A test chart is a pattern printed then exposed like a negative — or measured directly —, calibrated to characterize a process's response on a given paper. It's the object the whole chain is built on: if the chart is right, the curve will be right. If it's printed approximately, the curve corrects against nothing.
In Calibration Flow, the chart doesn't live in a screen of its own: it's drawn directly on your negative. Open the Negative screen, import your image, then in the options bar at the bottom — Format · Style · Effects · Target — open the Target tab and turn on "Show the target". Calibration Flow adds a 25-step grey scale at the bottom left of your image, from white to black, with a continuous gradient in the 6th column. It's free, no Pro Mode restriction.
The chart follows the generation mode you picked for your print — Negative or Positive — just like the rest of the image: there's no separate polarity setting for it. The rule: negative chart for most Vision Picturale processes (cyanotype, Aquaprint, bromoil, carbon, gumoil), positive for resinotype and screen printing. See Positive vs negative chart for the detail per process.
Absolute rule, which ruins the calibration if you forget it: print your negative with no color management at all. See Printing a test chart without color management for how.
#Raw chart or control chart
Calibration Flow draws the chart before applying the curve and the inversion: it gets exactly the same transformation as your image. As long as you don't have a custom curve yet, the curve selector stays on "Standard curve" — the default option, which applies no correction — and your chart comes out raw: that's the one for a first calibration. Once a calibration curve is selected, the same chart becomes a control chart: a glance is enough to see whether that curve still holds on this paper, this chemistry or this exposure.
#Multi-zone mode
To compare several curves on a single print, the same Target tab offers Multi-zone mode (1, 2 or 4 zones): Calibration Flow splits your image into zones and puts its own small 5×5 chart with gradient on each one; each zone gets the curve you assign it, and a label carrying that curve's name. Handy for settling between two close curves on a single sheet of paper instead of two separate exposures.
Worth knowing: turning on "Show the target" automatically switches off "Fill the paper" — the two are incompatible, your image keeps its proportions to leave room for the chart.
#A standalone chart, without printing it with your image
In the app, the chart prints directly on your negative — there's no separate "chart only" file to download. If you want a standalone file (to test your printer alone, for example), the site offers several free generators, no sign-up needed: the 21-step target (PNG at 300 dpi, polarity of your choice, no watermark), or the 25-patch chart built into process pages like cyanotype calibration — the same calculation as the app's own chart. The one on the screen printing calibration page can be screened, up to 600 dpi.
#What you'll find here
- Types of test chart — the inventory of the charts Calibration Flow actually offers today, process by process.
- Positive vs negative chart — the rule: negative for most VP processes, positive for resinotype and screen printing.
- Test chart with gradient — the continuous gradient that comes with the monochrome chart, and what it's for.
- A4 300 dpi test chart — the chart's resolution: your negative's in the app (300, 450 or 600 dpi), 300 dpi for the site's files.
- Create a custom test chart — what you can actually adjust (Multi-zone, the site's generators), and what can't be adjusted anywhere.
- Printing a test chart without color management — the golden rule, to read before anything else.
#Getting started
You're making your first cyanotype. The monochrome chart in negative polarity is what applies. Turn it on from the Negative screen: Target tab → "Show the target". Read Printing without color management first so you don't get caught out on your very first print, then go to Getting started → First calibration for the rest.
You're making an Aquaprint gum print or a carbon print. Same monochrome chart, in negative. See A4 300 dpi test chart for the resolution and dithering setting that matters for these pigment-based chemistries.
You're making a screen print or a resinotype. These are the only two cases that call for the monochrome chart in positive polarity. See Positive vs negative chart for why.
You're calibrating the printer itself. Same monochrome chart, in negative — Calibration Flow doesn't treat printer calibration any differently from an alternative process.
You're preparing a color Aquaprint with Color Venn. The Color Venn tool is what applies here, not the monochrome chart: it checks how your inks overlap before you run a full four-colour print. See Color Venn.
#What's next
Once your chart is printed and exposed like a normal negative, scan it: Calibration Flow reads the L* value of each patch and generates your calibration curve. The Free tier (sign up, no card, 3 curves) is enough to calibrate your first process — see Calibration Flow pricing to compare tiers.