The rule fits in one sentence: every Vision Picturale process calls for a negative chart, except resinotype which calls for a positive interpositive. This page documents the rule, its physical origin, and the full table by process.
To calibrate a digital printer itself (compensating for its non-linear response): negative chart, just like for the standard negative processes.
#Comparison table
| Process | Chart polarity | Why |
|---|---|---|
| Cyanotype | Negative | Standard convention of contact-exposure alt-processes |
| Aquaprint Monochrome | Negative | Same — gum bichromate |
| Aquaprint Sanguine | Negative | Same |
| Aquaprint CMYK Four-Color | Negative | Same (one negative per channel) |
| Bromoil | Negative | Same — gelatin matrix VP N°05 |
| Carbon Musée Black (monochrome) | Negative | Same |
| Carbon Couleur Profonde (CMY three-color) | Negative | Same (one negative per C, M, Y channel) |
| Gumoil | Negative | Same |
| Resinotype | Positive (positive interpositive) | Exception: pigments settle on the black areas of the negative (the non-exposed areas) |
| Printer calibration | Negative | The printer is treated as a tonal chain to compensate, like a standard negative process |
#When to use a negative chart
This is the general case. Five Vision Picturale processes out of six work this way: cyanotype, Aquaprint (all variants), bromoil, carbon (all variants), gumoil. For all these processes, the source image to print on an inkjet transparency is in negative polarity — it's the standard convention of any alt-process contact print.
In Calibration Flow, choose the negative chart in the Test Chart module for these processes. It's also the default the app offers when you select one of them as the active process.
For calibrating a digital printer (Calibration Flow is also used for this purpose, independently of any alt-process): negative chart as well. The printer has its own non-linear response that Calibration Flow compensates for, handled mathematically like a standard negative process.
#When to use a positive chart (positive interpositive)
Only for resinotype. It's the only Vision Picturale process that calls for this polarity, and the app offers it as the default when the selected process is resinotype.
The reason is physical. In resinotype, the chemistry (gelatin VP N°05 + sensitizer VP N°03 + powder pigments + proprietary VP resin) behaves differently from the other hardening processes:
In an Aquaprint or a carbon, pigments stay where the UV light hardened the gum or the gelatin — that is, in the exposed areas (clear transparency = light passes = chemistry hardens). The standard negative therefore yields a positive print (because the pigments follow the logic of the negative).
In a resinotype, it's the opposite: the resin and the gelatin behave such that the pigments cling to the non-exposed areas — that is, the areas where the UV light did not reach the paper. These areas correspond to the opaque (black) parts of the negative.
For the final print to resemble the original image, you therefore have to present the chemistry with an image inverted relative to the standard convention. That's exactly what a positive interpositive is: a positive polarity (image read normally, light values staying light and dark values staying dark) used as an exposure negative.
#The trap — Aquaprint four-color vs Carbon three-color
The table above treats both color processes the same way (negative), but they differ in the number of channels:
- Aquaprint CMYK Four-Color: four separate negatives (Cyan, Magenta, Yellow, Black), each in a negative chart. Recommended print order: Y → C → M → K. Each layer is a gum layer with its own pigment.
- Carbon Couleur Profonde: three separate negatives (Cyan, Magenta, Yellow — no separate black), each in a negative chart. Pure CMY three-color. Each layer is a pigmented-gelatin transfer.
Don't confuse the two. An Aquaprint calibration generates four correction curves (one per CMYK channel). A Carbon Couleur calibration generates three curves (one per CMY channel).
For both processes, registration marks are needed to align the layers.
#Key points
| Element | Value |
|---|---|
| Chart format | 25 patches in a 5×5 grid, from pure white (patch 0) to maximum black (patch 24) |
| Negative polarity | Patches ordered white to black, read in the reverse direction of the normal image |
| Positive polarity (interpositive) | Patches ordered white to black in the normal readable direction |
| Choice in the app | You select the negative or positive chart depending on your process |
| Processes concerned | Every VP process in negative — resinotype alone in positive |
#Founder's notes
Resinotype has its polarity inverted because of a quirk of the resin + pigmented-gelatin chemistry. It's a detail that's easy to forget — hence a whole page underlining it. During Calibration Flow's first months, several practitioners reported resinotypes "coming out backwards" to us. When we dug in, it was always the same point: they'd used a negative chart like for the other processes. The "everything in negative except resinotype" rule is there so we no longer have to dig in every time.