Why are density values used for NPDC

[J]

This is probably a very dumb question but I'm very new to this and trying to understand.
It seems that GRACoL 7 does away with solid ink density targets and replaces them with L*a*b* aim points. Why then are the NPDC aim points specified in density values and not L* values?


thank you,
John

 

[meddington]

Re: Why are density values used for NPDC

>Why then are the NPDC aim points specified in density values and not L* values?

Mainly because this value would have to be officially defined with paper excluded, which is not easily done and would lead to other measurements being thrown off (solid Lab for example), that is, if your spectrophotometer will even yield paper relative Lab values. Density is easily measured relative to paper and makes for an intuitive definition for tonality...albeit a poor indicator of color, and hence a definition for neutrality in a* and b*. That said, G7 actually does officially define neutral density based on colorimetric values (from CIEXYZ_Y) as ; ND = Log10(100/Y); (where Y > 0 < 100), but again, not very intuitive to use press side.

 

[User Name]

so would it be safe to use DE cmc as a good press side tolerancing method?