What resolution should your target have, and should it be screened? The answer comes down to one simple rule — in the app, your target has no resolution of its own, it follows your negative's; on the site, it's the opposite, each generator produces an independent file with its own settings.
#How it works
In Calibration Flow, the target that matters day to day is the Control strip: the 25-patch grid plus continuous gradient that you overlay on your negative from the generation screen — bottom option bar → Target → Show the target. This target is drawn straight into your negative's canvas: it has no dpi, format or screening of its own. It inherits everything you set for the whole sheet:
- Format (Format tab): paper size (A4 / A3+) and orientation (Landscape / Portrait).
- Resolution (Effects tab): 300, 450 or 600 dpi — the app's three real steps, the same whether or not your negative is screened.
- Screen (Effects tab): Off or On. If you print your negative with Screen on, the Control strip gets screened along with it: it's drawn before the curve and the inversion, and the screening is applied afterward on the already-composed sheet, target included.
On the site, it's the opposite: every target tool generates an independent file in your browser, with no link to a negative. The 21-step target downloads a fixed PNG — 1680 × 668 px at 300 dpi, continuous tone, polarity of your choice, no watermark and no sign-up. The process pages' 25-patch targets (including cyanotype calibration, gum bichromate, carbon, Van Dyke, platinum/palladium) are likewise fixed at 300 dpi, continuous tone. Only the screen-printing calibration page lets you pick the rendering — continuous, AM halftone or error diffusion — and, if you pick a screened rendering, the fineness too: 300, 450 or 600 dpi, with the file growing accordingly (450 dpi = ×1.5, 600 dpi = ×2 the pixels of the 300 dpi file).
#Why it matters
On your negative, raising the Resolution sharpens the edges of the target just like those of the image — useful if your process is sensitive to sharp transitions between two patches. Turning on Screen makes a dot pattern appear on the target itself: that's not a defect, it's the same sheet getting the same treatment everywhere.
On the site, continuous tone (solid patches) suits nearly every contact process — it's also what the app uses as long as you don't screen your negative. The Screen-printing page's screened rendering exists for a precise reason: a screen printer prints screened films, and measuring dot gain on a continuous-tone target would measure something other than what actually gets printed.
In the app, there's no target you can download on its own: it prints straight onto your negative. If you want a standalone target file, free and with no sign-up, the site's generators cover that need.
#When to avoid it
Don't look for a resolution setting of the target's own in the app — it doesn't exist. For a finer target, raise your whole negative's Resolution (Effects → Resolution): the target will follow automatically.
Don't turn on Screen thinking it only applies to the target: it applies to the whole sheet you generate, image included.
On the site, don't expect a resolution choice everywhere: only the Screen-printing page offers it, and only once you've picked a screened rendering. The other generators — the 21-step target as well as the process pages — deliver a fixed 300 dpi PNG.
#Technical details
| Setting | Where | Values | Default |
|---|---|---|---|
| Target's own resolution (app) | — | None, it follows the negative | — |
| Negative Resolution | Effects | 300 / 450 / 600 dpi | 300 |
| Negative Screen | Effects | Off / On | Off |
| Negative Format | Format | A4 / A3+, Landscape / Portrait | A4, Portrait |
| 21-step target (site) | /en/tools/21-step-target | Fixed 300 dpi, continuous tone | 300, continuous |
| Process pages' 25-patch targets (site) | /en/*-calibration pages | Fixed 300 dpi, continuous tone | 300, continuous |
| Screen-printing target (site) | /en/screen-printing-calibration | 300/450/600 dpi if screened rendering | 300, AM halftone |
The site's PNG filename carries its settings: mire-{process}-{polarity}-{count}patchs.png, with a -trame-{lpi}lpi or -diffusion suffix when a screened rendering is picked. Handy if you keep several downloaded files around.
#The test
Download the site's 21-step target: the file is 1680 × 668 px, checkable in your computer's file info — 300 dpi, no variant possible. Then, in the app, generate a negative with Show the target on and move the Resolution from 300 to 600 in Effects: regenerate, and watch the file grow accordingly. The target didn't follow any setting of its own — just your negative's. The app's real screening works the same way: whatever you set for the negative, the target carries it along. See also Dithering (bitmap) in the glossary for the technique itself.