ADOBE AFTER EFFECTS: Forum Expressions Tutorials Creative Cloud

Screen blending mode without a BG

COW Forums : Adobe After Effects

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Orion McCaw
Screen blending mode without a BG
on Sep 24, 2015 at 6:08:18 am

Hey, I have a lot of footage that I'm using for a planetarium show that was shot at night and I've been using the screen blending mode plus a few masks to cut out the sky and put a star field in the BG. I've found this the fastest way with the best results. I was wondering, however, if there is a trick to use the screen blending mode without a BG in the comp. This way I could create a video with an alpha channel and use it over a bunch of different star fields. Or maybe there is a faster way to do this with a luma key?

Thanks


Return to posts index

Kalle Kannisto
Re: Screen blending mode without a BG
on Sep 24, 2015 at 9:13:52 am

Perhaps I'm not understanding the problem, but why not just composite it in screen mode for all videos?


Return to posts index

Dave LaRonde
Re: Screen blending mode without a BG
on Sep 24, 2015 at 3:33:56 pm

I guess your screen trick doesn't work in all cases. That's because you have to isolate the foreground from the sky in the background. Once you've isolated the foreground, putting in a new background is a snap.

But sometimes isolating the foreground can be a challenge.

Depending on the nature of the foreground, it can be easy or difficult... and there are many techniques that can be used, and each better-suited for one kind of foreground than another. Without a look at the foregrounds, it's pretty useless to recommend a technique.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


Return to posts index


Orion McCaw
Re: Screen blending mode without a BG
on Sep 25, 2015 at 6:52:34 am

I'll try to explain this a little clearer. I like the way the blending mode screen works because it's simple and quick for all the footage I've had to do this to. the only problem is that I need to layer a star field behind the footage for the blending mode to work. this is okay except that sometimes I use the same video clip in different parts of my show which require different star fields in the BG. so this brings me to my question.

I'm wondering if any of you talented AE wizards out there know of any tricks so that I don't require a BG to use the screen blending mode. This would allow me to remove the sky, render it out once with an alpha channel, and use it on all my star fields (in Premiere). Of course without doing anything, if I have the screen blending mode selected and no BG then I don't have a transparent sky.

I'm self taught with this stuff so I'm not sure if this is even possible or not but I thought I'd ask you folks. Maybe it's easier to key out the sky another way

Here's an example of one of the shots I'm working with. (this is one of the harder shots. for this to work I would add 2 of the video files into the comp, set the bottom one to screen, and do a rough mask around the ground stuff so that any black on the ground isn't removed)


Return to posts index

Kalle Kannisto
Re: Screen blending mode without a BG
on Sep 25, 2015 at 11:41:20 am

Premiere has a Screen blending mode, which is why I don't still see the problem with using Screen mode for everything.

Maybe an example where it doesn't work?


Return to posts index

Orion McCaw
Re: Screen blending mode without a BG
on Sep 25, 2015 at 5:46:16 pm

oh I'm being silly, I'm fairly new to premiere and now that you mention it, it makes total sense that it also has a screen blending mode. I'll play around with that and see if I can accomplish what I'm going for.

Thanks for the reminder.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]