Rollei ATP
Rollei Ortho 25
The base of a film and unexposed emulsion may look clear; but, some film is more clear then others. For example; Rollei Ortho 25 has a uniformly clear base across the entire visible spectrum. TMax is also uniformley clear; but, the amount of transmittance is lower. The maximum transmittance of TMax is 58% while the maximum transmittance of Rollei Ortho is 70%.
Note: These scans were produced on an HP 8450A UV-Vis Spectrophotometer and plotted using an HP 7550 pen plotter. Both pieces of equipment were manufactured in the early 1980's.
There is a good piece of software called GraphClick which will interpret scans of plotted data and extract the data points.