Kodak has discontinued a lot of b/w films over the years. I have questions, hopefully someone out there has answers. First..Kodak Royal Pan...ISO 400. What was its intended purpose, since Tri-x is virtually the same ISO? Ektapan..I have used it, but why was ther Ektapan and Plus-X, almost the same ISO? Super XX, ISO 200..Why is it legendary? Is it better than Tri-X? (was) Curious minds want to know.