Processes · Map
The alternative processes calibratable with Calibration Flow.
Six processes covered in detail, three tangent processes documented in the manual. Each process has its own constraints: Dmax, target polarity, number of passes, chemistry cost. This page helps you find yours before committing the paper.
Article reviewed by Tristan Sidem + Raphaël Lebas de Lacour
Five processes, five tonal signatures
Every alt-process renders the tonal range differently: cyanotype leans to Prussian blue, Van Dyke to purple-brown, platinum to a neutral grey, carbon to a deep composite black. Here is each signature, from paper white at the top to maximum pigment at the bottom. Click through to the calibration page of the process you have in mind.
Cyanotype
Prussian blue
Dmax ~1.4
Gum bichromate
Free pigments
Variable
Platinum/palladium
Neutral grey-black
Dmax ~1.8
Van Dyke
Purple-brown
Dmax ~1.5-1.7
Carbon
Deep CMY black
Dmax > 2.1
Les dégradés ci-dessus sont des simulations synthétiques de la signature de chaque procédé sur papier coton — un vrai tirage dépend du papier précis, de la chimie, de la source UV. Ces palettes te donnent l'allure générale ; ta calibration personnelle te donnera la vraie courbe.
01 · The six processes covered in detail
One landing page per process, with FAQ, workflow, honest comparison.
Process · Prussian blue
Cyanotype
The entry process into alt-process. Ferricyanide + ferric citrate, simple sensitisation, 24 h oxidation after exposure. Typical Dmax 1.4 on Arches 300 g. Negative target polarity.
Process · CMYK multi-pass
Gum bichromate (Aquaprint)
Pre-sensitised gum arabic + dichromate-free Universal Sensitiser + pigments. Multi-layer, up to 4 separate negatives in quadricolour, critical registration. The most tonally free process, but the most demanding to calibrate.
02 · Three tangent processes
No dedicated preset — and they calibrate anyway.
Calibration Flow offers no dedicated preset for these three. Since it measures a result rather than a method, the 25-patch target still works — the manual route is on one page. The processes themselves, their chemistry and their kits, are documented by Vision Picturale.
Bromoil
Brush inking of gelatin on a bleached silver matrix. No dedicated preset in the app: final density comes from the inking, not from the exposure. The manual method still holds — target, print, L* reading, curve.
Calibrate it without a preset →
The process itself — Vision Picturale →04 · Common core
What every process shares inside Calibration Flow.
Whatever your process, the software chain is the same: 25-patch target (5 × 5 grid, steps of about 4 % between neighbouring patches), density reading in perceptual L* CIELAB luminance, generation of an Adobe `.acv` curve (up to 16 points, version 1, file under 1 kB). This curve imports directly into Photoshop, Affinity Photo, and indirectly into Lightroom and GIMP.
The algorithm applied to your measurement combines linear interpolation, robust LOWESS smoothing, and monotonic PCHIP interpolation — no cubic polynomial, no naive spline that would produce oscillations. Luminance is measured on 512 bins in perceptual L*, identical from one process to another. What changes by process: the target polarity, the Dmax target, and the dithering parameters applied to the final negative.
Read the step-by-step of the first calibration in the manual →
05 · Ecosystem
Calibration Flow does not sell chemistry.
CF is the software. For chemistry, the Luminograph, papers and long-form courses, you go through the other poles of the Picturale ecosystem: Vision Picturale (chemistry kits + Luminograph), Maison Picturale (recommended papers), NOEME (long-form courses). The process pages link to the right resource without duplicating it here.
Choose your process. Calibrate before committing the paper.
Free with registration on the Web version, all Pro features unlocked, no credit card required.
03 · How to choose
Which process for which practitioner?
You are starting alt-process and want a first stable print in under two weeks. Choose cyanotype. Inexpensive chemistry, only two baths, a 24 h oxidation that gives you time to judge. It is the process most practitioners recommend as a gateway, and the one Calibration Flow calibrates fastest (negative target, `.acv` curve exportable in fifteen minutes).
You want warm brown with a silver grain. Van Dyke. Ferric citrate + silver nitrate, tones that vary with the toner applied after fixing. Calibrate in two stages: base curve, then a second curve after toning if you tone systematically in gold or selenium.
You want the widest possible tonal range and accept the cost. Platinum/palladium. 300+ usable levels, museum permanence, Dmax 1.8 on Hahnemühle Platinum Rag. Calibrating before committing the platinum is not an option.
You want total chromatic freedom. Gum bichromate (Aquaprint in quadricolour). Four separate negatives, Y → C → M → K order, critical registration. It is the most tonally free process but also the longest to calibrate correctly.
You want deep blacks and a bas-relief effect. Carbon. Dmax above 2.1, pure CMY tricolour (no separate black channel). A process demanding in both chemistry and registration, but which produces the densest blacks in alternative printing.