after effects fx with black back ground

[Joseph W. bourke]

Generally, whenever you see an effect like this with a black background, it’s meant to be composited in Additive mode, a mode which sees the pixels which are brighter than black, and adds their value to the underlying pixels. The black disappears, but this effect only works over another layer.

In this case, there a couple of ways to go: you could use Additive mode, or you could get your hands on the free Unmult plugin, which you can find here:

https://www.redgiantsoftware.com/products/free/#list

This one “unmultiplies” the pixels from the black ones, giving you an alpha channel. It’s really up to you, depending on the look you’re going for, which way you want to go.

Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com

[Andrew Somers]

I have a couple of recent posts that discuss how to work with black screen elements that you might find useful:

https://forums.creativecow.net/readpost/2/1013480

https://forums.creativecow.net/readpost/2/1013568

As Joseph said, the unmult plugin can be helpful, at least when it works. Unfortunately, there are a lot of cases where it does not work as expected in black screen – one tip with unmult is to put a LEVELS effect above it in the stack, to adjust and/or clip the black. In some cases, you’ll want to use unmult along with levels to create an alpha channel layer, then use that layer as an alpha for the layer with the image you are trying to comp.

[Nick Tallents]

Using the “screen” layer blending mode should remove all black.

“Life’s a progress bar”