Using the Difference Matte in Premiere Elements

[William Todd6C1B]

Could someone provide me guidance on how to use the Difference Matte effect?  I can't quite figure out the correct way to layer the source, static background and destination background video tracks, which track(s) the Difference Matte effect shoud be applied to, and what should be designated as the Differnce Layer for each track (if applicable).  Thanks!

[Steve Grisetti]

What effect are you trying to create? Can you link to a video of this effect? 

[William Todd6C1B]

Hi Steve,

Thanks for your help!  I am trying to create an effect where a person on the source video passes in front of an actor that I have superimposed into the same scene.  I have synced the following three videos on my timeline:

- Source Video:  This is a locked-off image of a stage that I shot from a tripod.  There is no camera movement but the image is a bit dark.  I framed this shot to leave an empty space where I could green-screen in another actor, but on this track the green screen actor is not present.  At one point, an actor on stage moves from one side of the frame to the other, passing over the spot where the green-screen actor will be present for about a half-second.  

-  Static Background:  This is a frame-grab I took from the Source Video.  In this frame grab, the area where the green screen actor will be placed is empty.

- Destination Background:  This is a separately rendered version of the Source Video that contains the other actor I have green-screened into the empty space described above.  In this track, the stage actor currently moves behind the green screen actor.

I want to use the difference matte to "pull out" the moving stage actor and superimpose her over the green screen actor.  Ideally I'd like to render out a complete replacement shot, but if the difference matte contains a lot of artifacts I can use editing, cropping and garbage mattes to extract just the section where the actors actually intersect, lay that over the Destination Background and re-render the scene.

So, with all that being said, I don't know the right way to layer my video in the timeline, which tracks to apply the difference matte effect to, and how to set up the difference matte for each appropriate track.

Thanks again!

[Steve Grisetti]

I don't know of any way to do this in Premiere Elements, William. 

[William Todd6C1B]

Elements does include a Difference Matte effect which should do this, but the online documentation doesn't describe how to set it up.

[Bill Sprague]

I had no idea that effect existed.  I googled for 'difference matte effect' and got several hits and tutorials on how it works in Adobe After Effects and Premiere Pro.   There may be enough similarities that it will help you figure it out.   It appears that you put one clip above the other and apply the effect to the top (or maybe bottom) clip.   

[William Todd6C1B · Accepted solution]

OK, after much trial and error, I finally got this to work.  This is how I layered the tracks in Premiere Elements 19:

Video Track 1 - Static Background image (freeze frame from the source video or other clean background plate).  This corresponds to "B. Background Image" in the Adobe illustration.  Do NOT apply a Difference Matte effect to this layer.

Video Track 2 - Destination Video (the video background you want to use for the moving image pulled from Video Track 3).  This corresponds to "C. Image on the Second Track" in the Adobe description.  In my project, it's the video where I put the green screen actor.   Do NOT apply a Difference Matte effect to this layer.

Video Track 3 - Source Video with the moving element you want to pull out (in my case, the moving stage actor).  In the Adobe description above, this corresponds to "A. Original Image".  Apply the Difference Matte effect to this track, and select VIDEO 1 as the difference layer.  Use the sliders to adjust the keying to the desired level (Matching Tolerance seems to make gross adjustments, while Matching Softness reduces the outline around matte but may also increase transparancy.  Not sure what Blur Before Difference is supposed to do.)  

Overall, I was pleased with the final composite.  There was some bleed-thru and edging on the matte, but the lighting conditions in my project were really poor (it was shot in a theatre) and I'm sure affected things a bit.  A pretty powerful effect for a piece of consumer software!