To create the presets, a picture is taken with a film camera, then the same picture is taken on a digital camera. Both cameras are set to the same shutter speed and f-stop. The same lens is used on both cameras and the iso of the digital camera is matched to the speed of the film. Multiple pictures of different scenes and lighting conditions are taken on both cameras.
When the film has been developed, it is then scanned on a Noritsu HS-1800. (The one exception is for the color positive film, which is scanned on an Hasselblad Imacon drum scanner.) The Noritsu is one of the most popular scanners used in film labs today. While there are many different ways to scan film, the most common way was chosen to keep the look of the FiF film emulations consistent.
After the scanning is complete, the digital images and film scans are brought into lightroom. For the film images, the only tweaks that are made are to general exposure. The need for exposure compensation is caused by small variables like lens adapters, shutter speed calibration, and changing light position. Once the general exposure has been matched. The work on the digital photo begins.
Careful and meticulous adjusting of the RGB curves, HSL sliders, point color controls, color grading wheels, and grain levels are performed on the digital image to match it as close as possible to its film counterpart. This process is performed on all of the other digits/film sets as well. The tweaks between each set are slightly different, which it why there are 7 different preset styles for each individual film stock emulation.
After completing the adjustments, the presets are tested on a variety of different images taken on different cameras to insure that these presets look natural in all different scenarios.
If you follow these steps above, you can create your own presets too, but what you're paying for if you choose to get the FiF presets is amount of time and knowledge it took to develop presets that accurately emulate the look of specific film stocks.