This discussion focuses on the importance of the 3×3 transformation matrix used to convert Plog-encoded film scans into a linear color space. Accurate color space conversion is essential for consistent and reliable post-processing of scanned film negatives. The transformation is achieved through a DCTL (DaVinci Color Transform Language) script, which is publicly accessible at https://github.com/Demystify-Color/DCTLs/blob/main/Technical%20Transforms/DMC_PLogLin.dctl. This tool enables users to place their film scans within the correct color space, thereby facilitating the creation of scene-referred looks, as previously outlined in the initial installment of this series.
The DCTL operates by converting the logarithmically encoded scanned images into a linear color space representation. This linearization is a crucial step before applying a Color Space Transform (CST) to translate the footage into the desired target color space. It is imperative that the target footage shares an identical color space configuration to ensure visual consistency and accurate profiling.
Brightness adjustment within the DCTL is managed by manipulating the “LOG Reference” slider. The procedure involves initially applying a blur filter to the scanned image to minimize noise and local variations. Subsequently, middle gray values are measured using an RGB picker tool, and an average value is calculated. This average is then input into the DCTL parameters, effectively aligning the brightness levels between the source scan and the target footage. This alignment ensures a more precise match in terms of luminance, thereby enhancing the fidelity of subsequent color transformations and profiling process.
Using an Output Device Transform (ODT) at the end allows verification that all applied transforms function correctly and do not introduce unwanted artifacts.
Demystify Color. “Film Profile Journey 11: A Better Way to Prep Your Negative Scans.” Demystify Color, June 2024. https://www.demystify-color.com/post/film-profile-journey-11-a-better-way-to-prep-your-negative-scans.
