Blackmagic Forum

I simply want to make a select area within a clip transparent, seems simple enough but I can't find any way of doing this. I made a power window around the area I wanted to change in the color tab, but I can't find any way of adjusting the opacity of just the selected area. The only opacity related control I found in the color tab merely changes the opacity of the color correction. Am I missing something simple, or is this even possible?

You're going to have to explain what you're trying to do in a different way. Power Window Opacity is exactly what it sounds like.

But what you're describing sounds like a visual effect where you're trying to get a piece of an image to actually become transparent and reveal the background behind it. Is that what you mean?

If so, that's not easily possible (or at least is highly impractical) unless you shoot in front of green screen, composite a foreground over a background, and then adjust the opacity of the key as needed. Or maybe I'm confused, I dunno.

If you put two clips on top of each other in the timeline, a power window on the upper clip can be used to cut through to the lower clip if you use a alpha output on your upper tree....inverting the window would cause a hole where the window is...but as Marc said, you request is a bit vague.

Actually, the OP's request makes perfect sense to me. And I found this post by looking for that.

I want a circular wipe to make the first clip "shrink" in a circular fashion to reveal the layer below.
The built-in Oval Iris transition doesn't do it as it can't be inverted, inversion being different to reverse. (If I swap the transition curve points 100->0, 0->100, the wipe jsut works backwards, cutting to the second clip, then transitioning back to the first clip. ( = wrong))

When I say shrink, I mean a circular crop not zooming.

I thought that perhaps I could emulate this with a power window controlling opacity of the first clip, but you're suggesting this is not possible?

Surely this isn't such a strange request?


All the best,
Dax.

This is how you do it: viewtopic.php?f=21&t=70131