I am trying to resize two mov layers together. I would usually select both layers, hold shift to maintain their shape and drag the scale slider or layer corner inwards/outward. When I tried this the two objects changed scale at different rates and ended up quite different to each other? this only occurs when mov files are in the composition; on a separate comp with solids scaling works fine. How do you resize two mov at the same time?
The problem is that the layers are scaling at the same rate. If you look at the actual scale values. For example, if you have one layer at 100% scale and another at 90% scale, then select both and resize to 50%, the layers will be at 50% scale and 40% scale, so they have both had their scale reduced by 50% of their total 100%, not 50% of their current scale.
You can see the default behaviour here:
As far as I'm aware this is just how After Effects work and you can't change it. There are 2 main ways to get around this:
Select all the layers you want to scale, right click and select Pre-Compose...
2. Null Layer.
Create a new Null Layer (Layer → New → Null Object). Select all the layers you want to scale and parent them to the Null Object (drag the little icon under 'Parent' in the layers/timeline to the Null layer).