ah, ok. I see what you mean about the blending Stwert, I just set this up quick in Maya with a cube and a sphere, and there were two nodes in the attribute editor to do with the constraint. One of which had the 'blending weight', which I guess is what you mean. But when I set up the same thing with a camera, the node with the weighting attribute wasn't there. (?) Perhaps the aim constraint would be more suitable for my purpose, as I want the elevation of the camera to taper off slightly towards the end, so the lift and helicopter travel just a little higher than the camera.
I think I need to play with some of these methods on some simple block geometry, really too tired right now.
Thanks both for your input, gives me a good basis to start tackling this and learn some new things.