Can Vegas shrink matte in chromakey?

RoyBU wrote on 12/5/2005, 7:52 AM
I am working with some very poor blue screen footage, which has taught me much about chromakeying in Vegas. I have also tried the demos of Ultra 2, Boris Red & FX and After Effects. All of these demos have a feature which allows me to shrink the matte, or mask, that the chroma key produces. This is very handy in eliminating most of the spill or "halo" effect around the actors that remains after applying the chroma key effect. But after working with all these products, I find that the Vegas chromakey is as effective and more convenient (well, maybe Boris Red beats it) EXCEPT that I can't see any way to shrink the matte. Is there some way I am missing?


Spot|DSE wrote on 12/5/2005, 8:33 AM
You have to create a garbage matte if you want to shrink the matte, and that's about the only way that I'm aware of. Maybe someone else has a different technique. I'll often apply a .003 blur on the garbage matte in addition to shrinking it.
It would certainly be great if Vegas had this as an option though.
RoyBU wrote on 12/5/2005, 10:31 AM
Thanks for the reply, but I'm afraid I'm not sure to what you refer. (This is a problem I have with the Vegas help system -- there's no way to look up words like "garbage" or "matte" and find anything.) Do you mean creating a mask in the pan/crop tool? Or something else? Could you please direct me to the specific command? As I'm sure is obvious, I'm a relatively new user. Thanks.
Spot|DSE wrote on 12/5/2005, 11:15 AM
You set up the chromakey like you normally would
Then in the Chromakey tool, you check the "Show Mask Only box" and set this up so it's as much black/white as you can get it. Render that out as a new track without audio.
On the new track, you'll apply the levels filter so you have ONLY black and white, and put the track in Mask compositing mode. Make it a parent to the chromakey footage beneath. Now you can remove the chromakey filter from the footage beneath, as the matte/mask track you've created is what passes the footage.
You can add blur, shrink, whatever you want to the mask track.
If you have the Vegas 4, 5, or 6 Editing Workshop books, this is found in the book.
"Garbage Matte" is an industry term, but I don't know of any software that actually uses the terminology? Hence why you won't find it in the Vegas owners manual. It's also a last ditch trick for NLE's these days.
p@mast3rs wrote on 12/5/2005, 12:00 PM
I think Premiere Pro is the only NLE that I have ever seen use the term garbage matte.
RoyBU wrote on 12/5/2005, 7:54 PM
Thanks very much for the step-by-step explanation. I think that will really help my project. And no, I don't have the Editing Workshop books; I will look into that as well.
GGman wrote on 12/5/2005, 8:56 PM

I do it without rendering. Just apply a chromakey, then apply a Gaussian Blur to the same event and uncheck RGB so only alpha is used in the blur.

Spot|DSE wrote on 12/5/2005, 9:10 PM
Gary G, you always have fun tips. You need to show up more often.
I render, but that's out of habit...and remember in the past (when the habit came about) it was SO slow on most machines. Of course you're right, we don't need to render.
Stonefield wrote on 12/6/2005, 12:58 AM
......Just apply a chromakey, then apply a Gaussian Blur to the same event and uncheck RGB so only alpha is used in the blur.....

Wow, what an amazing and very timely tip.......I'm workin with some green screen now ( RIGHT now actually ) and I'm having some fun playing with that idea.....

thanks GGman ( Good Game !!! )

Grazie wrote on 12/6/2005, 1:35 AM
GGman! Kept! Superb! . . simple and straightforward too. - Grazie
farss wrote on 12/6/2005, 2:49 AM
Sorry if this tip sounds condescending but I've had to explain this so many times.
The screen only needs to be a bit bigger than what you're trying to key IN, it doesn't need to be as big as what you're trying to key out. One can very easily mask the rest of the frame out in any NLE.

I only make this point because a number of times people have asked for a screen X x Y metres yet all they're keying is a talking head 1/4 of the size of the screen. They're all set to pay serious money for a studio with a HUGE CK screen just for one talking head.

To go a bit further, all that really matters is the few pixels around the subject, the rest can be manually fixed by taking the matte that DSE detailed how to create into PS or using anyone of a number of the Vegas tools to mask the rest of the frame. Of course if there's a lot of motion then it can be tedious.

robertglotzbach wrote on 1/16/2006, 4:54 AM
Hello All,

Maybe I'm asking for the obvious, but I did many searches and cannot find the answer.

I am strugling with a chroma key set-up; experimenting in both Vegas and After effects.
So far it looks promising in Vegas, but I cannot get rid of the "spill" around the edges.
My first question is: How do Shrink the matte in Vegas?
My second question is: Will I be better off in After Effects 6.5 Standart (maybe I should upgrade to PB)?

I don't have the Editing Workshop books.

Thanks for you help.

Kind regards: Robert
logiquem wrote on 1/16/2006, 6:07 AM
I my experience you *must* use the chromablur fx (before chromakey fx) to get a very good key in Vegas. Try it. It is a CPU intensive fx, but indispensable IMO.
robertglotzbach wrote on 1/16/2006, 6:25 AM
Hello Logiquem,

Yes, I am doing it the way its described above, so with using chromablur.
The point is that I need to shrink the matte in order to get rid of the edges and I don't know how.
Any idea?

Thanks for your answer.

Regards, Robert
robertglotzbach wrote on 1/17/2006, 4:48 AM
OK, I bought the book (Vegas 5 editing workshop) this morning, looks very good.
But,........... the example file that I thought would help me (badscreen.veg) seems to be missing on the disk. Any sugestions?

Thank you, Robert G