spectral_film_lut 0.4.2

GUI to create LUTs to emulate film from spectral datasheets.

Spectral Film LUT

Spectral Film LUT is a GUI application made to generate LUT files for film emulation in video editing. For more details take a look at the documentation.

To emulate the look of a film stock, its datasheet was digitized and a multistep color pipeline simulates its reaction to light to the final appearance of the print material.

• A wide variety of negative, print, and slide materials are available.
• Options include still photography, motion picture, color, black and white, Kodak, Fuji, contemporary, and vintage.
• The accuracy is limited by the precision of the published data, which can be especially poor for long discontinued formats. There is also undocumented behavior like interlayer effects, for which simplified assumptions have been made.
• There is especially little data available about the interlayer interaction, e.g., how aggressive the color masking couplers in a negative film are.

Installation

Windows

Download the latest .exe from the releases page and run it.

Alternatively, install via Python (see below).

Linux

Download the .AppImage from the releases page and make it executable:

chmod +x spectral_film_lut-{version}.AppImage
./spectral_film_lut.AppImage

Alternatively, install via Python (see below).

macOS

There is currently no native binary available for macOS. Install and run the application using a Python-based method. See the Python Package section below.

Python Package

Install the application using your preferred Python package manager. We show it for the default pip. Others can be found in the full documentation.

pip install git+https://github.com/JanLohse/spectral_film_lut

Then just run with:

spectral_film_lut

CUDA support

For hardware acceleration we make use of CuPy. It might be removed in future releases though. There is not a relevant speed-up for generating LUTs, that justifies the added complexity in code.

Once CUDA support is removed, a legacy CUDA branch will be added. To use CUDA pull that branch and install using pip, and additionally install the https://cupy.dev/ package. To disable CUDA on an installation with CUDA capabilities, use the argument --no-cuda.

Usage

1. Select a sample image which is in the intended input colorspace.
2. Adjust the preview with the parameters on the sidebar.
3. Once satisfied, export the LUT.

• Hovering over a setting should explain what it does, and double clicking the label resets to the default value.
• When simulating slide film, set the print stock to None or an appropriate reversal print medium.
• You can also export the LUT in a negative and print stage. In your image processing pipeline this gives you the option to add grain to the negative, and use printer lights controls.

Resolve Node Tree

If you want to use the Grain LUT, the following node tree is recommended. It is important to set the correct offset of -43, so that the grain does not alter overall brightness. Import the grain overlay as a matte from the media pool tab.

It is important that all LUTs where exported with the same ADX d-max setting, and that the grain and print LUTs where made for that specific negative film stock. The grain overlay is generated independent of film stock selection, and only affected by the simulated frame size.

To manually alter the grain intensity, change the gain on the unlabeled node between the multiplicative and the additive layer mixers. Printer light controlls should be done after the additive mixer and before the print LUT. Halation should be added before the negative LUT.

Filmstock Selector

When clicking on the magnifying glass a window opens to search and browse through the available film stocks.