Simple Algorithm for Calculating Exposure Increase when Using *Front Rise*?

[cosmicexplosion]

Sounds like a small problem.
But if its a sky that is bright and potentially over exposed by a poofteenth then a. Your film will Handel it and b. just under expose a bit. C. Best to reel of a few sheets in a test situation.
My one cent.

[Sevo]

As I am sitting here in Florida, separated from my library of optics books, I have to say that this is what is referred to as the Cosine to the Fourth Law.

For a meniscus-and-aperture lens or simple symmetric double achromats, yes. YMMV with more complex lenses, even more so with wide angle ones - the Russar, Super Angulon and later successors entirely break with that rule.