movement speed

I am trying to do what everybody calls the Ken Burns effect in my project.

I have been following this tutorial which I found online:

http://library.creativecow.net/articles/ross_shane/movement_on_stills/video-tuto rial

The problem I seem to be running into is the consistency of the speed of the zoom.

I seem to get zoom outs just fine just fine lke in the video but when I apply the same priciples to a zoom in it changes speed in the middle. Either it speeds up at the end or starts off quickly.

Basically from what I can tell the reverse should apply from a zoom out. Right?

What am I doing wrong?

BF