Colin, I have nothing to add to what Bjørn says.
I tend to avoid closer objects in my panos. Fortunately most of my cityscapes (whether they are successful photographs
) have been shot from the sixth floor of the emergency stairs, and I try to hold the camera as horizontally as possible not only sideways but also along the optical axis. As a result, the closest object in my final stitched images will be at least tens of meters away, which helps me avoid parallax.
