Hello all, I'm new to catalyst, and am wondering how to achieve transparency on a layer, to show the layer behind.

For example, one of my cues calls for a city scape image with clouds rolling behind it. I'm putting my clouds movie on layer one, and my city scape on layer two. At the moment, I have a black background everywhere I want to have clouds show through. Unfortunately, there are a lot of dark spots in the city image, so I end up seeing clouds all over the place when I use transparent black. White has the same issue.

Is is possible to use some other color, such as bright pink, and key it out? Or, to use the transparency (alpha) of an image to cut out parts of the image? We are using photoshop to create our images, so I can save in just about any format.

Thanks!

-Landy