Sizes of the letters

I remember reading here somewhere the "ideal" dimensions of the letters... it was something like: t, s, th = 1/4th the line; f, p, nd, d = 1/2 the line; b, v, ted, md = the full line.

But when I was going through a lesson in the Simplified manual, I noticed that in phrases like "would be", the two letters are the same size, whereas if these proportions were followed, the D would be smaller than the B...

I guess I got mixed up somewhere. Can someone tell me the proper relationships of size among the letters? Which ones are the same height as others?

Thanks a lot :)

(by niftyboy1 for everyone)