@JR - focal length is measured from the sensor, so lens length isn't relevant. Still, lenses don't always deliver the indicated focal length, and at closer distances focus breathing can affect apparent focal length (for example, at 1:1 magnification, the 100L Macro IS is delivering something like a 67mm angle of view). Even ignoring focus breathing, lenses differ - I once tested an EF-S 18-200mm against my 70-200mm II, and compared to the L zoom, the 18-200 @ 200mm was giving an AoV equivalent to about 154mm (assuming the 70-200 was 'correct').
Thanks for the clarification...my bad! I knew I would learn something new everyday with this website
As for your test between your 18-200 and 70-200, wow the delta in AoV equivalent is really huge!
However, grant me this... if I saw the numbers sharper at the higher or lower end of the scale (lets say 13" or 11" etc, then it would indicated forward or back focus, this is not the case, the lens is correctly focusing at 12"
One thing is for sure the 70-300L has a lot of potential!