darktable preset inspired by FomaFomapan 200 Creative

What the style changes

The style converts the photo to black and white the way Fomapan 200 sees color, then adds its soft contrast, lifted shadows and visible grain. What it is based on is detailed on the Fomapan 200 Creative film page. All figures below come from renders made with tools/validate.py at 1000 px, measured in CIELab, and compare the style with the base render.

• Gray from the film’s spectral sensitivity. A color calibration instance named “N&B” mixes the channels with weights computed from Foma’s published spectrogram. The curve is integrated against the CIE 1931 color matching functions, after dividing out the 2850 K tungsten light it was measured under: this is how darktable builds its own film presets, such as “monochrome | ILFORD HP5+”.
  • On the test photos, the sky gets lighter (L 55.3 → 59.3) and skin darker (78.2 → 75.5), with the tone curve and grain included in these figures.
  • The blue weight (0.415) is higher than for the Fomapan 100 style (0.403).
• Soft contrast. Global contrast barely moves: Lsd goes from 14.3 to 15.0 on one photo and from 30.7 to 30.2 on another. The Fomapan 100 style, made with the same photos, raises the second one to 34.0, so the 200 is much softer.
• Blacks that stay open. The darkest 5 % of the frame go from L 2.6 to 2.2 (0.3 with the Fomapan 100 style). The brightest 5 % are held back slightly, from L 87.9 to 86.0, because the curve stops at 0.985.
• Visible grain. Grain is sized from the RMS granularity of 14.0. Its strength (27) sits between the Fomapan 100 style (24) and the Tri-X 400 style (32).
• A truly neutral gray. Chroma falls from 8.6 to 0.0: no color cast is left.

What it leaves alone

• Your base development. The style contains no exposure, no sigmoid or filmic and no LUT. Those settings stay as you made them.

• But it switches off your main color calibration. The style contains two color calibration instances:

  • a disabled one with no instance name, which replaces your main color calibration and switches it off. It is set to “as shot in camera” with CAT16, like darktable’s default, so you can switch it back on;
  • the “N&B” instance, which is added and does the black-and-white conversion.

  Why: when an active color calibration runs after the black-and-white conversion, its chromatic adaptation tints the gray. darktable’s built-in black-and-white presets also bypass chromatic adaptation, and film does not white-balance either.

• It also replaces your tone curve and grain. When you apply a style from the lighttable or the darkroom, each of its modules replaces the instance of the same module with the same name, if the photo has one, and is added otherwise. The style’s tone curve and grain carry no instance name, so they replace any settings you had already made in those modules. Your earlier settings remain in the history.

• Your pipeline order. The style file carries no module order list, so it does not impose one on your image.

Exporting with a style, or rendering with darktable-cli, works differently: every module of the style is added as a separate instance, and the disabled color calibration still switches off the existing one. The details are in Install and apply darktable styles.

Limits

• An unscaled chart. Foma’s spectrogram has no graduation on its sensitivity axis. We assumed the curve spans about one log unit between the axis and the maximum, as for the Fomapan 100. With 0.8 to 1.3 log units, the X weight would move between 0.28 and 0.31.
• A reading of the image, then a finer trace. The weights were computed from a reading of the graph in a 400 dpi raster, uncertain by a few nanometers, and more so on the red cut-off (690 to 715 nm).
• Contrast: little data. The datasheet gives no slope, and its characteristic-curve graph shows only three development times, with no gamma for each. The setting follows the reviews (soft, balanced), without a measurement. Reviews are not unanimous: one describes “quite contrasty” negatives.
• The grain. Reviews disagree, and it depends on the developer. The setting is an average value. darktable’s grain is procedural noise: it imitates the texture of film grain, not the shape of real silver grains.
• No halation. The datasheet lists no anti-halation backing for 35 mm, and we found no source on its size for this film, so the style does not simulate it.

Tips

• Apply it early. If you plan to fine-tune the tone curve or grain yourself, apply the style first: it would replace those settings if you made them before.
• See the spectral conversion alone by switching off the tone curve and grain modules the style set.
• More punch: raise the tone curve’s midtone slope, or apply the Fomapan 100 style for a harder look.
• Back to color: switch the main color calibration back on and switch off the “N&B” instance.
• Installation: see Install and apply darktable styles.