How to replace color background with Alpha channel?

[AudioEditor]

I've made a circle animation I want to use to illustrate that a button on a smart phone has been pushed.

It's an animation  of concentric circles interacting quickly then fading away, just about 1 second. I created it in Premiere,2018 essential graphics, but it has a black background, while the circle animation is red.  I'd like to export it but I don't want the black background. How can I export it without the black background and with an alpha channel? I turned off the "composite" in the monitor view and chose "Alpha" there but my red circle turned white so that's no good. I'm thinking I may have to make the red circle in illustrator but I don't know that program, so I hope there's some other way.  Thanks for any help!

[Meg The Dog · Accepted solution]

Place the animation on the timeline. Clicking on the wrench at the lower right corner of the Program Monitor, set the monitor to display the transparency grid:

If your animation looks correct (the transparency is correct) then export the animation from the timeline in a codec that supports a matte channel, like ProRes 4444, or QuickTime Animation.

MtD

[AudioEditor]

Meg, Thanks for your help. When I did as you directed and set Quicktime/animation codec, I still got a black background in the output.  I went back and tried it again. This time I checked X render at maximum depth (and under that) X 8-bpc + alpha. That time it rendered out my circles with an alpha channel. Yea!

[Pekeris]

Cleared up my problem.  Thank yu!!!!

[Bill in Ohio]

I just tried using a Color Key to turn the all black background to Transparent

Select the following:

"WRENCH IN PREVIEW Panel (Right bottom) > Transparency Grid (Background will stay Black)

"EFFECTS" Panel > Video Effects >  Keying >  Color Key > Drop effect on clip

EFFECT CONTROLS Panel >

fx Color Key>  Key color - use the eye dropper on the Black Background (set all colors to 0, OK) Background changes

                     >  Color Tolerance - adjust until remaining black is gone, but nonblack is intact (mine was 28 on 0-255 scale)

I did this to put the graphics behind the moving subject and other objects which did not have Black in them.