Standardized Tone Value Increase Calibration Protocols across Variable Substrate Grades
Standardized TVI calibration requires substrate-relative spectral curves, M1 spectrophotometry, and dynamic CTP curve adjustments matched to sheet porosity.
Murray-Davies
Optical Density
Calculations for determining the percentage of ink coverage on a printed sheet rely on the relationship between the density of the tint and the density of the solid. The murray-davies equation provides the standard method for calculating this dot area in lithographic and flexographic printing. It assumes that the ink is perfectly transparent and that the substrate is perfectly opaque.
Physical Reality
While the formula is a staple of quality control, it does not account for the physical spreading of ink or the scattering of light within the paper fibers. Using murray-davies results in a measured dot area that is often higher than the actual geometric size of the dots on the plate. This difference is known as optical dot gain and is a critical factor in color calibration.
Practical Application
Press operators use the results from this calculation to adjust the ink keys on the press during a run. If the murray-davies value for a mid-tone screen is too high, the images will appear too dark and lose detail in the shadows. Calibrating the press to a specific target based on this formula ensures that the final product matches the approved proof.
Because it is simple to calculate, it remains the most common metric found in handheld densitometers.