My wife asked me a question I could not answer. Why is Kodachrome 64, "64"? How did Kodak decide to make that rather unusual number the ASA/ISO when they first released the film (originally as Kodachrome- X, I believe) back in the early 60s? Why not ASA 50 or 75 or 100, or something like that? They already had the ASA 25 film, Kodachrome-II. Wouldn't it have been logical to make the "other" version of the stuff a nice, neat multiple of that number, either one or two stops faster? Is there some special thing about a square root number like 64 that I don't know?