Application of Reflection Density Measurement and Colorimetry in Printing (4)

3.26 screen frequency/screen number; screen ruling

The number of image elements such as dots or lines in the highest value direction, the number of unit length. Unit: cm-1.

3.27 screen width

The reciprocal of the number of lines. Unit: cm.

3.28 Solid on the ground

A dot-free structure image with uniform coloring density and coverage of 100%.

3.29 Spectral product spectral product

The spectral power of the incident light flux and the product of the relative wavelength of the spectral response of the receiver.

3.30 (receiver's) spectral response(of the receiver)

The spectral sensitivity of the photodetector and the spectral transmittance and product of the optical element associated with it.

3.31 tone value; dot area coverage percentage (on the print) A tone value; dot area (on a print), A

The percentage of dot area coverage of a monochrome ink on a halftone print (if light scattering or other optical phenomena on the substrate are negligible). The formula is: A(%)=100×[1-10-(Dt-Do]/[1-10-(Ds-D0]]

Among them: D0 is the reflection density of the non-printing part of the printing substrate;

Ds is the field reflection density;

Dt is the reflection density at the dot site.

Or its equivalent formula: A(%)=100×(R0-Rt)/(R0-RS)

Among them: R0 is the reflectivity of the non-printing part of the printing substrate;

RS is the field reflectance;

Rt is the reflectance of the dot site.

Note: * Also called "equivalent dot area" or "full dot area";

*Synonyms (mesh area) apply only to halftone images composed of dots;

* This definition can be used for approximate values ​​of some plate gradation values;

* In general, the tone value indicated in digital electronic files is considered to be the same as the data on the software of the imagesetter.

* This formula is the Murray-Davies formula;

3.32 tone value; dot area coverage percentage (positive picture color separation) A tone value; dot area (on a half-tone film of positive polarity), A

The formula is: A(%)=100×[1-10-(Dt-Do]/[1-10-(Ds-D0]]

Among them: D0 is the transmission density of the blank part on the halftone film;

Ds is the degree of transmission in the field;

Dt is the transmission density of the dot site.

3.33 tone value; dot area coverage percentage (negative picture on a color separation slice) A tone value; dot area (on a half-tone film of negative polarity), A

The formula is: A(%)=100-100×[1-10-(Dt-Do)/[1-10-(Ds-D0)]

Among them: D0 is the transmission density of the blank part on the halftone film;

Ds is the degree of transmission in the field;

Dt is the transmission density of the dot site.