Human Eyes to Distinguish Colors
Date：2016-12-12
The
color difference unit, NBS, is derived from the unit of color
difference formula which is established by Judd-Hunter. In 1939, the
American Bureau of Standards adopts this color difference formula and
calculates the color difference according to it. When the absolute value
is 1, it is called “The NBS Color Difference Unit”.
Since
then, people would consciously adjust the later color difference
formulas to be similar with the NBS units. The formulas such as Hunter
Lab, CIE LAB and CIE LUV are generally similar to NBS (not exactly the
same),therefore, do not mistake the color difference units calculated by
other color difference formulas are all NBS.
In
national standards GB7705-87 (lithograph), GB7706-87 (letterpress),
GB7707-87 (gravure) which promulgated by the National Bureau of
Standards, the color printings rating in the same batch and same color
according to color difference are defined as follows: General Product
ΔEab≤5.00～6.00, Fine Product ΔEab≤4.00～5.00. Meanwhile, this quality
standard is considered as a qualification for state enterprises
promotion.
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NBS Unit Color Difference
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Perception Degree of Color Difference
|
|
0．0～0.50
0.5～1.51
1.5～3
3～6
Above 6
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The Tiny Color Difference: Travel
The Smaller Color Difference: slight
The Small Color Difference: Noticeable
The Big Color Difference: appreciable
The Bigger Color Difference: much
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