Here's my problem. I have an image that is showing at 90%, and I want to shrink it to 65% in five seconds, but the grow/shrink behavior always wants to start at the original 100% size. I'm almost certain this has been covered before, but I haven't found a post.
You can certainly do what you're asking. Behaviors usually modify the parameters they affect...not replace them. In your case, you'd start by setting the object's Scale to what you want it to start at, say 90%. Then you apply the Grow/Shrink behavior and set the Increment popup to 'Ramp to Final Value'. You'd then put in a negative percentage to start shrinking. So far, so good.
Now here comes the non-obvious part:
The Scale To amount in the behavior is a percentage of your *starting* value (the value before the behavior takes effect), NOT an absolute percentage. If you put in -25%, you might figure that it would mean 90% - 25% = 65%. But, again, it's based on a percentage of the *starting* value (90%), so putting in -25% would have your object's scale ending at 67.5%
To get the correct percentage, you do a little math:
65 / 90 = 0.72
1 - 0.72 = 0.28 = 28%
So, if you put -28% into the behavior's Scale To, your object's Scale will reach 65% at the end of the behavior (I rounded a little). You can trim the behavior to whatever length you want, to get the speed you'd like.
Apple should probably make this aspect of the behavior a little more straightforward, as you could just set a couple keyframes at 90% and 65% and move on with your life.
Worked like a charm. I keep looking for info that would give the sizes. I keep looking for a fill in space for width and height.. then find those percentages. I had to figure a way to count to 2 just to get the upgrade from Motion 1... now I'm supposed to learn percentages. I'm beginning to think this is Apple's little plot to attempt to get people to learn Math... :)