John (Gradient) I think you may find that the lenses designed for 1.6 crop sensors do not fit on the cams that have larger sensors.  These lenses in the Canon range are the EFs lenses and will only fit on the 1.6 crop cams. 

Lenses designed for full frame sensors offer the advantage of using the 'sweet spot' at the centre of the lens when used on smaller sensors and are compatible with the whole range of cams whatever their sensor size.  

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html