Originally Posted by wickerprints
Actually, at the 150mm focal length, you get a 36x24mm image circle for free. There would be no weight difference at all if it was designed for full frame, APS-C, or even a mobile phone or digicam. The only time there is a difference in weight is when the focal length starts getting close to twice the format diagonal (and it really gets bad at half the diagonal).
Originally Posted by wickerprints
The IS might add a half-pound, but USM wouldn't add anything. The manual focus features on cine lenses probably weigh a lot, though.