques, I just never heard them applied in the context of history movies.