A test chart is a grid of grey patches ordered from pure white to the deepest black, calibrated mathematically. It's the object the whole chain is built on. If the chart is right, the curve will be right. If the chart is printed approximately, the curve will correct against nothing.
Calibration Flow supplies six ready-to-print test charts. Three in negative polarity (cyanotype, Aquaprint, bromoil, carbon, gumoil — most Vision Picturale processes, plus printer calibration) and three in positive polarity (positive interpositive, used for resinotype). For anyone who needs a chart at unusual dimensions, custom chart creation is announced as an advanced feature unlocked by the Luminograph code — it is currently being integrated.
The Test Chart module isn't a long module. The technique comes down to three rules: the right polarity for your process, the right variant (plain flats or bitmap dithering) for your chemistry, and — the absolute rule — no color management when printing the transparency. A whole page is devoted to that last one, because it's the number-one cause of calibrations that don't work.
#What you'll find here
- Types of test chart — the inventory of the six supplied charts, with a table that tells you which one to choose for your process.
- Positive vs negative chart — the simple rule: every VP process in negative, except resinotype in positive (positive interpositive).
- Test chart with gradient — what the continuous gradient adds to the chart of discrete patches, and when it really helps.
- A4 300 dpi test chart with dithering — the bitmap chart, especially useful for carbon and Aquaprint, but usable on any process whose printer doesn't render flats well.
- Create a custom test chart — the tool to generate a chart at your exact dimensions (announced advanced feature, unlocked by the Luminograph code — currently being integrated).
- Printing a test chart without color management — the golden rule, to read before anything else.
#Getting started
You're making your first cyanotype. Download the plain A4 negative chart (chart 1), read Printing without color management, print it on an inkjet transparency, then go to Get started → First calibration.
You're making a carbon or an Aquaprint (gum print). Download the A4 300 dpi bitmap negative chart (chart 3). The bitmap renders tonal transitions better on these pigment-based chemistries — it's especially useful on those processes, but the bitmap chart isn't reserved exclusively for them. See A4 300 dpi test chart with dithering for the rationale.
You're making a resinotype. Download the plain A4 positive chart (chart 4). Resinotype is the only VP process that calls for a positive interpositive. See Positive vs negative chart for why.
You're calibrating the printer itself. Calibration Flow is also used to compensate for your printer's non-linear response, independently of any alt-process. Take the plain A4 negative chart (chart 1), print it, scan it, generate the curve. The curve gives you the pre-processing to apply to all your future prints before output.
Your process doesn't use A4, or you want custom patches. The create a custom test chart tool is announced to generate a chart at your chosen dimensions and patch count. It's an advanced feature unlocked by the Luminograph code (shipped with the purchase of a Luminograph from Vision Picturale). Distinct from the iOS Pro subscription. This feature is currently being integrated — the six supplied charts cover most uses in the meantime.