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Image Matte, Track Matte, Alpha channels…
Can someone explain how to use the Image Matte keying in PPro 1.5? What kind of file (eg. Photoshop or PaintShop Pro file does it take to be the matte? How to prepare one? When would one use a Image Matte vs a Track Matte? How about what is a garbage matte? How to make one?
Perry
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3 Replies
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I guess one of my main questions is how to set alpha channels in Paintshop Pro or Photoshop for the track matte to utilize the alpha composite instead of the luma one? i.e. I tried to draw a Big Circle with a silver edge and a small circle enclosed (immiate a CD with a silver edge). If I use luma compsite, it edge does not show up. How can this be accomplished?
Perry
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Image and track mattes in a superiour track both create an area of transparency in a video clip in a track below. Your choice in the Effect settings for the image matte are to use Luma or Alpha. I typically use Luma. Create an image (720 x 480) pure white (255,255,255). Add a pure black (0,0,0) shape to the image, export as a .gif. Premiere will use the black area to create the transparency, typically in Video 2, allowing Video 1 to show thru… Apply the track matte effect to Video 2, not the track matte in Video 3.
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Rememebr that technically….Luma versus Alpha is really eactly the same thing in terms of result…
If I have a gray scale image… That’s going to be luma as you will be looking the RGB channels of the image as opposed to the A(lpha)
Alpha is convenient if you want to refernce the Alpha Channel of an RGBA image…
typically this won’t look like a gray scale image when you view it… but the alpha is built in as the fouth channel…
So really you directing the filter as to which channel(s) should it be looking at in the refernce matte image…
that’s all..
Alex Udell
Editing, Motion Graphics, and Visual FX
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