Hi Greg,

thank you again and YES it is confusing!

Actually, the Y value of transmittance can change for different light sources.

Forget my other question, at first i want to make sure that i model a simple filter in the right way.

And that is why i want to stick to the values LEE gives for a 3200K lamp.

These are: X= 58.8 , Y=62.4 , Z=37.2

with xyz_srgb.cal i get: R= 76.088002 G=61.6146944 B= 29.8622268, ( i want to calculate this with the D65 white point)

As the filter won't have a bigger transmission than 1, i divide through 100.

Now i get values of: R= .761 G= .616 B= .299;

If i apply these to glass polygon i get a yellow/orange filter with my tungsten 3200 K source in the scene.

Then is subtract 1 from RGB = .239 , .384, .701;

These values should now represent my blue filter, and it looks quite good!

void glass LeeGlass

0

3 .239 .384 .701

Am i right up to now?

These values would then be my normal transmittance. In order to model a disc of 'real'colored glass (e.g. n=1.52) i would apply these values to 'trans.cal' how you suggested an get the transmissivity.

rcalc -f trans.cal -e '$1=tn($1)'

.239

0.260699013

.384

0.418782103

.701

0.763929466

Am i right here too?

Now i want to triple the effect of the filter, that means have 3 blue filters in a row. My Y=.624 would then be Y� = .243, can i simply multiply my normal transmittance of RGB with this factor to get the triple effect?

I know these are pretty simple questions, but as i plan to use the 'trans' material later i want to make sure to be on the right way!

Christian