Premultiplication in FCP?

[David Bogie]

How the alpha is interpreted is set on the item properties. You can right-click or control-click on the alpha to get a popup menu. However, you may have to go back to the original application if the alpha was improperly created. FCP cannot correct bad files.

see the manual for alpha types. It’s all there.

bogiesan

This is my standard sigfile so do not take it personally: “For crying out loud, read the freakin’ manual.”

[Harryjf]

These aren’t “bad” files. They are rendered properly… in this case out of After Effects. They are files with semi transparency in the alpha.. nothing odd or incorrect.

Most compositing apps (AE, Flint, Flame, Shake, Combustion, etc) have either a “straight” or “premultiply” method of interpretting an alpha. “Premultiply” removes a background color defined by the user… usually black.

Now, I realize that FCP isn’t a compositing application. But, it certainly isn’t uncommon to render a foreground animation with an alpha to overlay in FCP.

So, it looks like there is no premultiply option in FCP? This is very odd.

[Harryjf]

AHA.. found it. FCP refers to it as “black” or “white” rather than ‘premultiply’ with a color picker.

Works for me.