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Need explanation of Alpha Channel Options within SVP
I got my alpha channel question answered and it’s now working.
Thanks.
A question I now have is: when you click on the properties of an element, within the Media tab, you have the option to set your Alpha Channel.
What is the difference between the different settings (ie, Undefined, Straight (unmatted), Premultiplied, Premultiplied (dirty)), and in which situations would you select each of these?
Thank you.
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2 Replies
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In a brief nutshell the straight unmatted and
premultiplied are the two most important ones. Basically,
there is no hard or fast rules where either is concerned, because most
of the time it will depend on your perception as to which of the
two gives you a cleaner matte when selected (however premultipled
are normally cleaner), and this is due to how the media was
originally processed.Steve Rhoden
(Cow Leader)
Film Editor & Compositor.
Filmex Creative Media.
1-876-832-4956 -
[Ron Whitaker] “What is the difference between the different settings (ie, Undefined, Straight (unmatted), Premultiplied, Premultiplied (dirty)), and in which situations would you select each of these?”
As Steve said, you need to match the alpha channel to the way the original was processed. Most alpha channels like those in PNG files are straight(unmatted). Sometimes when working with particles in a 3D program, using an alpha that is premultiplied with black with help the small particles stand out better. In this case, you can tell Vegas that you premultiplied the alpha and it will adjust for it. The thing to remember is that you should match the alpha processing with the original footage alpha processing.
~jr
http://www.johnrofrano.com
http://www.vasst.com
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