I'm trying to superimpose a graph over some video footage. I made the graph with a pure black background and exported it as a quicktime movie (millions of colors + alpha channel) using animation compression. The problem is when I set the tranfer mode in either FCP or After Effects to Screen mode, the background video bleeds slightly through the bars of the graph, which are colors like solid red, yellow and blue. I've tried using other transfer modes like add, overlay, etc. but nothing works. I'm I doing something wrong? Any suggestions?

Try making the graph in Photoshop if you have it. Make sure it has at least one layer in addition to the background. Layer 1 will be your graph, but make sure that it is transparent to the background layer below it (instead of black where you want it to be transparent). Then make the background layer transparent. Save as a PSD file and import into FCP. FCP will layer the graph over the video perfectly when you drag it to the timeline above the video layer.

I hope that makes sense.

Thanks for the advice, Ted.

Unfortunately creating the graph in Photoshop is not an option, as it uses motion (the chart flies in and the bars of the graph grow over time). I made the graph using Apple's Keynote software to save time animating the graph. Animating it as Photoshop layers in Final Cut Pro would take too long.

Do the bars grow in a linear fashion, ie upward?

The bars do grow upward in some cases, but they are in front of a grid, so I am not able to simply animate them with a mask.

Can you not simply key it using black as they key color, instead of using transfer modes?

For example, I've imported Poser avi movies into Premiere and set the Transparency to key out the background color and that seems to work well.

I've tried exporting the graphs with a solid black background and then using a chromakey filter to key it out, but it was a lot of work to get it to look decent around the edges. Plus it won't work on graphs that use dark shadows underneath the graphics. There is no Key Transfer (composite) mode in Final Cut Pro that I'm aware of.

You should be able to do a vertical wipe between the two frames to get your vertical animation.

My graphs usually have grids and other images in the background, so I can't do a simple wipe to animate the bars.