I've been having a go at a few time lapse movies using Photoshop CS5 on the Mac.
I have kind of 2 linked queries:
1) The easy way to make a movie is to use file>open and choose a batch of photos while ticking Image Sequence. However this doesn't seem to offer the option to reverse the frames which is quite important.
2) The other way I found on the web is to use a stack. I'm not entirely clear what the benefits are this way although it does allow me to reverse.
However if I go to Document Settings and change the frame rate, it doesn't seem to affect the length of the movie, whereas method 1) does invite you to set the frame rate at startup and this affects the overall length of the movie.