Can't get Image Matte Key to work in PP CS6 Mac

Hi,

After tearing my hair and muttering adult phrases for a couple of hours while following the below instructions from the PP CS6 pdf manual, I still can't get anything but a black screen when trying to apply the Image Matte Key to a simple set-up. The project is in HD 1080p50 format and the basic editing has been largely problem free.

1. Add the clip (used as a background) to a video track in a Timeline panel.
2. Add the clip you want to superimpose to any track higher than the track containing the background clip. This is the clip revealed by the track matte.

   Be sure the superimposed clip overlaps the background clip in a Timeline panel.

3. In the Effects panel, click the triangle to expand the Video Effects bin and then click the triangle to expand the Keying bin.
4. Drag the Image Matte Key to the superimposed clip in a Timeline panel.
5. In a Timeline panel, select the superimposed clip.
6. In the Effect Controls panel, click the triangle to expand the Image Matte Key settings.
7. Click the Setup button , browse to the image being used as the matte, and then click Open to select the image.
8. (Optional) If you’re animating the Image Matte Key over time, make sure that the current-time indicator is in the position you want. Click the Toggle Animation icons for the settings you adjust.
9. Click the Composite Using menu and choose one of the following:
   Matte Alpha Composites the clips using the alpha channel values of the image matte you selected in step 7.

   Matte Luma Composites the clips using the luminance values of the image matte you selected in step 7.

What I do is:

• I have a clip on Video 1. I want to use a hand painted luma matte made in PS CS6 for changing levels ('exposure') in an irregular area of the clip.

• So,  I duplicate the clip on Video 2 and add an 'RGB Curves' fx for the level adjustment.

• Then, I add the Image Matte Key to the Video 2 clip and set up the Photoshop b/w image (RGB 8 bit, 1920x1080) from my external eSATA disk containing the Project and media (step 7 above).

• I select 'Matte Luma' (step 9) – and expect the relevant part (painted white on the matte .psd pic) of the duplicated, level adjusted clip to be superimposed on the Video 1 clip.

• But I only get BLACK!

I tried using Track Matte Key, with the matte pic on Video 3 – no problem, worked just as expected.

So, what's the voodoo with Image Matte Key?

Kind regards,

Joachim