Shadows on alpha channel render end up same colour as AE background
 

I am trying to create an animated drop shadow on a logo that I need to render out with an alpha channel for FCP. Problem is that the drop shadow when rendered has a yellow tinge, which is the default background colour in my AE project. How can I solve this issue? Is it as simple as changing the background colour on my AE project to black, or is it a little more complex than that?

Hi Shaun. I'm a little confused. Are you creating your drop shadow, using the standard effect Perspective/Drop Shadow on the logo layer? I presume you are rendering just the logo and shadow with an alpha background from AE, not keying it in FCP?

Yes, the shadow was created using the Perspective effect and I am rendering with the alpha background and not keying in FCP

Mmm. I can't replicate your problem but two thoughts:
Delete your background before rendering (but if it's the screen default colour then toggle the alpha switch at the bottom of your screen - the one with the grey squares on it and the background should disappear)
or
Precompose your logo layer with the drop shadow effect and render that
Might help?

In your render you need to render the alpha as Straight, not pre multiplied. If it's pre multiplied graduation will show through, this is useful when you want graduated transparency effects in your composition, but very troublesome if you want perfectly clean effects like baseline keys etc.

If you render the alpha as straight, you should always get clean edges.