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alpha channel problem
hello,
I’ve got a moving video (graphic) on V1, and it’s alpha channel on V2.
I of course put the Matte Key on V2 and “invert key.”
When I play it back everything seems to work EXCEPT
that there is a slight shadow in the movement. In other words,
the black is not totally transparent … it is somewhat non-opaque.
I”ve got the basics right, but something is causing this shaddow,
this non-opacity. Does anyone know?
Thank you for any help.
Jack -
8 Replies
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It’s not in your matte?
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Grin, thanks for the reply.
In what way could the problem be with my matte?
It is a straight-forward black & white image,
the alpha of the RGB image below it on V1.What sort of problem is it possible to
have on the matte? Maybe you are right,
but what would I be looking for?
Thanks for your help. -
The only thing I can think of that could be the problem with
the Matte is that it has been dubbed down a couple of generations.
It was created on Avid, then outputted to a DVCPro tape,
then dubbed one last time to another DVCpro tape. Two generations.
Can THAT be the reason my Matte Key effect is a bit non-opaque?
In other words, i see a hint of gray as through the movement effec.
Thank you. -
It’s not a generation problem.
I made a new moving graphic matte, from scratch.
Placed it on V3 over V2 where I have the same graph in RGB.
V1 has background video, that i want to see under the movement.
But when I scale down the alpha matte and RGB mattes,
in the movement the alpha matte is not totally transparent.
You can see a slight shadow in the movement. No transparency.Can someone please help? What’s wrong?
Thank you for any advice -
It’s so hard to say, not being able to see it.
Since you created a matte from scratch, can ya just create a new grafik with an alpha channel?
it may be quicker than trouble shooting. -
Jack
Has the alpha got soft edges? in which case a pre-multiplied alpha could pull a dull/blackish halo around the alpha edges in the AVID. Don’t know why the AVID can’t treat a pre-multiplied alpha the way its intended but it really is something they should fix!!!
Have you tried taking the matte and footage into After Effects or another similar compositing package and tried the same again. Generally these programmes deal with alphas and mattes far better than the AVID can.
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I have had slight transparency problems with mattes if My black was not set at 0,0,0 and my white was not set at 255,255,255. I fit is not pure white or pure black than it will have some amount of transparency/opaqueness.
Double check the matte with a color picker and see if the white and black are as above.
David Oulashian
Editor, E! News -
[David Oulashian] “I have had slight transparency problems with mattes if My black was not set at 0,0,0 and my white was not set at 255,255,255. I fit is not pure white or pure black than it will have some amount of transparency/opaqueness. “
Step into the matte key. Apply a Color Effect to the matte, and increase the contrast. See if that helps
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