How to use it
Select your layer and open the Scale property in the timeline.
Hold Alt (Win) / Option (Mac) and click the stopwatch icon next to Scale to open the expression editor.
Delete the default expression, paste the code below, and press Enter to confirm.
Set at least two keyframes on the Scale property. The expression will interpolate between them exponentially.
Expression
if (num_keys >1 && key(num_keys).time > time && key(1).time <= time){
k = nearest_key(time).index;
if (key(k).time <= time) {
a = k;
} else {
a = k-1;
}
b = a+1;
a_val = key(a)[0];
b_val = key(b)[0];
a_time = key(a).time;
b_time = key(b).time;
if (a_val == 0) { a_val = .1; }
if (b_val == 0) { b_val = .1; }
x = Math.log(b_val) / Math.log(a_val);
exp = linear(time, a_time, b_time, 1, x);
val = Math.pow(a_val, exp);
[val, val];
} else {
value;
}What it does
Standard After Effects interpolation uses linear or bezier curves. This expression replaces that with an exponential interpolation: the scale grows faster the larger it already is, which mimics how real-world objects appear to accelerate when expanding. The result feels natural in a way that ease curves can't fully achieve.
Note: if a keyframe value is 0, it's nudged to 0.1 to avoid a log(0) error — this is invisible in practice.