Clean Alpha Channel for use in video

[garrettc]

Ok, this is a problem that has perplexed me since the beginning of my editing career:
How do you create a 32 bit .tga file in PS with semi transparent objects and/or drop shadows, that will display cleanly in Premiere? (e.g., text with drop shadows at 50%)
I usually just end up bringing in a PS document, which displays objects at any level of tranparency on the timeline with perfect, clean drop shadows.
The thing is, PS files must be rendered and my hardware supports 32 bit .tga files in realtime.
Here's what I've tried:
In PS, Ill type out some text and add a drop shadow with, say 50% opacity.
Next Ill click on the effect and select "create layer" to place the shadow on its own layer. Then Ill CTRL + SHIFT click both the text and the shadow layer to select both and then create an alpha channel in the channel palette, then flatten and save as a 32 bit .tga.
So, when I import the file into Premiere and place it on a track(above V1) I then go to transparency options, and choose alpha channel. The file displays in realtime over the video, but the shadow has become gray and opaque...the transparency is gone. I've also tried selecting white alpha matte with the same results.
Where am I going wrong? Is it somewhere that in PS or Premiere that I'm screwing up? There has to be a way to do this, because I get single frame exported .tga files from animators that have glows, shadows, etc. all preserved perfectly on the timeline.
Thanks a million in advance to ANYONE who has the answer.

[Robb Barrett]

Forgive me for not knowing Premier fully, but I may know why it's doing this. I think it may have to do with your layer flattening.

An alpha channel is a specified color that is regarded as teansparent. That it to say that it should be decoded as transparent.

The problem is that in a drop shadow, you're dealing dealing with grays, not black and white. The software might say that color #000000 is alpha, and the editing software then looks in the file for everything that is #000000 and makes it zero.

Since you've flattened your files, it's even less black and white than before. Transparency is a very difficult function for most computers to handle, and a good looking drop shadow is next to impossible.

It's very much like a chromakey. The legendary greenscreen is used because human skin has no green pigment in it which would cause dithered transparency.

Your best bet would be to post this question on the Premier board. Someone there may be able to help you.

[Chris Cox]

Robb - no.

And alpha channel is an additional CHANNEL in the image data.

It has nothing to do with a specified color.

And alpha channels are not necessarily the same thing as transparency. They're just extra channels.

Transparency is just one use of an alpha channel.