darktable preset inspired by AgfaCT Precisa 100

What the style changes

The style adds four darktable modules. It follows descriptions of the original Agfa emulsion: deep blues, a slight warmth, less vivid greens, natural skin and a moderate slide-film contrast. The sources, and the doubt about which emulsion they describe, are on the Agfa CT Precisa 100 film page. All figures below come from renders measured in CIELab on four test photos.

• A modest rise in contrast. The tone curve has a slope of about 1.7, read by eye from the datasheet graph and set a little softer than the Provia style, because reviews call the film lacking in contrast. Contrast (Lsd) goes from 14.3 to 16.0 on photo 0775 and from 30.7 to 32.8 on photo 1014. The darkest 5 % of photo 1014 fall from L 2.6 to 1.4 and the brightest 5 % rise from 87.9 to 90.1.
• Deeper blues. Color equalizer raises blue and cyan saturation. Sky chroma goes from 27.5 to 32.0 (+16 %) and sea chroma from 22.2 to 27.3 (+23 %). Both hues drift 2 to 4° toward violet (sky 273.6° to 275.9°, sea 270.1° to 273.8°). That drift is larger than the Provia style’s, which stays under 1°.
• A slight warmth. A color balance rgb instance named “film” tints the midtones toward 40° and leaves blacks and whites neutral. A warm gray patch on photo 1014 moves from a/b +3.9 / −3.4 to +5.4 / −2.6.
• Natural skin, slightly warmer. Skin chroma goes from 16.4 to 18.3 (+12 %) and its hue from 44.2° to 45.9°. The midtone warmth causes most of it.
• Less vivid greens. Green saturation is ×0.93 and its hue moves −3°. This follows a single review and is not checked on the test photos.
• Fine grain. With an RMS granularity of 10 on the datasheet, the grain is set to a small size and a low strength.

No flat area or posterization appeared on the four test photos, and shadows and whites stayed open.

What it leaves alone

• Your base development. The style contains no exposure, no sigmoid or filmic, no white balance, no color calibration and no LUT: those stay as you set them.
• Your pipeline order. The style file carries no module order list, so it does not impose one on your image.
• Your own color balance rgb. The style’s instance is named “film”, so it is added next to yours without changing it (unless the photo already has an instance named “film”, for example from an earlier application of the style).

What it does not leave alone: applied from the lighttable or the darkroom, each module of the style replaces the instance of the same name on the photo, or is added if there is none. The style’s unnamed modules, color equalizer, tone curve and grain, therefore overwrite any settings you had already made in those modules. Your earlier settings stay in the history stack. Exporting with a style, or rendering with darktable-cli as our measurements do, adds the style’s modules as separate instances instead. Details in Install and apply darktable styles.

Limits

• An interpretation, not a calibration. Few sources exist and they disagree on contrast and warmth. No film was scanned or measured to tune the style.
• Two films under one name. Some sources say the last AgfaPhoto CT Precisa was Fujifilm Provia 100F repackaged, and closer to that film. The style follows the description of the original Agfa emulsion.
• A range brochure, not a dedicated datasheet. The 2007 AgfaPhoto brochure gives no D-min or D-max in numbers, so the curve is read by eye from its graph.
• Cross processing is not simulated. It is the main use Kosmo Foto cites for the original film.
• The greens rely on a single review and cannot be checked on the test photos, which hold few of them.
• The grain is set from the RMS 10 figure, with no side-by-side measurement.
• The measurements come from a few test photos of our own. They are not published on this site.

Tips

• For a more neutral slide look, set the midtone chroma of the “film” color balance rgb instance to 0, or lower its midtone warmth.
• For bluer skies, raise the blue saturation in color equalizer above ×1.10. The sky hue already drifts toward violet, so go step by step.
• Installation: see Install and apply darktable styles.