sentences:  EF-S lenses can only be used on Canon digital cameras that use the APS-C sensor, for example the 400D (EOS Digital Rebel XTi) and the 40D.EF-S lenses can be distinguished by a white dot on the mount ring, as opposed to the red dot seen on standard EF lenses.Note that while an EF-S lens cannot be mounted on a camera that uses the EF mount, EF lenses can be mounted on cameras designed for the EF-S standard