Technical Issues - Diabatic Transmittance Scale

The Schott diabatic transmittance scale [1-log(log(1/t))] conveniently displays passbands and blocking regions on the same graph. This scale is now available in the DESIGN 2.61.1040 and MEASURE 2.51.0220 FSPlot Module. There is a choice of (0-1) or (0-100%) ranges.

Assuming that the vertical axis is transmittance, click Transmittance Format in the FSPlot Setup menu to select linear or diabatic formats. Annotations are added in the usual way, and automatic annotations as shown below are supported. Annotations developed for the 0-100% linear scale will work on the 0-100% diabatic scale.

Although FSPlot can also display %T and optical density on the same graph, the diabatic scale has the clear advantage when displaying bandwidth in the blocking zone. It should be mentioned that the usual definition of diabatic is different from Schott's (and FilmStar's) definition.

Users anxious to try this example will find FnumDiabatic.faw and BandWidthPlotII.bas in As usual, copy *.faw to c:\Winfilm\Designs and *.bas to c:\Winfilm\Basic32.

Diabatic transmittance scales were added to the Interactor in DESIGN 2.61.1050. Note the Trns Format option under Graph Axes in the Interactor option box.


The diabatic %T range is 2*E-6 to ~97.5. While this satisfies most requirements, there are cases where data lies outside the range.

Check Setup.. Transmittance Format.. Auto Scale Diabatic to specify a range computed from the plotted data.

The option is stored with Graph Axes. Clicking View.. Zoom Mode (or Setup.. Zoom Mode in the Interactor) also displays the full range.