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Convert Matte into Alpha Channel???

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Dudley Saunders
Convert Matte into Alpha Channel???
on Oct 8, 2008 at 6:29:43 pm

Is this possible? Because of our station's antiquated keying system, I have to take a frame of a video lower-third and ultimately give them a Targa with alpha channel to air over a program.

The problem is that the video lower-third has some transparency, so it's best if I can use the original matte as my alpha channel -- otherwise, if I create my own in Photoshop, the transparency reads as black.

Is there a way to bring in the original matte and convert it into the alpha channel in Photoshop? I keep hunting around and can't find a way to do this. Any ideas?



Dudley Saunders
Editor-Producer


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Michael Rothenberg
Re: Convert Matte into Alpha Channel???
on Oct 8, 2008 at 10:11:41 pm

I would think you would do this the same way you'd make a regular alpha channel. Make a selection, then switch over to the Channels palette and click on the "make channel from selection" button at the bottom.

To make the selection, though, you have to help Photoshop "see" the grayscale in the video grab.

1. Bring the matte into Photoshop the same way you did with the other frame grab.

2. Shift-drag to add the matte to your file in the same place.

3. Select the layer, then go to Select>Color Range and play with the fuzziness until you have a selection that approximates the transparency of your matte.

Once you've made the alpha channel and are satisfied with it you don't need the matte layer anymore.

Hope this helps - hope it works!


Michael Rothenberg
Peak Productions


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Del Holford
Re: Convert Matte into Alpha Channel???
on Oct 13, 2008 at 7:55:10 pm

For a few dollars you can buy Tools for Television Pro from Glen Stephens and it will plug in to Photoshop and create alpha channels from the original. This will automatically make transparent alphas from the original. I use TFT Pro almost every day and it's a money and timesaver. If you want to add more transparency go to Channels, turn off the RGB channels and work on the alpha channel in black and white to turn the white towards gray in whatever areas you select with the wand or marquis tools. I use the ramp tool to go from white to black for transparent rectangles etc. You can also airbrush areas with gray to add transparency.

Del
fire*, smoke*, photoshopCS3
Charlotte Public Television
del underscore edits at wtvi dot org


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Richard Harrington
Re: Convert Matte into Alpha Channel???
on Oct 14, 2008 at 3:33:45 am

Whats wrong with just copying the content of the mask... then adding an alpha channel, select it, and paste pixels into it.

Richard M. Harrington, PMP

Author: Photoshop for Video, Understanding Adobe Photoshop, and ATS:iWork


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Del Holford
Re: Convert Matte into Alpha Channel???
on Oct 14, 2008 at 12:47:16 pm

Not a thing. I did it that way for several years. I still on occasion make changes to improve the alpha channel. However, for multilayer comps TFT Pro saves time (therefore money) and for numerous lower third work it makes the process less tedious. I'm not paid by Glen to say this, nor do I get commission. Maybe I should.... :-)

Del
fire*, smoke*, photoshopCS3
Charlotte Public Television
del underscore edits at wtvi dot org


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