Source hierarchy
Print Prep Lab prefers a published standard or government measurement definition for fixed physical facts, official software documentation for image-processing terminology, and a print provider's own specification for provider-specific production requirements.
A secondary article may help explain a concept, but it is not used to override a primary source. Examples created by Print Prep Lab are labeled as examples and show enough inputs for the arithmetic to be repeated.
Paper and physical dimensions
ISO A-series trim dimensions are based on ISO 216:2007. The A-series relationship and listed millimetre dimensions are treated as physical standards, not as fixed pixel dimensions.
North American paper and common photo formats are stored using their native inch measurements. Metric equivalents use the exact inch conversion maintained by the United States National Institute of Standards and Technology: one inch is exactly 25.4 millimetres.
Image resolution terminology
Adobe Photoshop documentation is used as a reference for the relationship among pixel dimensions, document size, PPI and resampling. Print Prep Lab uses PPI for image pixels per printed inch and reserves DPI for printer output dots, even when everyday print-shop instructions use the terms interchangeably.
A metadata resolution tag is not treated as new image detail. Any calculation that claims to assess print readiness begins with the file's real pixel width and height and the intended post-crop physical size.
Bleed and production requirements
There is no universal bleed, safe-margin, color-profile or minimum-PPI rule for every printer and product. Values such as 3 mm bleed, 0.125 inch bleed, 150 PPI, 240 PPI and 300 PPI are presented as common planning examples only.
The written specification from the company producing the work takes precedence. Guide pages explain why the values matter and calculator inputs remain editable so a visitor can use the provider's actual requirement.
Verification policy
Calculation rules, standard presets, unit conversions, rounding boundaries and invalid-input behavior are covered by deterministic tests. Key examples in guide tables are checked against the same underlying formulas used by the interactive tools.
Source-dependent guidance is dated and rechecked when a referenced standard, official documentation or common production practice changes. A material correction updates both the affected page and its review date rather than silently changing only a table cell.
Corrections and transparency
Every public guide links to its relevant sources or to this methodology. Visitors can report a conflicting standard or calculation through the Contact page without uploading the private image itself.
Print Prep Lab does not claim affiliation with ISO, NIST, Adobe, Google, Microsoft or any print provider. Links identify the evidence used; trademarks remain the property of their owners.
Primary references and what each one supports
A source is useful only when its role is clear. The links below separate fixed standards and definitions from software terminology and provider-specific production instructions.