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How to view background as transparent instead of black
Hi,
I have a video that I’m going to project onto a wall for an art show of an animal where the background has been cut out and is an alpha channel. I’m putting video behind it in some parts and having other aftereffects drawings appear around it in other parts. I know that the alpha channel has been done correctly on the video because when i put a picture behind it in Premiere, I can see it correctly. My question is when I have nothing behind it – i just want it to be the wall where it is projected and I have the drawings which are black appearing around it – It is just showing up as a black background – so now I can’t see the drawings because they are black. It there a way to see the gray and white squares the way you can in Aftereffects so i can see what’s going on?Hope this makes sense.
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6 Replies
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Nope. In fact there is no background it is a void and it shows as black.
You can temporarily put a color matte underneath.———————————————–
Adobe Certified Expert Premiere Pro CS6
Adobe Community Professional -
So after I render it out with an alpha channel when I project it onto the wall, will it still have a black background?
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Correct, Pr will out full the full video frame, black where you have alpha.
Chris
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Never mind, misinterpreted the question
Jeff
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So is there anyway to project this image with no background at all?
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Yes, there is a way to preview with no background.
You’ll want to have a separate preview sequence – this will have two video tracks.
Video 2 = Main Edit Timeline (as a nested sequence.)
Video 1 = Checkerboard pattern that you generate (a still from whatever source you wish – this is only for your comfort that you’re seeing transparency.)For outputting the video with an alpha channel, it may be a useless exercise. Do you know that your playback program can mask the video with the alpha channel? Some VJ solutions can, but most standard players won’t be able to.
Regardless – here’s a starter.
In order to render an alpha channel in to your video, you may have to output 3 times:
- 1x Video RGB
- 1x Video Alpha – see following notes
- 1x Composite from AE
The reason I say 3x with once from AE is that I don’t know of a way to output the alpha channel as an embedded alpha from within Premiere – I can only see options to output composite video.
You can, however, create an sequence to output the alpha as a composite video, which you can then combine to a composite video in After Effects. Nest your main edit timeline as listed above, but remove the checkerboard pattern. Then apply an effect such as “4-Color Gradient” to modify only the non-transparent pixels. Change the effect controls to all white. The result should be a black & white video that shows only white where the video is not transparent (I.E. where it will show up on the projection surface) and that it shows only black where the video should be see-through.
I’m out of time at the moment, but if this is still relevant and you’d like more help, reply here to my comment and I’ll try to write up the next steps. If you want to try to figure it out on your own, search for “track matte” in the After Effects forums.
Best of luck!
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