Linking depth of field focus to Null? - Adobe After Effects

Focus distance is measured in pixels. All you have to do is add an expression to the Focus distance of the camera that measures the length from the null to the camera. The Expression Language Menu has a category called Vector Math . In that category you'll find the following: length(point1, point2) All you have to do is replace point1 with position and point2 with thisComp.layer("Null 1").position

The final expression looks like this:

length(position, thisComp.layer("Null 1").position)

Now, no matter where you put your null, the camera will be focused on that point. It couldn't be much simpler.

Rick

Thanks for the explanation Rick.

So if you had Null 1 and Null 2, it'd be
length(thisComp.layer(Null 1").position, thisComp.layer("Null2").position) ?

So that calculates how far apart 2 nulls are?

If the null isn't on the camera's z axis, you need to do a little vector math to align the camera's focal plane with the null. An expression like this for the camera's Focus Distance should do it:

v1 = thisComp.layer("Null 1"). position - position;
v2 = toWorldVec([0,0,1]);
dot(v1,v2)

Dan

Hey David! What are your plans for using the distance between two nulls?