Print planning
Print size, density, and physical output: what the math can tell you
Print planning starts with the available pixel grid and the intended physical size. Density is a useful planning ratio, but it does not manufacture detail, control a printer, or guarantee the quality of a physical result.
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Calculate before you resample
A 3000-pixel-wide image intended for a 10-inch width works out to 300 pixels per inch. The same source intended for a 20-inch width works out to 150 pixels per inch. Nothing in the original changed; the available detail is simply distributed over a different physical size.
This calculation is more useful than declaring a file “300 DPI” without a physical target. It exposes the real decision: keep the planned print small, obtain a higher-resolution source, accept a different viewing distance, or test a proof print.
Worked example: two possible print sizes from one source
Take a 2400 × 1800 image. At 300 PPI it plans to 8 × 6 inches. At 150 PPI it plans to 16 × 12 inches. Both figures are calculations from the same pixels, not competing facts about the file.
If a print lab asks for 300 PPI metadata, update or resample only after you know whether its workflow checks a density label, pixel count, or final physical canvas. A requirement can be technical, visual, or both, and those are not interchangeable.
| Pixel grid | Planning density | Calculated physical size |
|---|---|---|
| 2400 × 1800 | 300 PPI | 8 × 6 inches |
| 2400 × 1800 | 150 PPI | 16 × 12 inches |
| 2400 × 1800 | No trustworthy density target | Physical size is an assumption, not a file fact |
Resampling changes the grid; metadata changes the interpretation
Changing the density metadata tells compatible software how to map existing pixels to inches. Resampling creates a different grid by adding or removing samples. Enlarging can make a file fit a requested canvas, but it cannot recover source detail that was never captured.
The difference matters for document scans and signatures. A superficially larger file can still have soft edges, unreadable marks, or compression artefacts at the intended physical size. Inspect at the target size rather than trusting the number alone.
A proof is still a separate review step
Printer driver settings, paper, ink, viewing distance, colour conversion, and the recipient’s scaling settings all affect a physical print. A calculated PPI is a planning signal, not a certification of print quality.
For consequential output, make a labelled proof from a copy, compare it at the intended distance, and preserve the source. The printer or publishing service remains responsible for its own current acceptance and production controls.
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