Just done a Google search, so have a look
here, where the author writes:
"
Problems with Canon FD manual lenses.
Canon FD lenses are manual-focus only lenses which Canon sold in the years before switching over to the autofocus EF system. Many, particularly those made in the late 70s and early 80s, offer excellent optical quality, have smoothly-operating metal barrels and are available quite inexpensively on the used market. So the obvious thought comes to mind - can such lenses be attached to EOS cameras?
Unfortunately the lens mounts used by the two systems are completely incompatible. FD lens mounts are smaller in diameter, have a different lens register from EF lenses, rely on mechanical levers to control lens aperture, are of a breech-lock design (rotating pressure ring) and never contain autofocus motors.* EF lens mounts are larger in diameter, are of a bayonet mount design (put lens into camera and rotate partway to lock), support electronic control of the lens aperture and the lenses usually contain autofocus motors.
So. When it comes to adapting FD lenses to EOS cameras the key difference here is the lens register incompatibility. Adapters for Canon FD-mount lenses, including the two adapter models that Canon themselves sold at one point, must deal with this incompatibility somehow. Either they contain optics (glass lens elements) to compensate for the register difference and retain infinity focus or else they don’t contain optics and don’t retain infinity focus. There’s no way around this.
Canon’s optic-containing FD-lens-on-EOS-body adapters were basically small teleconverters (1.26x) and only worked properly with a number of their longer telephoto lenses - effectively transforming them into longer slower lenses - you lost 2/3 stop. The full official list of compatible lenses is:......."
......The article continues on the website.
Cheers
Dennis