darktable preset inspired by KodakTri-X 320

What the style changes

The style converts the photo to black and white, then adds a tone curve and grain aimed at Tri-X 320. What it is based on is detailed on the Kodak Tri-X 320 film page. Figures below come from renders made at 1000 px and measured in CIELab, on four test photos. The Tri-X 400 style is the reference for comparison.

• Gray from the Tri-X 400 curve. A color calibration instance named “N&B” mixes the channels with the weights of the only spectral curve in datasheet F-4017, which is Tri-X 400’s. This is an assumption: the 320 is a different emulsion.
• Contrast a little lower than the 400 style. The tone curve has a long toe, a gentler midtone slope than the 400 style and no shoulder. Contrast rises from 14.3 to 16.2 on one test photo (the 400 style: 18.0) and from 30.7 to 32.4 on another (33.5). The darkest 5 % of the frame drop from L 2.6 to 1.1 (400 style: 0.8).
• Highlights keep rising. L95 goes from 87.9 to 89.5.
• Finer grain than the 400 style. Grain is sized from the RMS granularity of 16 (400: 17), with strength 24 instead of 32. This was judged by eye on the JPEGs and not measured.
• A truly neutral gray. Chroma falls from 8.6 to 0.0.
• Sky: L 55.3 to 59.2, lighter than the base as with any panchromatic film, and a little less than the 400 style (60.7). Sea (38.4 to 38.3) and skin (78.2 to 78.6) barely move.

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. A disabled unnamed instance replaces your main one, set to “as shot in camera” with CAT16, so chromatic adaptation cannot tint the gray. The “N&B” instance does the conversion.
• It also replaces your tone curve and grain, which carry no instance name in the style. Your earlier settings remain in the history.
• Your pipeline order. The style carries no module order list.

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

Limits

• An interpretation, not a calibration. No film was scanned or measured to tune the style.
• The spectral weights are the 400’s. Kodak publishes no curve for the 320.
• The differences from the 400 are modest. The datasheet gives a one-point grain difference and the same target contrast index. The rest comes from forum opinions that partly contradict each other: an initial assumption of a curve gentler than the 400’s, against forum descriptions of highlights that keep rising. The style is a compromise, with a gentler midtone slope and no shoulder.
• Format. Kodak sells the 320 in sheets today. Its behavior in 120 is not documented here.
• The developer. The tone curve targets a classic D-76 rendering.
• The grain. darktable’s grain is procedural noise, not the shape of silver grains.

Tips

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