35mm Scanning: DIY vs A Professional Service

[SiriusGen]

SiriusGen, if you still have that trailer, I will scan it for free, I'd like to see how our scan compares to the Spirit.

I have all three Terminator 2 trailers in film cans right here...

[poita]

I can swing one of those for free, so pick your favourite

[SiriusGen]

I can swing one of those for free, so pick your favourite

I've PM'd you.

[poita]

I've been asked many times now what happens when you send a film off to be professionally scanned, so I thought I would just briefly go through it here.

1. Once the film arrives, it is inspected by hand. Each reel is wound onto a lab core on an inspection table, and checked for any broken sprockets or other damage that needs to be repaired before the film is cleaned. This can take anywhere from 20 minutes to a few hours per reel, depending on the condition of the film. So for a 2 hour feature, that is on 6 or 7 reels, this process can take a day or two. The film is repaired if needed, and placed into an archive can, and an inspection report is written up, noting any issues and the state of the film.

2. New leader is usually then added to the head and tail of the film.

3. The film is then sent over for cleaning. It is wound onto another core, checked quickly once again in the process, and then loaded into the ultrasonic cleaner.
The film is moved slowly through a bath of warm perc, and the ultrasonics shake any dirt particles free, the film also goes through a set of spinning buffers that gently clean the film, and eventually it comes out of the cleaner, through a set of air-blades to dry it, and onto another core.
This process is also relatively slow, generally the slower the speed, the cleaner the film gets.

3. The film is inspected again to make sure there were no problems with the cleaning process.

4. The film is sent back to the scanning room. Then it is loaded onto the scanner, the drives checked for space, and the information logged.
The software is dialled in so that the settings are correct for density, stock type etc. and the resolution and bit depth and so on.
The film is advanced and the scanner focused, and a test scan done and checked.
For a triple flash scan, on say a Lasergraphics Director, each frame is exposed a total of 10 times. 3 sets of RGB exposures to ensure the full dynamic range of the film is captured, plus the infrared exposure to create the damage matte.
If the film is not perfectly flat, or has other issues, then the scanner is set to check and refocus every few hundred frames.
With 10 exposures per frame, the process is slow, even on the fastest scanners. A single reel typically takes 10-16 hours, so best case only one reel a day can be scanned, and that is assuming that there are no hassles with the scan. There can be situations where the scan fails for some reason, quite often due to a loss of tension, or a focusing issue, and then the scan is started again.

5. Once the scan is completed, the entire is scan is watched at a slow frame rate and checked for errors, then watched again at normal speed. This typically takes 3-4 times the length of the film, so a 2 hour feature will take around 6-8 hours to check. Any reels needing re-scanning are sent back to the scanner operator, along with notes as to which frames need rescanning.

6. Once the scan has passed the quality check, the film is wound back onto a fresh set of cores, loaded into archive cans and put into the film storage vault. The files are then transferred from the scanning computer onto a set of hard drives or LTO tape to send to the client. This process take a very long time as it is often around 17-30TB of data, and transferring that to LTO or HDDs typically takes an entire working day.

7. The drives/tapes are then verified, which takes a similar amount of time.

8. The drives are sent to the client, once they have verified the drives and data are okay, the film is sent back and the job is complete.

The process is very time consuming, and requires a lot of human handling and monitoring, and obviously only a limited amount of material can be fed through the triple flash scanners each week, so when a print arrives, it has to be fit into the schedule.

For single flash scanning, you can do real-time, although the other processes of cleaning, prep and writing out the files remains the same. Real-time scanning gives quite inferior results with theatrical release prints vs multi-flash, but single flash can work well for negatives that are not particularly dense.

So that is the process, it is also why triple flash scanning often has significantly longer wait times and costs a lot more money, not only is the scanner a lot more expensive than a single flash scanner, but it gets through a lot less footage per day, which means that expense takes much, much longer to recoup, hence the higher scanning costs.

[Valeyard]

Just a note, unless I'm mistaken "triple flash" means HDR (high dynamic range), not R-G-B. It's achieved by dimming and brightening the backlight for each exposure. So if you imagine scanning black and white film instead of colour, a HDR scan on a Director can be triple flashed (3x physical flashes/exposures) for the image plus (optionally) 1x for the infrared. It also has an option for double-flash or single-flash scanning too. The Arriscan has a "double flash" scanning for HDR, meaning 2x physical exposures per channel instead of 3x. The Scanstation's HDR is also double flash but with a bayer sensor not a mono sensor, and the film is moving so it is aligned "precisely" in software when merged. Scanners without a variable brightness back-light can't do HDR scanning unless they happen to have a sensitive enough sensor to do it in a single flash. To quote from the Arriscan XT brochure:

With a wide variety of negative, reversal and print material to be scanned, dynamic range is another key factor to image quality. ARRI’s unique double exposure method exposes each frame of film twice, at different light levels. Both of these images are digitized and composited into a single output image of exceptional quality.

In addition to providing more dynamic range, it also reduces digital noise:



There is also microscanning. Microscanning is only possible with a mono sensor that is specially designed for it, and I think it was originally developed for medical imaging uses. the image sensor is moved vertically and horizontally by mere nanometres for multiple captures, for medical imaging 9x captures is common (3x stops vertically and horizontally), but for film archiving the Arri imager and the Director's JAI imager are capable of 4x microscanning (2x stops vertically and horizontally). This also reduces digital noise when downsized to the native resolution, but of course slows down the capture as it requires 4x as many exposures!

Another interesting thing is, if I'm reading the datasheet correctly, the sprocket transport of the Arri classic/XT achieves significantly faster scanning than the sproketless option which can be used for badly damaged/fragile/shrunken film. I imagine the same would be true for the Director classic/10K or other scanners that have interchangeable film path options as well.

[spoRv]

For a triple flash scan, on say a Lasergraphics Director, each frame is exposed a total of 10 times. 3 sets of RGB exposures to ensure the full dynamic range of the film is captured, plus the infrared exposure to create the damage matte.

Just a note, unless I'm mistaken "triple flash" means HDR (high dynamic range), not R-G-B.

I guess poita means triple flash for dynamic (low,mid,high) for each RGB (red,green,blue) color, plus infrared.

[Valeyard]

Yes I expect so, but I thought I'd explain for everyone else. "Triple flash" is specific to certain scanners, what Lasergraphics does in 3x flashes, Arri achieves in 2x - this is only possible because they use a sensor that is designed differently.

[FrankT]

I have all three 35mm trailers for Terminator 2 Judgment Day, and had them professionally scanned. It was fairly expensive for just one guy doing his own project!

I used cinelab.london

Wait, they let you do that? They didn't say anything about copyright?

[Valeyard]

It's not illegal to scan private film without rights.

[ZigZig]

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