So for a fair bit now, I have been trying to loosely piece together a way of adjusting the overall contrast and white balance of a film negative scan (altering the scan's DMax to reflect something based off of the stock's Status M graph) before doing the traditional printer offset styled color grading and then running it through a PFE to get the final image.

I understand this all isn't really possible to distill into an exact science given how wobbly photochemical work is and all that, but when I am given scans that have wildly incorrect levels and balances, I'd like to try and ballpark them as close as I can to get something consistent.

However, recently I came across a peculiar quandary regarding this process, which is that apparently depending on how a negative is to printed, the expected input printing density is altered to reflect this output.

Between the relatively standardized SMPTE RP 180 printing density and ACES' ADX / APD, Kodak apparently averaged in the past what printing density is expected for printing on their stock, as well as what is to be expected when printing to Fuji.



So unless I am horribly misunderstanding how this process works, my main question is what sort of density input is expected for the PFEs that are built into ColourSpace?

According to the manual stuff floating on the LightIllusion site, it just vaguely describes that it expects a Cineon input, and for the Film Profiling services, it makes note of both SMPTE RP 180 and APD. But does that mean that the input LOG scan should be altered to reflect what that particular stock expects (Kodak for Vision & Premiere, Fuji for Fuji), or does the LUT expect the standard SMPTE RP 180 or ADX / APD measurement and automatically alters the input?

Alternatively, is there any sort of rule of thumb that could be derived from a film stock's Status M measurements when working with a scan that is completely off the mark?

Thank you in advance!

The film profile data within ColourSpace is the extraction of data from both the relevant film negative and print, performed via one of our specTD hybrid spectrophotometer & densitometer.

The film profile data can be used to generate LUTs for any video image input from a telecine or film scanner.
The video image will by default be a log image, as that is what all telecines and scanners tend to be calibrated for.
The colour gamut required is defined by the terged out colour space - Rec709/P3/etc..

https://lightillusion.com/look_luts_design.html

Steve

Steve

I understand that scanners automatically output some form of LOG, but never remotely consistently. I've had a negative reel of a trailer scanned twice and both scans came out with completely different levels of contrast and white balance which became a total red flag on my end that needed addressing and I'd have to adjust the scan to reflect some sort of printing density variant based off an averaged Status M reading.

So knowing that your SpecTD units can measure between "RP180 & Academy© Printing density (APD)", which are two separate scalings, it becomes a conundrum as to which measurement scaling is considered the baseline to your PFEs.

No, you are missing the point.
All scanner/telecines should be calibrated to output the same image from the same piece of film.
If they do not, they are just not calibrated.
Whichever print density is in use, the calibration should generate the same output log image.
But, APD is likely the most common in use.

Steve

Steve
Yeah, in theory the scanner should output the same image, and the correct one at that rather than something that doesn't even remotely reflect the density of the stock involved, but unfortunately that's out of my hands and it's all just damage control at this point.

Anyways, thank you for the answer and best wishes.

If you get the film transfer company to scan a calibration strip in the same stock it would be simple to generate a LUT to correct the scanner output, after the scans have been done.

Steve

Steve
Thanks for the advice. Unfortunately, my line of work involves primarily working with early–70s era negatives, hence my fixation on Status M stock readings to reverse engineer a ballpark printing density to adjust the given scan to.

It's an annoying compounding issue where I know both fading / other photochemical aging issues could result in the alterations in color and contrast, whilst simultaneously knowing there is indeed a problem with the scanners / scanner operators I have to commission from when I'm given re–scans of reels that have completely different levels.

If I do ever end in a project though that involves newer stocks that don't pre–date the late–90s, I would probably try and pursue a calibration strip for it—if available.

You really cannot use printing density to reverse engineer a scanners output, as you have no idea how the scanner was calibrated...
But, knowing how the scanner transfers ANY calibration film will get you far closer to being able to correct the output.
Film density is basically film density for any stock.

Steve