[QUOTE=Murray@uptowngallery;553225]nominally (7^2+17^2)^0.5 (square root of sum of squares of the side dimensions = nominal diagonal...the actual is a miniscule bit shorter, but insignificantly).
Nominally I would agree, where the aspect ratio is roughly equivalent to human vision, ie: 1:1.25 or 1:1.5. With a panorama however, it seems to me that the vertical is cut down somewhat and the horizontal is greatly expanded from our usual conception of the visual field. Accordingly, I wonder if Pythagoras should be invoked for a 7x17 to actually consist of an imaginary 7x9, or 8x10, or 9x12 (choose your own) field of view. If you choose 7x9, for instance, you get 11.4 in. or a 290 mm lens. If you choose 9x12 you get 15in. or 380mm.
Personally, I shoot a 355 when I want "normal" and it looks "normal" to me, but then again, I'm not normal.