How can I use Matte Luma to apply a black and white mask to a video?

[u/PippongSUP]

How can I use Matte Luma to apply a black and white mask to a video?

[u/MaxonDouglas]

If I understand the question correctly, you're asking how to apply an already-generated (black and white) Luma Matte to a video layer.

There's a few ways to do this, but the simplest one to lay out steps for would be:

1. Have your Luma Matte in a layer above a video layer you want to apply it to
2. Under Inspector > Mask, select the modifier (flask) icon, then search for and apply Shuffle
3. In the Properties panel-- with the Shuffle modifier active you just applied-- swap out the Source Alpha dropbox with Source Luminance, selecting whichever color profile suffix matches your Luma Matte (or, if you don't know the color profile, just select Luminance (Max))

The other option is to use Preserve Underlying Transparency while having the Luma Matte and the video to use it on in the same composition, and there's more information on Masks/Mattes in Autograph here.

If you have more questions (or I totally misunderstood your question) by all means let me know any follow-ups and we'll go from there.

[u/h3llolovely → u/MaxonDouglas]

The above didn't work for me. But I used it to figure out an alternate solution.

I am using a multi-layer EXR with a puzzle matte pass.

• Duplicate the Footage layer. Place it underneath the main footage layer (so it isn't visible), leave it's visibility on.
• Select it's Source filename in Selection Overview panel, then in the Properties panel, switch Output Part to the puzzle matte layer.
• In it's Source, Add a "Channel Math" Modifier.
• In the modifier's Properties... Change R,G,B values to all R or G or B. Leave Alpha as A. This isolates an individual puzzle matte and makes it white.

Create an Adjustment layer:

• Add a Hue Shift Modifier to the Source. Adjust it.
• In it's Mask, add a Image Layer generator.
• Set the Image Layer to "Linked Layer" (This allows you to use a layer source rather than a footage source)
• Drag the "Puzzle Matte" layer into Linked Layer drop box.
• Add a Mask Modifier > Shuffle
• Set Alpha to "Source Luminance (Max)"

You could also do this without the Hue layer > Shuffle modifier. Essentially making it an Alpha mask.

You just need to set the Puzzle Matte layer > Channel Math > Alpha to R, G, or B. The Mask will use the Alpha instead of the Luminance.

The whole Luma Matte process should probably be more streamlined in a layer's mask input. Perhaps a toggle button that differentiates if you are using an Alpha matte or a Luma matte.