What is paper white, and why it changes Delta E
Paper white is the colour of the unprinted paper. Absolute comparison folds the paper-white difference into every patch, so a paper gap of 3 colour-difference units moves the solid even when the ink did not change. Relative comparison lines up paper white first, then compares ink. The report must say which one you used, or a paper difference will be called an ink difference.
Paper white is the colour of the unprinted paper. Absolute comparison folds the paper-white difference into every patch, so a paper gap of 3 colour-difference units moves the solid even when the ink did not change. Relative comparison lines up paper white first, then compares ink. The report must say which one you used, or a paper difference will be called an ink difference.
Did the gap come from paper or from ink
The same bucket of cyan on a yellowish board and on a bluish coated sheet: absolute colour difference counts the yellow and the blue of the paper. If you only watch the solid, you will chase an ink that is not the problem. Read paper white on both sheets first. If paper white already sits outside the range the customer gave, later solid fails must note that they include paper white. If the customer wants the whole thing, paper included, to look alike, use absolute, and the paper must change or the customer must agree. If the customer wants the ink to look alike and the papers are allowed to differ, use relative, and put the paper-white colour difference on the first line of the report.
Do not use relative on paper white and absolute on solids in the same report without saying so.
How to report
| What the customer wants | Paper white | Solid |
|---|---|---|
| Whole thing, paper included, looks alike | Absolute; if paper white fails, say paper first | Absolute |
| Ink only; paper may differ | Paper-white colour difference on its own | Relative |
| Not written | Ask first | Do not pick one and fail the sheet |
When you record, write
- Paper white Lab* on its own line.
- Absolute or relative.
- If paper white failed, do not write only a solid fail.
