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Alpha Channel Question
I posted this awhile back and wanted to respond further . . . .
I rendered to a photoshop sequence (just 1 frame it’s a simple graphic!), selected RGB+Alpha, clicking the alpha button I see an all black background (alpha channel).
After rendering, when pulled into Sony Vegas – insuring alpha channel is set to black/premultiplied – it doesn’t work – background is black.
When pulled into photoshop – background is black not transparent.
I changed NOTHING and rendered to quicktime animation (for the hell of it)
and THAT works.what gives? How do I get the alpha channel to work for a photoshop sequence?
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5 Replies
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I just made a text layer in a comp, then rendered using “composition>save frame as>file” with the “photoshop 32-bit” output module preset in AE 6.5. I reimported the image into AE and saw a transparent BG, no problem.
-RGB+alpha
-Millions of colours+
-PremultipliedDoes Vegas accept premultiplied alpha ? Maybe it likes straight alpha.
Steve
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yeah pulling BACK into After Effects works – however – doesn’t work in other applications.
Vegas DOES accept premultiplied alpha channel – as I stated rendering to RGB+Alpha Quicktime works when pulled into Vegas.
Photoshop is another story – if rendered to photoshop w/Alpha without changing anything from Quicktime working yield a photoshop file which will not have it’s alpha channel recognized in Vegas – heck if I pull it into Photoshop the background is black . . . . .
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Have you tried rendering to TGA? Make sure you have “32-bit” checked in the TGA “options” button.
Steve
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I have found that rendering a .PNG works best in Vegas. I had similar issues but was able to pull something off successfully with a .PNG.
My two cents…
Seth
wordtoyomutha
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Interesting — I just watched the Total Training section on Rotoscoping (which is AWESOME) and this was the exact subject they covered at the very end…
Basically, Adobe RGB+Alpha may not be compatible with other systems/programs; so, to get around this issue (or whenever passing your work off to someone else), you (may) need to make a Roto Matte.
Rotoscope your image out -> fill the image layer with white so that the masked out portion is black and your image is completely white. Export the comp (or frame in your case).
Then, for Vegas, you would need to drag both the B&W (matte) image, along with the original image into your timeline and drop them on top of one another. Apply a lumi matte (key) to the B&W image which should be the exact dimensions of the original, allowing the parts of the original image that you wanted to pass through the matte.
This way, you can still maninupulate the new lumi matte, if necessary; whereas, if you export it all as one file, it may not work, and/or you may decide that the matte needs adjusted later on.
Hope that helps.
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