Process · Screen printing
Screen printing color separation, measured, not guessed.
Positive halftone film, spot-color separations (Sanguine) or halftoned CMYK, registration marks. Then measure your own dot gain — insolation and ink spread through the mesh, not a chart average.
Article vérifié par Tristan Sidem + Raphaël Lebas de Lacour
Le problème
Sound familiar?
- 01
Highlights disappear at exposure
Small halftone dots that were supposed to hold the lightest tones do not harden the emulsion enough — they wash out at rinsing, and the print comes out with no highlights at all.
- 02
Midtones plug up on the print
Ink spreads through the mesh beyond the open dot. A 50% dot on the film can cover 65-75% on the shirt or the paper — differently in every workshop, since it depends on your mesh, ink and pressure.
- 03
Moiré between colours in a halftoned job
Every film comes out at the same screen angle. Overlay two or three halftoned separations and an interference pattern can appear where traditional prepress would have rotated each angle.
La différence sur un tirage Screen printing
Le même fichier source, tiré sans calibration à gauche, calibré avec Calibration Flow à droite. Tu vois directement comment la calibration libère la plage tonale complète de ton procédé Screen printing.
Spécificités du procédé
A positive film, a mesh that sets the ceiling, and ink that spreads.
Screen printing is not an alternative photo process — it is frame printing: a silk (or polyester) mesh screen, coated with a photosensitive emulsion, exposed under a film, then rinsed and squeegeed with ink. That changes the first rule you have to unlearn coming from cyanotype or Van Dyke: the film is a positive, not a negative. The emulsion hardens where light passes; the film must be opaque wherever you want ink.
A screen only knows two states — ink passes, or it does not — so tonal gradation has to become dots of variable size: a classic AM halftone, angled screen, with an automatic Floyd-Steinberg error-diffusion fallback when the configuration suits it poorly. Frequency follows export resolution (300 dpi ≈ 50 lpi, 400 ≈ 67, 500 ≈ 83) and must respect the mesh: lpi ≤ threads per inch ÷ 4-5. Fine paper/poster meshes (≥ 90 threads/cm) are comfortable at 50 lpi; coarse textile meshes (43-55 threads/cm) push you towards flat spot colours or error diffusion instead.
Multi-colour separation has two regimes. Sanguine splits the tonal range into 2-3 spot films by band, with a reconstitution check and a share slider — the most common setup in craft screen printing. Halftoned CMYK goes up to 4 films (7 inks in Full Gamut), but every film shares the same screen angle: a real moiré risk in a halftoned quadri job that traditional prepress avoids by rotating each angle, which this tool does not do. Registration uses mini-Venn marks.
What calibration actually fixes is dot gain: the tonal drift from exposure and ink spread through the mesh, specific to your mesh + emulsion + ink + squeegee pressure. Print a 25-patch target under your real conditions, photograph it, and the measured curve compensates it — recalibrate at every change of mesh, ink, emulsion or press. It does not fix mechanical defects: an unevenly tensioned screen or uneven exposure still needs a stable process before you calibrate on top of it.
Target polarity: positive — the one process on this site where that is true.
Lire en détail dans le manuel
Référence externe : Wikipedia
Génère ta mire Screen printing maintenant
Mire 25 patchs (grille 5×5 + dégradé continu), paliers d'environ 4.2 % d'intensité, échelle L* CIELAB. Polarité positive (correspond à ce procédé). Télécharge, imprime sur transparent jet d'encre sans gestion de couleur, insole sur ton papier sensibilisé.
Version téléchargée en 1680×1410 px, adaptée à un tirage standard. Pour des dimensions et un nombre de patchs personnalisés, utilise la fonction mire sur mesure de l'app, débloquée avec le code Luminograph.
Mire générée par le même algorithme que l'app (fonction generateSingleMire). Échelle de mesure : luminance perceptuelle L* CIELAB.
Workflow en 3 étapes
Mire, insolation, courbe.
Generate the halftoned positive film (or separations)
Positive mode, Dither halftone on (AM screen, error-diffusion fallback if needed). Sanguine for 2-3 spot inks, CMYK for a halftoned quadri job.
Expose the screen, print the 25-patch target
Coat the emulsion, expose, rinse, dry. Print the target under your real conditions: your mesh, your ink, your squeegee pressure, your substrate.
Photograph, measure, export the .acv curve
The app reads the real value of each patch and builds the dot-gain compensation curve, applied to every film you export afterwards.
Ajuste la courbe en direct
Calibration Flow corrige n'importe quelle réponse non-linéaire avec trois sliders. Pas de point à dessiner à la souris, pas de Bézier à manipuler. Joue avec les valeurs ci-dessous et vois immédiatement l'effet sur la courbe et sur le rendu tonal Screen printing.
Entrée 0–255 ↔ Sortie 0–255
Seuil d'entrée minimum. Tout ce qui est en dessous devient noir pur.
Seuil d'entrée maximum. Tout ce qui est au-dessus devient blanc pur.
Courbure des tons moyens. 1,00 = linéaire, < 1 = mid-tones sombres, > 1 = mid-tones clairs.
Dégradé source (avant correction)
Dégradé corrigé (après application de la courbe)
Cette démo applique une formule simple (points noir/blanc + exposant gamma) pour l'illustration. L'app utilise en plus un lissage par LOWESS robuste + PCHIP monotone qui arrondit les transitions sans créer d'artefacts. Tu exportes ensuite un fichier .acv chargeable dans Photoshop ou Affinity Photo en deux clics.
Preuve d'autorité
Pourquoi nous faire confiance.
« Screen printing is the process that reverses the rule every alt-process photographer learns first: the film is positive, not negative. Beyond that inversion, the real work is the same — measure what your own screen, ink and squeegee actually do to a tonal step, and correct exactly that. Not a chart average, your own dot gain. »
Références techniques
- Wikipedia — Screen printing (mesh, emulsion, squeegee mechanics)
- Wikipedia — Dot gain (halftone dot growth at exposure and printing)
- Calibration Flow manual — Making a screen printing halftone film, Halftone frequency and screen mesh, Calibrating dot gain
Signé
- Tristan Sidem — founder of Calibration Flow + Vision Picturale
- Raphaël Lebas de Lacour — co-founder of Vision Picturale
Accès & tarif
Essayer Calibration Flow.
Web
Free with account
- 3 curves, unlimited presets, 10 HD scans, 300 MB storage
- No credit card required
iOS
€9.90/month
- HD Full Gamut export (5-7 inks)
- Advanced settings, CMYK tonal separation, reference curves
- iPhone capture, cross-device sync via the Web app
Code Luminograph
1 year of Pro included
- Shipped with the purchase of a Luminograph at Vision Picturale
- One year of Pro mode, then reverts to free
- Extended quotas and 5 GB of cloud storage
Comparatif honnête
Calibration Flow face aux alternatives.
| Dimension | Calibration Flow | QuadToneRIP | PiezoDN | Méthode manuelle |
|---|---|---|---|---|
| Dot gain calibrated by measurement | 25-patch target, photographed | Not applicable (film RIP) | Not applicable (film RIP) | Estimated by eye, table by table |
| Positive halftone film output | Native, in-browser | Not applicable | Not applicable | Manual, in Photoshop |
| Screen-angle rotation (anti-moiré CMYK) | — | Not applicable | Not applicable | Yes, traditional prepress |
| Entry price | €0 (free) | Not applicable | Not applicable | $400-900 (dedicated separation software) |
| Mobile capture | ✓ | — | — | — |
Quand choisir un autre outil
A dedicated screen-printing RIP (separation software in the $400-900 range) still wins on traditional per-colour screen-angle rotation for a large halftoned CMYK production run. Calibration Flow stays relevant for the step none of them do: measuring your actual dot gain from a photographed target instead of assuming a standard curve — and it costs nothing to try.
FAQ
Questions from screen printers.
- Positive, always. That is the opposite of contact-exposure photo processes (cyanotype, Van Dyke, platinum/palladium), which need a negative target. In screen printing, the photosensitive emulsion hardens where light passes through, so the film must be opaque wherever you want ink. In Calibration Flow, pick Positive mode (Type tab) — the rest of the workflow (halftone, registration, calibration) does not change.
- The workshop rule: lpi ≤ threads per inch ÷ 4 to 5. In Calibration Flow, the halftone frequency follows export resolution — 300 dpi ≈ 50 lpi, 400 dpi ≈ 67 lpi, 500 dpi ≈ 83 lpi. A fine mesh (≥ 90 threads/cm, paper or poster work) is comfortable at 300 dpi. A coarse textile mesh (43 to 55 threads/cm) makes a 50 lpi AM halftone risky — prefer flat spot colours (Sanguine) or test the error-diffusion fallback on a strip before a run.
- That is what Sanguine does: it splits the tonal range into 2 or 3 spot films, one per band, each with its own exposure rank and a reconstitution check that verifies the overlay rebuilds the image before export. The share slider sets your tolerance to registration drift. It is the most common setup in craft screen printing — and it avoids the moiré risk of a halftoned CMYK job, since each ink carries a different tonal band rather than the same overlaid screen.
- Yes, up to 4 films (and 7 inks in Full Gamut), with an honest caveat: every film comes out at the same screen angle, which can produce moiré between colours in a halftoned quadri job — traditional screen-printing prepress rotates each film's angle to avoid it, which Calibration Flow does not do. Test before a production run. For 2-3 colours, Sanguine stays the safer choice.
- A halftone dot grows twice over: at exposure (small dots do not always harden cleanly) and at printing (ink spreads through the mesh). A 50% dot on the film can end up covering 65-75% on the print, and how much depends on YOUR screen, YOUR emulsion, YOUR ink and YOUR squeegee pressure — no standard value predicts it. Calibration Flow measures it: you print a 25-patch target under your real conditions, photograph it, and the app builds the compensation curve applied to every following film. Recalibrate whenever mesh, ink, emulsion or press changes — the curve compensates tonal drift, not mechanical defects (an unevenly tensioned screen, uneven exposure).
Screen printing is not an alt-process photo technique — it is frame printing.
The Picturale ecosystem's six UV-exposure processes — cyanotype, gum bichromate, carbon, bromoil, gumoil, resinotype — all print by contact exposure onto a light-sensitised surface, negative film against paper. Screen printing works the opposite way: a positive film exposes a stencil on a mesh screen, then ink is pushed through by hand with a squeegee. Calibration Flow calibrates it the same way regardless: you print a target under your real conditions, scan it, measure it, export a .acv curve.
A few references if you are starting screen printing:
- Screens and emulsion — mesh count is given in threads/cm (Europe) or threads/inch; photosensitive emulsions and diazo/photopolymer sensitisers are sold by most screen-printing suppliers (Fimor, Sun Chemical, MacDermid) with their own exposure-time charts as a starting point.
- Ink — water-based inks (textile, more environmentally benign, heat-cured) and plastisol inks (opaque, does not dry in the screen, also heat-cured) behave differently for dot gain and mesh choice; this tool does not measure or distinguish between them, only the tonal result on your print.
- Registration — mini-Venn marks help align 2-4 colours by eye; a mechanical registration jig remains the reference for production runs.
- Reading — Wikipedia's Screen printing and Dot gain entries cover the underlying mechanics referenced above.
- Calibration — open Calibration Flow, follow the step-by-step. Positive film, target print, scan, measurement,
.acvcurve — the same workflow as for a cyanotype, just a positive film and a mesh instead of a negative and paper.
Do you also practise a Vision Picturale process in parallel (cyanotype, gum bichromate, carbon…)? See the six ecosystem processes →
Measure your dot gain before your next production run.
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