Learnt some good ideas from this article

It is clear as day - excelent!

Hi M O

The amount of scattering is defined on page 4, where the ABg function 'Lamb-Spec' is applied to the front face of the window. You can use Tools...Scattering...Scatter Function Viewer to see the full scattering function, and also see the total scatter given in the text at the bottom. I think this is the 'percentage scatter' value you are looking for.

M O,

I agree with you that perhaps you did miss the point. The article's summary begins with the sentence: "We used ZEMAX to measure the effects of forward scattering on the MTF and Spot Diagrams of an imaging system, quantifying the effects of veiling glare."

Showing a numerical change in MTF, caused by veiling glare, is indeed quantification. In fact, it is a very important quantification to people for whom MTF is an understood and accepted metric of imaging quality.

If you are used to seeing veiling glare listed as a percentage, then perhaps you should write a ZEMAX KB article explaining what this percentage value means, showing how it is useful in a practical sense, and demonstrating how to perform this percentage calculation in ZEMAX. That would be educational and interesting.