Chroma Key Not Working

Movick wrote on 4/26/2007, 6:17 PM
Hello,

I just did my first chroma shot with a green cotton fabric. The area was well lit, no wrinkles, and a tight shot. I dropped the footage into VV5 timeline and keyed the green. I lost some luminance in the subject, but overall its acceptable. The background around the subject is pure black, however I cannot see the video track below through the keyed black area. Can anyone tell me what I have done wrong, or if I need to set something.

Thanks!

Movick

Comments

Movick wrote on 4/26/2007, 7:21 PM
Anyone??????
TheHappyFriar wrote on 4/26/2007, 7:36 PM
Did you check to see if the track has the proper transparency settings (alpha, difference, etc)?
Movick wrote on 4/26/2007, 7:38 PM
Source alpha no?
goshep wrote on 4/26/2007, 7:47 PM
Are your tracks lined up on the timeline? Chroma track directly on top of background track? Is your chroma track accidentally set to solo? Those are the two things that jump out at me as possible problems.
Movick wrote on 4/26/2007, 7:55 PM
Set to source alpha, not solo. What the heck else could it be?????? I'm going nuts here. I have a clean mask why wouldn't this work?

Mov
Spot|DSE wrote on 4/26/2007, 8:01 PM
How do you know you have a clean mask if you're not seeing the media beneath?
Both tracks should be set to Source alpha, you need media beneath the keyed events/track.
Be sure you didn't accidentally insert a keyframe that has the masking turned on, with other keyframes with masking off.
Muted tracks, opacity set to zero, codec that Vegas can't read...
If you mute the keyed track, can you see the matte track?
Movick wrote on 4/26/2007, 8:01 PM
Here's a side by side of the chroma:

http://img87.imageshack.us/img87/4983/chromaoo2.jpg

Anyone help?
Movick wrote on 4/26/2007, 8:03 PM
I know the mask is clean in 2 ways: (1) When I show the mask in the chroma key window, I see it clearly. (2) When I set the transparency to add subtractive, etc, I get a clean blending of the 2 channels - no dreck from the keyed channel.
Movick wrote on 4/26/2007, 8:07 PM
Weird, when I set the transparency level of the keyed track to 99.6 I see the masked subject perfectly, although slightly transparent. Does this provide any clues?
Spot|DSE wrote on 4/26/2007, 8:36 PM
Yes, it suggests you've got the Chromakey tool disabled. Is there a check in the Chromakey tool tab in your FX chooser?
What other FX are on that that chain, if any?
What about settings in preview window? got your FX turned on?
Movick wrote on 4/26/2007, 8:51 PM
Turned on in video track. You lost me in the preview window though. Must I enable chroma key in the video output as well? Need I replicate the exact keyframes?
Movick wrote on 4/26/2007, 8:55 PM
I'm still confused. If I chroma out say a red background in a still shot with a blue circle in the middle, it shows through perfectly. Why does a video clip not do same in this program?
Spot|DSE wrote on 4/26/2007, 9:09 PM
I'm stumped. Unless you've got a codec problem, FX turned off in that timeline, or track in the wrong mode, don't have any more ideas.
If you have more than one keyframe in the Chromakey timeline, that's the first thing I'd look at (you mentioned keyframe*s*, which suggests plurality) to be sure that no keyframes are messing with your key.
Try replacing the media beneath the key with generated media, see if that shows up. If not, it points to a number of track or event-based options.
In your preview window, you've got a small button that is half dark/half light colored. Click the down-menu option in this button, and see if your FX are bypassed.
Beyond these suggestions, I'd try a RAM render to see if you've got some cached weirdness.
Movick wrote on 4/26/2007, 9:53 PM
Spot,

I think you were "spot-on" with the FX-bypass. Who knew! I believe this is the problem. Can't thank you enough amigo!!

cheers!!

Mov
Marco. wrote on 4/26/2007, 11:27 PM
Weird, when I set the transparency level of the keyed track to 99.6 I see the masked subject perfectly, although slightly transparent. Does this provide any clues?

Yes, this was a known bug in a certain Vegas version, probably right the version you use. If you are not on Vegas 5.0d - update to 5.0d. The bug was fixed in one of the further versions. If I am right - this not only affected the chroma key but any alpha properties used in events in a track. Reducing the track opacity just a little bit solved it.

Marco

Movick wrote on 4/27/2007, 1:50 PM
Weirder still,

After fiddling with the preview FX override setting, I had the same issue arise in another channel. The bug Marco referenced must be the cause, though I have already upgraded to the latest version of VV5.
As I was unhappy with the quality of the mask from Sony PD-150 footage in 4:3, I re-shot the green screen segment with an XL2 in 16:9. For some strange reason the XL2 footage did not suffer from the transparency issue as the 4:3 PD-150.

Just for the asking - I assume dedicated keying programs such as Serious Magic will provide a cleaner key than VV5? Although the final key I've created in VV5 is passable, I found I had to compromise quite a bit to get the end result, and it was not totally clean. I of course tweaked both the low and high threshold settings as well as the blur. Again the results are ok, not just what I would like to see. Any suggestions?

Thanks for all the help so far folks!

Mov
Marco. wrote on 4/27/2007, 2:54 PM
I just tested my version 5.0d. Chroma key works fine here. But maybe I was wrong with the version in which the bug appeared. I'm only sure about this bug existed and it must have been somewhere between version 5 and 6.

Any way to share your project file (without the media)? Maybe a closer look into it could help.

What almost always helps when chroma keying formats like dv is using the Chroma Blur filter before using the Chroma Keyer. Make an FX Chain. Chroma Blur first (find out best values), Chroma Key after.

Also in some cases I combine both Color Corrector Secondary with alpha function, instead of changing color a to color b - change color a to transparency (to abuse it as kind of a first Chroma Keyer) and use the regular Chroma Keyer after. Abusing the Color Corrector Secondary can easily key out main part of the colored background leaving only a small part colored (you can't do that with Chroma Keyer itself - it never leaves a colored part - just grey). Advantage is Color Corrector Secondary gives much more control. Then I use the regular Chroma Keyer to key out the rest. And again Chroma Blur should be used in first place.

You can even cascade Color Corrector Secondary as often as necessary what also can't be done with the regular Chroma Keyer. So even a very uneavenly colored background can be rather fine-tweaked this way.

Marco