7.2 Transmissive Hardcopy Printers
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## 7.2 Transmissive Hardcopy Printers

For transmissive hardcopy printing, the relationship between luminance, L, and the printed optical density, D, is:

Equation 7-3.

where:

- L0 is the luminance of the light box with no film present

- La is the luminance contribution due to ambient illuminance reflected off the film

If film is to be printed with a density ranging from Dmin to Dmax, the final luminance will range between
and
and the j values will correspondingly range from jmin = j(Lmin) to jmax = j(Lmax).

If this span of j values is represented by an N-bit P-Value, ranging from 0 for jmin to 2N-1 for jmax, the j values will correspond to P-Values as follows:

Equation 7-4.

and the corresponding L values will be L(j(p)).

Finally, converting the L(j(p)) values to densities results in:

Equation 7-5.

### Note

Typical values for the parameters used in transmissive hardcopy printing are L0 = 2000 cd/m2, La = 10 cd/m2.

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