开云体育

I think in his example Shilesh demonstrated the difference between the two approaches we are discussing.

Curve 1 illustrates method 1: Here the printed luminosities of all lighter inks are referred to K (the common reference curve): To that end he determines the densities (for the ink setup) by those densities in the calibration plot at which the K-curve has the luminosities at which LK and LLK reach their respective minima. In his example:
??? Lmin of LK was 55% step of K
??? Lmin of LLK was 25% step of K
This method 1 corresponds to using the open square for the LLK density in my graph.

Curve 2 illustrates method 2: In this case one has to multiply the two fractions 0.55 and 0.25. This results in 0.25 * 0.55 ~ 14 for sought density of LLK. This method 2 corresponds to using the solid diamond for the LLK density in my graph.

I think in the calibration guide (p.4 of calibration.pdf) both these methods are getting mixed. Here are the sentences which are contradictory:

• Method 1: "But it's necessary to have all the relative densities to a common value".
• Method 2: "Mathematically this is very simple, just a multiply: LLK = 38% of 32.7% of 100 ... = 12.4%"? and "... the comparison is most accurate by comparing the LLK ink to the LK ink not to the K ink."

Both method yield the same result for the required density of LLK only if all ink luminosities satisfy L(K) = A - b_ink*K (with A=L(K=0) the common luminosity of the paper and different values of b_ink by for each ink). This linear relation ship holds true for very small values of K. But for larger K all L(K) curves saturate.

I hope it is clearer now.

Best,
Hendrik