There is a 24-70 in the Contax yashica mount but it is not reputed to be a high quality lens like the 35-70 or the 28-85.
N lenses are for a diferent series of cameras on which the aperture on the lens is controlled electronically. Conurus converts these lenses to work on canon cameras in native mote with both autofocus and auto aperture but it is not cheap. The aperture on N lenses cannot be controlled manually other than through the N camera protocols so the lens is only useable on an N camera or if converted on a Canon camera.
Mike
Shame - I did not know that
Could you elaborate
Im after manual focus and manual aperture zoom lens for filming with the 5d
28 is not wide enough
Im after tough build quality - I thought I found (or not foud) just the thing !
S