# trans or glass material, rectangular, luminous, opening problem

Hi Christian,

thank you very much for your detailed answer, i think the biggest problem i am confronted with are these different terms.
As i understand:
transmissivity is the amount of light that is not absorbed inside an object, varies between 0and 1, not taking in consideration the reflection
total transmittance the amount of light, that passes through an object, taking in consideration the index of refraction and is less than the transmissivity
But what is transmission ?

That's my mistake -- I should have said "transmissivity" rather than transmission. A transmission is the thing in your car that shifts gears... In fact, I think the term is used interchangeably in a more informal context with total transmittance.

Total transmittance takes into account reflections and interreflections (and absorbtion) inside the glass, and is the easiest value to measure.

As i want to apply the color and transmission of this color filter to the glass i got these values from LEE:
Transmission Y%: 62.4 ; Absorption: 0.21 ; as well as a Spectrum from which i calculated the xy chromaticity values with the mgfilt command: cxy 0.2884 0.3034
They have precalculated XYZ and Yxy values for different sources, but i want to apply my own source at different dim and color temperature levels. http://www.leefilters.com/LPFD.asp?PageID=193
To get my RGB values, i have to calculate the XYZ values and for that i need Y! Can i take 0.624 ?

Actually, the Y value of transmittance can change for different light sources. What you should do is multiply the value you were given (0.624) by the Y you get with your source spectrum, divided by the Y you get when you use their reference source spectrum. The confusing part is that you need to normalize the two spectra using the Y value computed from each WITHOUT your glass transmittance spectrum.

Is this clear enough? I know it's confusing, but I don't know how to explain it any better without adding a bunch of pictures and diagrams.

-Greg