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Alpha error?

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Scott Norris
Alpha error?
on Feb 22, 2013 at 2:28:15 am

Hey guys,

Basically I'm trying to export some rotoscoped footage for use comping in ae. Figured the best way would be a image sequence (preferably Tiff - highest quality?). When i try and render i don't have the alpha, it's just a white solid behind. If someone could point out where I'm going wrong that'd be mighty handy - thanks!

(also, i read somewhere that you have to manually add an alpha channel to the layers window - tried that and it just renders as a black screen!)


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Jeff Hinkle
Re: Alpha error?
on Feb 22, 2013 at 3:04:35 pm

Alpha channels need to be in the Channel palette, not the Layers palette.

But building a bunch of alpha channels seems like a lot of extra work. After Effects will honor Photoshop layers, so if you have everything saved as separate PSD files already, you can just bring it in as a Photoshop sequence. Or if you're working with a video file and have Photoshop Extended, you can simply export the footage out of Photoshop as a self-contained movie file. And if you haven't done the roto work yet, you could always do that in After Effects and skip Photoshop all together.

---
It is easier to destroy than to create.
More fun, too.


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Scott Norris
Re: Alpha error?
on Feb 22, 2013 at 7:20:44 pm

Thanks for the swift reply!

Miscommunication there sorry, i meant the alpha channel, not layers. But yeah; still exports black stills. The type of roto i'm trying to achieve is unachievable through ae unfortunately. I just want to export it with an alpha channel, like i can from after effects, but don't know how?


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Jeff Hinkle
Re: Alpha error?
on Feb 22, 2013 at 8:01:04 pm

If you've got your roto'd footage on a layer and the background is transparent, Command/Ctl-click on the layer's thumbnail in the Layer palette to make a selection of the opaque pixels of that layer. Switch to the Channels palette and click the "Save selection as channel" button at the bottom (looks like a little dark circle inside a white rectangle). That will make an alpha channel the exact size and shape of your roto'd image. If you've got a lot to do, you might want to set up an Action to use in an automated batch process.

But again, AE will read transparency from Photoshop layers. I'm not sure how your project is set up, or what your final goal is, but you might be able to do this faster and simpler with just your PSD file.

---
It is easier to destroy than to create.
More fun, too.


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Scott Norris
Re: Alpha error?
on Feb 22, 2013 at 8:07:36 pm

hey, thanks again for the response. following your instructions i can create an alpha layer that effectively has inverted the black and white. so i have a white image drawn on black now. Is this how it should look? or do i need to invert the selection of pixels before i create a new channel with them? Also, the layer im taking the pixels from is a video layer & so once i create this new alpha channel, i can only see the first frames worth of image - i lose the rest. any ideas? Thanks.


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Jeff Hinkle
Re: Alpha error?
on Feb 22, 2013 at 10:42:05 pm

Since you said you were saving out a sequence, I assumed you'd broken the movie into separate stills. If you're working with a video file, why not just export it out as a movie with alpha? Photoshop will generate an alpha channel for the movie file based on the layer transparency. You could even export it as a Photoshop sequence if you'd rather go that route

---
It is easier to destroy than to create.
More fun, too.


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Scott Norris
Re: Alpha error?
on Feb 23, 2013 at 7:02:23 am

Okay this sounds promising, what is the layer transparency? I only have one layer active, which is the video layer i have drawn on to.


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Scott Norris
Re: Alpha error?
on Feb 23, 2013 at 7:08:13 am

A photoshop sequence appears to have worked, so thank you very much for your time and assistance!


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