darktable preset inspired by KodakPanatomic-X

What the style changes

The style converts the photo to black and white with weights estimated for Panatomic-X, then adds its tone curve and a very fine grain. The sources are detailed on the Kodak Panatomic-X film page. All figures below come from renders made at 1000 px with our validation tool, measured in CIELab, against darktable’s base render.

• Gray from an estimated spectral response. A color calibration instance named “N&B” mixes the channels with weights of 0.32, 0.32 and 0.36 (X, Y, Z). They come from reading the two spectrograms of the 1958 Kodak book by eye: they have no numeric scale, so this is an estimate, not an integration of a curve. Benchmarks: Plus-X (0.28, 0.24, 0.48) and Tri-X (0.31, 0.30, 0.39). With less blue weight than Plus-X, skin renders lighter (L 78.2 → 80.5).
• Contrast with a long soft toe and no shoulder. The curve follows the shape of Kodak’s D-76 curves at about 6 minutes. Contrast rises from 14.3 to 17.3 on one test photo and from 30.7 to 33.0 on another, between the Plus-X and Tri-X styles. The darkest 5 % of the frame drop from L 2.6 to 1.1, and the whites open (L95 87.9 → 90.6).
• Very fine grain. Coarseness 900 and strength 11, against 1100 and 18 for the Plus-X style. Measured on the same sky area at 2560 px, the grain is 2.1, against 3.5 for Plus-X and 6.8 for Tri-X.
• 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 (“as shot in camera”, CAT16, like darktable’s default, so you can switch it back on), and the “N&B” instance, which does the black-and-white conversion. Why: an active color calibration running after the conversion would tint the gray with its chromatic adaptation.
• It also replaces your tone curve and grain. Applied from the lighttable or the darkroom, each module of the style replaces the instance of the same name if the photo has one. The 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.

The details of applying a style are in Install and apply darktable styles.

Limits

• An interpretation, not a calibration. No film was scanned or measured to tune the style.
• Estimated spectral weights. The 1958 spectrograms are images without a scale. Weights closer to Plus-X’s, with more blue, remain plausible, and the lighter skin is a direct consequence of the estimate, not verified.
• An old book. The data date from 1958, from the reformulated “new Panatomic-X”. Later versions (1960s to 1980s, ISO 32) may have had a different curve, and most reviews describe expired film with its own effects (fog, contrast).
• No published RMS granularity for the consumer film: the grain is a choice of “extremely fine”, not a converted figure.
• The developer. The curves are for D-76 and times of 3¾ to 15 minutes; the style aims at about 6 minutes. Real contrast changes with the developer.
• The grain. darktable’s grain is procedural noise: it imitates the texture of film grain, not the shape of real silver grains.
• Compared with Pan F Plus 50. The Panatomic-X style has no local contrast and no crushed shadows: its blacks stay slightly open. Skin and sea render differently because of the spectral weights.

Tips

• Apply it early. If you plan to fine-tune the tone curve or grain, 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.
• Back to color: switch the main color calibration back on and switch off the “N&B” instance.
• Installation: see Install and apply darktable styles.