Keying with an alpha channel

I have a client that needs some footage that we shot over green screen delivered to them with the green keyed out and an alpha channel already in place. The end deliverable that they are looking for is the talent over an "invisible" background that they can simply drag and drop into FCP without having to key it themselves.
So my question is, how do I key out the green and an add alpha channel to preserve the "invisibility" of what was once green?
I hope that question makes some sense!
Thanks!

The most straightforward solution is to export your keyed sequences
to Animation, PNG, or JPEG 2000 using millions of colors +.
Make sure the sequence is NOT RENDERED before you export.
(In other words, if you want to render and preview to make sure it's good,
do that, but delete your render file before exporting.) The only problem
is that the resulting files are huge and will really bog down your client's
edit.
Another solution is to export two files per clip, with the second file
being a black-and-white version of the alpha channel.
To create the second clip, add the Channel Swap filter with
red, green, and blue all coming from alpha.
Then your client places the two files over each other, with
the "alpha" clip below the regular version, and the Composite
Mode of the upper clip set to Travel Matte - Luma.
In fact, if your client already has the clips, you can just
send them the alpha versions.
The big advantage of the second solution is that you can
stay in the same codec, which should make your client's
editing go a lot faster.

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Thanks Fran,
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greetings gurus... I'm working in FCP 5.1 with DVCPRO HD footage 720p @23.98fps. I have an edited sequence of green screen footage that I am happy with. I then keyed out the green from the original source footage and exported that footage with an alpha channel (the background keyed out in AE7). My goal is to open my FCP project and replace the original source footage with the new keyed out footage so that my edit remains in tact but now with a keyed out background. I'm using the reconnect media function in FCP and of course the footage is replaced, but without the alpha channel.
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it may be that for whatever reason FCP is not interpreting the alpha channel correctly when you use the reconnect option. for example, the reconnect option may assume that clip properties are unchanged. this may be esspecially true within the timeline, where instance properties are preserved.
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When I make semitransparent animations with bright lighting effects, they look great in AE but I can't seem to find any way to bring them over to Final Cut and get them to look like they should.
I've attached this example of a bug with a screenshot from AE on the left and from FCP on the right. The colors dim and the vibrant blue gradients get flattened into a dull greenish color.
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Thanks so much for your ideas. I'd already tried experimenting with a number of color management options, including 'Preserve RGB' and turning off 'Convert to Linear Light' but they didn't fix it. I had also already tried using the "None" option from the codec menu.
I pulled it back into AE, and it looks the same as it did in FCP.
I'm starting to think the issue has something to do with AE rendering to a file differently than the way it renders to the canvas. For example, here's a fast moving 50% opaque superwhite shape in the AE canvas:
I rendered this using Animation + Alpha using Best settings and 32-bit float, and reimported it into AE:
I think the answer may lie in the fact that the first image looks solid white in some places, even though it is 50% transparent. It's almost like the excessive RGB values "bleed" over to the alpha channel. The rendered image (probably correctly) looks grey because it represents white at 50% opacity.
What I want to do though, is find a way to make my render look like my canvas. So it seems I need to do two things to the image:
1. Find a way to increase opacity in areas of excessive white, so that they are not grey in the render.
2. Find a way to "bake" the superwhite colors to a level below 100% white so that they show up in the render.
I tried the "Alpha from Max Color" effect and this seems to get kind of close, but unfortunately it discards other parts of the alpha channel (like drop shadows).
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I am pulling my hair out trying to encode a green screen video that will play on a website so the website shows through the transparent alpha channel. Problem is when I encode to .flv or .mp4 the alpha channel is never retained even when I check "encode alpha channel" in the .flv export setting window. I have downloaded a trial version of Sorenson Squeeze and even that couldn't retain the alpha channel.
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Attempting to export directly from AI to .PSD or .PNG is a wasted effort and the results may not even be recognized by Final Cut.
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Hi!
I'm stuck with something that I think might have a simple solution:
I need my video to have an alpha channel while still keeping all the RGB information in place too. This is for Syntheyes, which can take the alpha channel for a video and use it as a garbage matte while tracking.
The problem is that if I draw a mask around my video and then export as a PNG (with alpha), the RGB information seems to be gone even when I choose to ignore the alpha channel. I know how to edit the alpha channel in Photoshop while still keeping the RGB elements untouched, but how should I do that in AE?
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Okay I will answer my own question:
This worked as soon as I did a proper export as a PNG image sequence. I did my tests with only single frames by using the "save frame as file" -function, which did not work properly (the rbg information was gone).
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Recently did a large project of creating alpha channels from green screen footage.
Made the timelines 4444 and tried to output.
If I export as Quicktime, I get the timecode but not the Alpha channel.
If I export as Quicktime Conversion, I can get the Alpha channel, but not the timecode.
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With the other, you can get any sort of converted output you can input, including ProRes 4444 and Alpha, but unfortunately not the Timecode track.
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Hi!
I'm trying to use the motion tile effect to fill transparent edges that are the result of stabilization with the prodad mercalli plugin. The problem is however that because the stabilization hasn't been done using keyframe movement in AE, it sees the transparent edges as part of the frame and applies the motion tile so that the transparent areas stay intact. In other words the motion tile effect doesn't see that the image is moving around because only the alpha channel is changing.
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Hi and thank you for helping out!
Unfortunately I didn't get this to work with shift channels. I'm not sure what you meant by separating the components? I put shift channels on the videoclip and told it to use alpha from the video of the alpha.
Actually I'm a bit confused on why shift channels should help. The way I see it, the problem is that the "motion tile" effect is seeing the "whole" pixel dimension of the video that also includes the alpha channel and is applying itself to the whole frame instead of just the opaque area (the actual stabilized video). Because of that the motion tile effect is tiling the whole frame, including the alpha of it which leaves transparent gaps between the two tiles.
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Hi all
Got a job where I want to use alpha channels to cut-out some images in Photoshop and then put them into an ID frame with a black background. Want to use alpha channels rather than a clipping path as I need the edges to be feathered (have applied 2 pixels of feathering to the selection in Photoshop before saving it).
When I do this and drop it into Quark it looks good but when these images are dropped into ID and then the alpha channel is turned on, with the default Threshold and Tolerance settings, it doesn't look good. It looks like a rough approximation of my alpha channel, all the fiddly bits and bezier curves in the selection have been smoothed out and the feathering has gone. Playing with the settings doesn't really seems to help either. If I turn on the alpha channel in the import options when importing then it comes in as expected but I have quite a few images already in the document that I need to turn on the alpha channels for.
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thanks,
Iain

Thanks for your reply Bob. I've confused things with my terminology I think. We're drawing a path round the image, using bezier curves where appropriate, making that work path a selection (feathering the edge in the process) and then saving the selection (as an alpha channel) and then using the feathered alpha channel in Quark/ID to knock-out the background. Not keen on using a PSD with a transparent background at the moment as these are just test files while we show the customer what it will look like if we do cut-outs. We are making a couple of different alpha channels per image, with different settings, which would mean multiple files if we used your method I think. Maybe once we get the approval from the customer we could use PSDs as you describe but I was just wondering why the options for affecting alpha channels after importing the image aren't working as I expected.
Iain

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For more information, see these sections of After Effects Help on the Web:
"About alpha channels and mattes"
"Alpha channel interpretation: premultiplied or straight"
"Output module settings"

Keys in CS-5 - Save Alpha Channel AVI

Hello. I go shoot keys with green screen. On Location is good for some of that, but I have to remember to adjust the sound level next time. To show kids who did the scripts, I used the CS3 Ultra to quick ket a sample and dump on a background like we plan to use.
When I get into Premiere CS-5 I want to pick the take I like, trim the ends, key to transparent and save as an AVI with alpha channel. Liked the Ultra keyer when it was separate, but not sure about CS5 one, as controls were better organized in the CS3 version **.
1) Do I need to set up a line on timeline as alpha channel, in order to save same? If so which one? These are just keyed person with clear BK.
2) Please help me with the settings so someone who makes the final steps, I think in another program, can open up the AVI files and have a good key to finish off. So far I haven't found one that will let me tick alpha channel to save.
**Yes i should find the Premiere fix list and ask for an ULTRA pop up of the CS3 design, if they are going to keep in Premiere.
3 PS) Does Adobe have a set of books for the CS5 programs? When i got CS3 they offered me a deal to take the books. Saved me many times to be able to flip pages to find answers. Even a PDF of same might speed things along.

Look here for the steps to export an AVI with alpha: exporting video with an alpha channel (transparency)
I don't think you'll ever see Ultra as a standalone program again, as it's now integrated into Premiere Pro as an effect. I never used Ultra CS3, as I thought it was too rinky-dink, but the CS5 version is quite nice and easy-to-use (and get a great key) in most instances. It's not bulletproof, but Keylight in AE takes care of the more troublesome keys.
You can download a PDF of the help document for a particular application by going to the online version of the help docs, and clicking the PDF link in the upper-right corner. You can get Premiere Pro CS5's PDF right here: Adobe Premiere Pro CS5
You should also have the Community Help application installed along with the CS5 suite. If it doesn't open when you hit F1 within your app of choice, it should be available in the suite's application folder. It works well, and the help is updated frequently.

I want to export with alpha channel using a codec that carries less data than gopro cineform

Hi--I want to export some intermediate files with an alpha channel. i'm using gopro cineform, and these files end up being so large, meaning that i have to sit through hour long renders. is there a a codec i can use that has an alpha chanel but creates a smaller file size?
thanks

Thanks for your help Patrick. I tell ya, I can't believe what's going on. As I said, this project until today has not caused me any issues what-so-ever. The other six sessions are totally fine. I also created a quick project with the same settings added text - then exported using the same settings I've used before, and it exports with the proper alpha channel.
Yet, I rebooted the Mac, made sure to delete old versions in the trash can and everything. Still, no alpha.
To keep moving forward, I literally had to use a color key in FCP to cut out the background color.
Crazy!

Create Photoshop stil with alpha channel?

I'm using dvMatte Pro3 to strip out the green screen.
I'd like to be able to generate a Photoshop CS4 file with the alpha channel, so that I could composite the background in Photoshop, but I haven't been able to get that to work.
Is there a way to do this, or do I generate a matte along with the still and layer them in Photoshop?
BTW - I've also had a bit of trouble directly taking a sequence of a freeze frame out to a Photoshop CS4 file. It creates one using 'Export using Quicktime Converstion', but it is only 100k and not a valid Photoshop file.
I've had to create a new freeze frame from the sequence (with my background rendered into the shot), and then export this freeze frame (not the sequence) using 'Export using Quicktime Converstion' to get a workable Photoshop file.
Always interested in a better method?

Les Caudle wrote:
However, I'm not getting a PSD with the background as an alpha channel.
You won't. The foreground contains the alpha channel. The background is what appears behind the alpha channel
Here's what I've done.
1. Strip out background in FCP7 with dvMatte Pro. The sequence contains a single freeze frame I wanted to output to Photoshop.
I am assuming your clip is a person standing in front of a green screen and you have keyed out the green. That leaves an alpha channel in the shape of your person.
2. Render sequence.
this is probably the mistake you are making although FCP6 and 7 were said to have fixed the export issue. You are attempting to export a rendered sequence. The matte has been filled so there is no longer an alpha channel.
3. As I've been unable to export the sequence to Photoshop (just creates a 100k file that is not a PSD), I take a freeze frame of my render.
I still don't know what this means; telling me the same thing twice is not an explanation so I will disregard is irrelevant.
4. I select this 'freeze frame' and Export using Quicktime Converstion, set the type to image, set it to Photoshop and to Millions+.
All you are doing is exporting a full frame of video. It has no alpha channel. but even if you separated the two video layers, your background plate still has no alpha channel that contains any valid information. It will appear completely solid white if you viewed it using the alpha button in the Canvas.
5. The resulting PSD has the background stripped out, but it is black, not transparent. So, I'm obviously doing something wrong?
Possibly the 'freeze frame' I create is not in 'millions+' - so when it is exported there is no alpha?
I'm totally lost now, why do you care about the foreground? I thought you wanted the background with an alpha? Are you looking at the alpha-only view in Photoshop?
I take full responsibility and apologize for not being able to see through any translation errors that are creeping into our discussion. Like most Americans, I only know English (and enough Spanish to be able stay out of trouble at a Mexican restaurant).
bogiesan

Keying with an alpha channel

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