expression question

[Filip Vandueren]

Try this:

Assuming you want maskexpansion to be 0 at scale 100 ->

scaleFactor=0.1;
(thisComp.layer("White Solid 2").scale[0]-100)/scaleFactor;

Change the “Layer 1” to the name of your layer,
and change the variable scaleFactor, to control how fast the maskexpansion works.
0.1 means a scale of 200 will give a maskexpansion of (200-100)*0.1 = 10 pixels.

Hope that’s clear.