removing blue screen on imported footage

Hello,
Anyone one out there got a way of making an alpha channel out of a
blue screen footage file.
I have some good footage of a girl with a blue screen backing but when
I go in to remove it, I don't know how, or the way I do know of isn't
working.
Any suggestions please??????
or links to tutorials, or what it is called in the after effects guide.
Thanks so much.

 

Define what YOU mean by "remove"? Typically, chroma-key
screens are used to *substitute* a different image (even if it is
just black). Do you not have software that will do chroma-key?

 

I want to export the clips I have with the blue screen background, so
that it only contains that image, so "remove" in my terms, means take
out that blue screen background so that the exported movie now is in an
alpha form, much like if I masked it though this was filmed in a blue
screen environment, so I thought I could simply export without the
background, but I don't know how.
So any help! would be much appreciated.
Thanks for your reply.
I look forward to your advice.
chroma-key is that where you select which colors can be taken out?

 

"wgash" wrote ...

Is that even possible? Is there a movie format that includes
an alpha channel? The whole concept of the blue or green
screen is that it is as close as they could get to an "alpha"
channel.

You still haven't mentioned what software you are using.

 

The whole concept of the blue or green

Exactly, so how do I make the alpha channell when i have a blue screen
clip? I did the interprit footage thing and it won't let me, so I am
wondering if it is because i didn't import it correctly or something.
as far as software goes, I am using after effects, and I used chroma
key hue/ sat, color balance etc... to select the color to take out but
it won't do it all, and it takes the blues out of the part of the clip
I want to save.

here's a link to the file I am working on.
http://zoopopula.com/Mooshu
it is still rough and everything is done with masks but I shouldn't
have to do that. as far as software again I am a novice so I may not be
following you my apologies.
thanks again for your reply.

 

There is no "alpha channel" in any video file format I have ever
encountered. You didn't mention which file format/codec you
are using. In our grandparent's era, Hollywood used "blue-screen"
and in our parent's era, television used "green-screen" as a crude
attempt at an "alpha channel" The really high-budget productions
had "traveling mattes" HAND-PAINTED for EACH FRAME
of film/video.

Chroma keying is a very demanding technique that requires extremely
"clean" video. If you are using any kind of compressed video codec
(even DV), it is generally considered to be not really good enough for
quality chroma-keying. And the more compressed formats like MPEG,
etc. are likely too "noisy" to even bother with. Better/easier to make a
"traveling mat" (painted frame-by-frame) than to try to do chroma key
on MPEG footage.

Some people get reasonably good chroma-key from DV when they
use green (rather than blue) because you have roughly twice the
resolution of the green channel than you do of blue or red. But then
they also have to be extrememly careful about maintaining very even
lighting and keeping contrasting colors, avoiding key color reflecting
back on to the subject, etc. etc. etc. You can likely find a lot of
discussion by spending a few quality milliseconds with Google
searching for DV and chroma-key. (Assuming you are using DV.
If you are using MPEG, all bets are off.)

With so much compression, it is hard to tell where you tried to
do chroma-key (both technical and artistic compression , i.e.
"impressionism", or maybe we can't distinguish between them at
this end of the wire? You might have to verbally explain what
we are seeing and/or limit the clip to just the problematic chroma-
key section.

 

When overlaying a blue screen onto video good results can be obtained using
the following in Adobe Premiere. Place the blue screen clip on Video 2 or
above. Right click on the clip and choose Video Options/Transparency. In the
next dialog select Blue Screen from the drop down. Should you still detect
blue on the edges set the Tolerance level until you are satisfied.

In MediaStudio place the clips in the same manner. Right click the blue
screen clip and select Overlay Options. From the drop down select Chroma
Key. Etc, etc. In Vegas it's not much different.

--
Larry Johnson
Digital Video Solutions

http://www.digitalvideosolutions.com
877-227-6281 Toll Free Sales Assistance
386-672-1941 Customer Service
386-672-1907 Technical Support
386-676-1515 Fax

 

I think what Richard is asking is, why do you want to do this?
What do you expect to see where the blue is now? it can't be nothing;
that's not possible. There is no "nothing" in video. The closest
you'll get is black, but black isn't "nothing".

 

I got good results from converting a blue backed figure into an animated
gif. Its useful if you have a loop you want to move around a screen (like a
bird). The gif with its alpha channel allowed for a better real-time
preview then chroma did. A quick and dirty way of adding animation w/o
exporting.

But re-reading your question I get the impression you just want your basic
chroma-key. If your editor doesn't have a 'chroma key' feature then you
need an editor that does. If your looking for a freebie I believe the 3D
program blender has a chroma key feature in its video editor
(www.blender3d.org) however expect to spend an evening or three in a blender
forum learning how to operate it. But not a bad program to know.

 

Thanks...
What do you mean change g to a?

 

wow!
you really know your business, that's really cool.
thanks for your help.
I will go spend more milliseconds looking this up.

 

Using an animated GIF is only good if you are working in 256 colors. Not
good for 24bit video.

 

If you look at the headers in a newsgroup post, you'll see en email
address for the poster.
I've set mine as , but that's not my real address.
"change g to a" is what you need to do to get my real email address.
This is done to fool email harvesting software, and when something
like this is in a signature, it's understood that is is a way to get
the real email address.

 

AH! thanks, I am totally new to groups so, I don't have much idea how
they work, thanks.
Shane.

 

Check out Serious Magic Ultra. It does a very good job with chroma key on
DV.