This is of course because the EF-S lens doesn't necessarily light up the whole full-frame sensor. It's not designed to have to do that.
The flange distance isn't important for the focal length, but is for the lens' ability to focus at infinity.
This is of course because the EF-S lens doesn't necessarily light up the whole full-frame sensor. It's not designed to have to do that.
The flange distance isn't important for the focal length, but is for the lens' ability to focus at infinity.