Comment by KaiserPro | Hacker News Reader

Comment by KaiserPro | Hacker News Reader

Aha! I used to work in film and was very close to the film scanning system.

When you scan in a film you need to dust bust it, and generally clean it up (because there are physical scars on the film from going through the projector. Theres also a shit tone of dust, that needs to be physically or digitally removed, ie "busted")

Ideally you'd use a non-real time scanner like this: https://www.filmlight.ltd.uk/products/northlight/overview_nl... which will collect both colour and infrared. This can help automate dust and scratch removal.

If you're unluckly you'll use a telecine machine, https://www.ebay.co.uk/itm/283479247780 which runs much faster, but has less time to dustbust and properly register the film (so it'll warp more)

However! that doesnt affect the colour. Those colour changes are deliberate and are a result of grading. Ie, a colourist has gone through and made changes to make each scene feel more effective. Ideally they'd alter the colour for emotion, but that depends on who's making the decision.

the mechanics are written out here: https://www.secretbatcave.co.uk/film/digital-intermediary/

How much of the colour change is also dependent on the film printer and also film scanner/telecine?

It just seems like there’s a lot of variability in each step to end up with an unintended colour, that will taken as the artist’s intent.

Any digitizing is done before color grading.

All steps before try to not affect the color and keep as much dynamic range as possible to give as much leeway as possible for the colorist.

Realistically, for Pixar and Disney (not people with limitwd funds, say), the color grade is much much more relevant to the final color than the specifics of digitizing.

> is also dependent on the film printer

The printers deffo make a difference to colour, but I came from VFX world where we put a macbeth chart in for each shot so we could adjust the colour afterwards. (https://en.wikipedia.org/wiki/ColorChecker) We'd have a whole team working on making sure that colour was accurate.

The scanners we used (northlight) were calibrated a lot so my understanding is that if you scanned the same film twice it was meant to be pixel perfect (We did rescans for various reasons and it supposedly matched up enough to do effects work. but that might have been proxies, ie low resolution scans that were done for speed)

Also the printers should, if they are good match it properly, thats what you're paying them for. I know that we did have a person that calibrated film projectors for colour, but I never asked them _how_ they did it.

For toy story its a bit harder because you are digitising a whole finished movie, you don't have the colour chart in every shot to keep the colour consistent. I know for adverts the telecine people did loads of fiddling to make the colour consistent, but I assumed that was because the spirit 4k was a bit shit.

I never dealt with actual finished prints, because the colourist/DI people sent the finished graded off to someone like Deluxe to print out

Thank you! I would love to know the process of the colour guy. Like how much of it is the same as a chef tasting a dish and realizing it needs x ingredient in the spot.

I recommend interviews with Roger Deakins, like https://m.youtube.com/watch?v=w56rFxPyZno

Doesn't wet scanning "automatically" get rid of the dust and scratches issue?

> However! that doesnt affect the colour.

That has been something I've wondered about since seeing frame comparisons of (probably) telecine'ed prints of The Matrix vs. the myriad home video releases.

I'm a colorist and it absolutely does effect color. Every telecine is different and will create a different looking scan. Telecine operators will do a one light pass to try and compensate but any scan needs to be adjusted to achieve what the artist's original vision was.

> Every telecine is different and will create a different looking scan.

I mean they should be calibrated, so they have a different feel, but they shouldn't be wildly different like the screen shots.

I know the spirit operators did magic, but they were in the advertising team, and I was in film so I was never allowed to visit the sexy telecine room.

I was going to mention the Noodle video on that

https://www.youtube.com/watch?v=lPU-kXEhSgk

TL;DW, different physical rolls of film sent to different movie theaters can have slightly different coloring, if they were done by different people or different companies or even if someone just did their job differently that day. Film color was not an exact science and not always perfectly repeatable, and depended on chemistry.

How did you dust bust it? Wipe it by hand with a microfiber cloth or something?

In optics & film usually blowing air is employed, as wiping runs the risk of further scratches in the case of an abrasive particle (e.g. sand)

There are handheld tools (google hand blower bulb), but I would imagine film scanning uses something less manual

Agreed. That was just a starting point for the convo. Seems like any reasonably fast method would either result in damage from particles or would be incredibly slow. Sometimes a blower doesn't do a complete job.

> Theres also a shit tone of dust, that needs to be physically or digitally removed, ie "busted"

Is that because you're just leaving the film out in a big pile, or because it decays rapidly?

I would have expected film to be stored in containers.

Someone correct me if I'm wrong, but I believe it builds a static charge as it runs through the projector and attracts dust. I say this because I remember holding my hand near moving film in our (home) movie projector, and as a kid enjoying feeling the hairs on my arm standing up from the static. Maybe professional gear protects against that somehow, but if not that'd be why.

Yep, most film (also photo) attracts dust like a magnet. Kodak made a Static Eliminator to mitigate that with high voltage to an extent:

https://mcnygenealogy.com/book/kodak/static-eliminator.pdf

It's normally stored in sealed boxes, but every time its taken out to be projected then the whole reel is unspooled and exposed to the environment. Most projectors are pretty good at not blowing unfiltered air on the film, but there is a surprising amount of dust that is just floating in the air.

The room that the scanners used to be in were temperature and dust controlled, everyone was supposed to wear dust jackets when you enter.

Film is only 35 mm or 70 mm large, and the picture itself is slightly smaller than that. Even a tiny amount of dust adds a lot of noise.

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