darktable preset inspired by KodakDouble-X 5222

What the style changes

The style converts the photo to black and white the way Double-X sees color, then adds a medium-contrast curve and visible grain. What it is based on is detailed on the Kodak Double-X 5222 film page. All figures below compare the style with darktable’s base rendering, measured in CIELab.

• Gray from the film’s spectral sensitivity. A color calibration instance named “N&B” mixes the channels with weights computed from Kodak’s published sensitivity curve (datasheet H-1-5222, equal-energy basis, integrated against the CIE 1931 color matching functions). In our test photo, the sky gets lighter (L 55.3 → 59.8), skin is almost unchanged (78.2 → 78.0) and a pink T-shirt gets slightly darker (47.3 → 46.5).
• Medium contrast, rich blacks. The tone curve deepens the shadows and closes the highlights early. Contrast rises from 14.3 to 16.6 on one test photo and from 30.7 to 32.0 on another, less than the Tri-X style (33.5 on the same photo). The darkest 5 % of the frame drop from L 2.6 to 1.1.
• Visible grain. Grain is sized from the RMS granularity of 14, with a strength of 28 against 32 in the Tri-X style.
• A truly neutral gray. Chroma falls from 8.6 to 0.0: no color cast is left.
• Highlights not blown. Checked by eye on the four test photos; the 95th percentile stays at L 87.8 on the brightest one (87.9 before).

What it leaves alone

• Your base development. The style contains no exposure, no sigmoid or filmic and no LUT.
• 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 (“as shot in camera”, CAT16, like darktable’s default, so it can be switched back on), and the “N&B” instance, which does the conversion. Without it, an active color calibration running after the conversion would tint the gray.
• It also replaces your tone curve and grain. The style’s tone curve and grain carry no instance name, so they replace any settings you had already made in those two modules. Your earlier settings remain in the history.
• Your pipeline order. The style file carries no module order list.

Details on applying styles are in Install and apply darktable styles.

Limits

• The spectral curve was read by eye. The reading has an uncertainty of ±0.05 log, and the red cutoff near 640 nm is only estimated. The style’s weights are close to those of Tri-X, so the difference between the two styles comes mostly from the tone curve and the grain. A later trace of the same graph, shown on the film page, differs from the by-eye reading by up to 0.10 log (at 640 nm); the weights were not recomputed from it.
• Reviews disagree on contrast, and it depends on the developer. The style aims at a medium rendering, between the two.
• The film’s narrow latitude is not reproduced. Reviews cite about 1.5 stops each side; the style is applied to an image whose exposure is already corrected.
• The grain. darktable’s grain is procedural noise. The strength gap with Tri-X (28 against 32) rests only on the gap between the two datasheets’ RMS figures (14 and 17), measured in different developers.
• An interpretation, not a calibration. No film was scanned or measured to tune the style.

Tips

• Apply it early. If you plan to fine-tune the tone curve or grain, apply the style first.
• 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.