Here we will introduce some FAQs about Relative Illumination in 4 topcis:
* How is Relative Illumination calculated
* Considering Fresnel loss
* Situations that Relative Illumination cannot calculate
* Relative Illumination in systems with FOV > 90 degrees
* Cosine fourth Law
It's suggested to see also this forum post:
That is great indeed!
It should be remembered that cos^4 is not a 'Law', it is simply the result you get with a simple system with no aberration. Distortion is the biggest (but not the only) effect is determining non-cos^4 behavior. If cos^4 was a Law, you woudn't need to compute it based on solid geometry!
There is an excellent paper about this from Ronian Sew on LinkedIn.