I am teaching an ACES workflow at a film school that has an Cintel film scanner. I never operate the scanner myself, but I’m trying to figure out how in theory one might set the Cintel up to scan to ADX10/16 for an ACES workflow so that I can relay the information to interested students as well as those who do operate the scanner. Does anyone have experience with this?
I have found the ACES Technical Bulletin 2014-005 which seems like it may have the relevant information in terms of technical transformations that need to be implemented, but I could use some guidance on how it might translate into a practical workflow to figure out whether it might be feasible for my school.
In my experience with this scanner, I have found that a majority of the scans done with default settings into a DaVinci YRGB project already look ‘good’, or as close to correct as I can tell, when interpreted with an ADX10 IDT in an ACES project. However, I have encountered a few scans of underexposed negatives that appear to have crushed or compressed blacks that can be recovered if interpreted using certain methods (i.e. using an ADX16 IDT and dropping the gain, which was a method suggested elsewhere on these forums), but also point to the probability that the Cintel is not properly set up for ADX encoding. However, if that’s the case, then I am curious why the ADX10 IDT does seem to ‘work’ much of the time without any adjustment to scanner settings.
Guidance from anyone who is familiar with an ADX workflow or has experience setting up a scanner, especially a Cintel, for ADX encoding would be greatly appreciated!
ADX code as implemented has a clip for values below “DMIN” circa 95CV
But maybe you have not run into that specific problem.
Setup of a scanner can be quite a complex topic, typically you want the scanner to be able to detect the 3 records of different film stocks and then calibrate the output to give you the printing density.
The printing density is akin to what a ‘print sees’ when being made in a printer, i.e. it is a function of the printer’s lamp source, colour filters (including the base colour of the negative) and the print’s own spectral sensitivities.
As you say the scanner you have probably is not setup to correctly capture APD values but hopefully some other similar density type of metric, maybe even Status M. Under those conditions a linear 3x3 transform +/- an offset term can get you close enough.
If you wanted to tune this process you would want to optically expose your chosen negative film stock with a suitable range of colours to generate a set of negative densities for you to scan. You would want to spectrally measure the densities and use them using the procedure outlines in the document to compute your reference APD target values for that film stock.
You then scan the film on the scanner with nominal unity settings and measure the resulting code values. Comparing these with your calculated targets you can then compute adjustments for your scanner’s calibration mechanisms, typically on scanners I have done this for they have a 3x3 matrix which can be applied on the log encoded data.
There can be a number of nuances in generating and measure the coloured patches as well as how you compute your calibration matrix (unity gains, accounting for DMIN fluctuation, etc). These often come out of the fact that the assumption that a linear matrix is sufficient, may not hold, this is also suggested by the document.