In his famous article Modifying the Canon EF-S 18-55/3.5-5.6 lens for use on a Canon EOS 10D, Bob gives a warning in big and bold letters: IF YOU PUT THIS LENS ON A CAMERA WITH A LARGER MIRROR, YOU'RE ASKING FOR A DISASTER. On any film based body, or on a 1Ds or probably on a 1D, the mirror will HIT THE LENS AND CAUSE DAMAGE. My question is: Why? Once the 18-55 became an EF lens, why can't if function just like any other EF lens which can be mounted on any EOS body? In other words, what makes the modified lens different from any other "naturally born" EF lens? I know I am missing something - and it is probably very basic - but it simply escape my eyes (and, more importantly, my brain.....). Therefore I appeal to all those people with less restrictive brains :- )) to unveil the veil from my eyes. TIA. Happy shooting, Yakim.