How to split colour-difference deviation from the practices that get mixed with it
Deviation is against the sample sheet. Within-lot variation is another matter. Cyan, magenta, and black commonly use ΔEab 4, yellow commonly 5, and hue commonly ΔH 3.
Deviation is against the sample sheet. Within-lot variation is another matter. Cyan, magenta, and black commonly use ΔEab 4, yellow commonly 5, and hue commonly ΔH 3.
It is not the number next to it
Do not treat ΔEab 5 as the variation allowed from sheet to sheet. Variation looks at another set of numbers, not this one. Get the name wrong and the later adjustment and the statistics will both be wrong.
Split them
| Item | Do this | Do not |
|---|---|---|
| Deviation from the signed sample | Deviation is against the sample sheet. Within-lot variation is another matter. Cyan, magenta, and black commonly use ΔEab 4, yellow commonly 5, and hue commonly ΔH 3. | Write only a feeling |
| A common mistake | Do not treat ΔEab 5 as the variation allowed from sheet to sheet. Variation looks at another set of numbers, not this one. | Carry the mistake forward |
| What to keep | The report must state ΔEab, which signed sample it is against, the M condition, the geometry, and the backing. If one item is missing, do not call it a pass. | Leave only the word pass |
Check before you name it
- First see whether the contract says deviation or variation.
- Note the geometry, the M condition, and the backing.
- Compare only two readings taken under the same conditions.
