ADX spec for large format film

Discussions - ACESNext
1

Hi to all,

Was wondering if there was any plan to include an ADX spec for large format film. We recently asked to get some 65 (5 and 15 perf) plates scanned and it seems that it’s not possible because there’s no spec for it.

I would think that it wold most likely be the same as 35mm. Is this a correct assumption?

Any info would be awesome.

Thank you very much!

2

Hi Charles,

Most likely, the emulsion should be the same as 35. Arri have test films with virtually all modern emulsions and it is ran through the scanner and computed to make some kind of LUT. Using these allow to scan in ADX values. However, this exists only for 35mm on Arriscan. With a 65 mm scanner, you might be out of luck. One of the difficulty is to create those test films with a range of densities and colors. You need a film recorder to do this and that film recorder needs enough dynamic range to record on original negative (as opposed to intermediate neg).

Pierre

3

Thanks @pguerin ! Good to hear from you. Yeah… The 15 perf IMAX and 5 perf 65mm footage are to be scanned on an Imagica scanner. They most likely don’t have the data required. That being said, the imaging person at the lab did mention that there we’re no spec within ACES for this. @ACES : is there a road map for this? With the amount of stocks on the market it might be feasible to work on collecting this data? @pguerin does this need to be done more than once? Will the processing affect this?

Thanks!

4

Hi Charles,

The spec exists since a long time! 2008 in ACES and 2012 in SMPTE. The ACES document might be better as it has extra details and all the spectral data.
AMPAS Specification S-2008-002
SMPTE ST 2065-3:2020
The characterization has to be done once per stock per scanner. If I recall, it is based on spectral transmittance of the film and spectral emission of the scanner’s light. As I previously wrote, the challenge is to build a test film with a range of known densities and it is especially difficult with camera negatives that require a lot of dynamic range from the film recorder.

Pierre

5

Thanks @pguerin . I guess the spec has been around for a long time but it might not include large format specifically ? We all agree it’s pretty much the same… But, you know how “technical people” can get!? No spec… No Go. I’ll look into maybe getting this done with some partners. It would be great to have it!

Cheers

6

Hi Charles, the 65mm emulsions are the same as 35mm (and 16mm for that matter). ADX specs are exactly the same. Only the scanner and sometimes, its optical system, might be specific to 65mm.

Pierre

7

@pguerin Thanks Pierre! It would of been nice to have worked on this together at Technicolor! :wink:

8

The S-2008-002 is available as PDF in aces-dev repo in the v0.1.1 tag: aces-dev/docs at a83d10724316502e9c05851514a0ffa4b330a34a · ampas/aces-dev · GitHub. Interesting read…