Garbage Mattes

Posted on by Larry

[ This article was first published in the June, 2004, issue of
Larry’s Monthly Final Cut Studio Newsletter. Click here to subscribe. Updated Mar. 2007. ]

NOTE: This article was written using Final  Cut Pro 4HD. However, the concepts it covers – background plates and masking – apply to every version of Final Cut and Premiere, even if the interface changes from one version of the software to the next.

Christian Fessel sent me some stills from a recent project (“Girl From Alaska,” by the indie band SloMo, shot in DV PAL) where he was Lighting Cameraman (Director of Photography to us folks in the US) and editor. These stills were such a perfect example of how to use a garbage matte that I asked Chris for permission to share them with you.

The shoot took place in a bar in Sheffield, England. Chris wanted to set a moody, dark look, using wide shots while still seeing the singer. (I’ve lightened these images a little to make them easier to see on a computer monitor.)

First he took a wide shot of the scene using just set lighting.

Then, he added in all the lights and equipment for the singer, which totally trashed the wide shot; but did make the singer look great.

Then, he applied an eight-point garbage matte (Effects > Video filters > Matte > Eight-point Garbage Matte) to the video. The small numbers represent the eight control points where you can crop the picture.

Then, he opened the matte filter and clicked the little cross-hair icon next to each point, placed his cursor into the Canvas window, clicked and HELD the mouse down while dragging each point to crop the frame until all the video gear was outside the edges of the matte.

This the what it looked like before the points moved….

and this is what it looked like after all the points were moved to crop out the center of the background. If you were doing this, you’d see black on either the outside or inside of the matte, depending on how you were working.

And this is the resulting picture, a beautiful composite between the initial wide shot and the shot of the singer, with all the TV gear digitally removed.

Very nice and absolutely invisible.

UPDATE – Mar. 2007

Ayrod Seffak writes:

I have a question for which I can not find an answer. I have a footage with the boom mic showing at the top of the frame (present on about 2 seconds of PAL footage), I am trying to remove that boom in FCP but with no success. I thought I could send the clip frame by frame to Photoshop, erase the boom, then send the doctored frame back to FCP, but Photoshop does not do that on clips, it does it only on still frames.

 

Please, if you know of any other way to solve this problem, let me know.

Larry replies: There are many ways this can be done, using Final Cut, Motion, After Effects and a variety of other programs, but they rely on two things:

  1. That you have a piece of video where the mike is not showing that you can use to replace the portion of the video where the mike is in the shot. This video is called the “clean plate,” or “clean background plate.”
  2. That your camera is on a tripod so that both shots are steady.

UPDATE: Jeremy Traub writes in with another approach:

Ayrod Seffak asked about retouching individual frames in Photoshop. Here’s a way to do it with Photoshop, without the two limitations mentioned:

The easiest way to do this is to go though Adobe ImageReady, which comes with Photoshop. Just open the .mov file with ImageReady. Each frame of your movie will become a new layer. Now File > Save As… a PSD file and use the clone tool to your heart’s content in Photoshop. When finished in Photoshop, use Photoshop’s File > Scripts > Export Layers to Files. (You could also do everything in ImageReady, and use its File > Export > Layers as Files…) I recommend exporting as PNG files.

 

To avoid problems with gamma shift or lossy codecs, create the .mov file to be retouched as follows: from Final Cut Pro, Export Using QuickTime Conversion using the none-filtered PNG codec with no aspect ratio correction.

 

Incidentally, QuickTime Player can easily convert an image sequence back into a movie file (this requires QuickTime Pro, which comes with Final Cut Pro). From QuickTime Player, do File > Open Image Sequence…, then select your files (filenames must be less than 32 characters). Now File > Save As… and save as a reference movie.

Michael Grenadier adds the following caution:

You should almost never import an image sequence using this technique.The large number of files involved in an image sequence will seriously clog your FCP project (this is the voice of experience speaking). FCP will take a long time opening the project and in particular saving the project will be equally sluggish. It’s much smarter to use QuickTime to import an image sequence and save as a quicktime movie. By default, it will use the same compression as the image files so you can avoid any additional compression or you can do a save as any other codec normally available.

Larry replies: Jeremy and Michael, thanks for sending these in! Keep in mind that PNG is an 8-bit codec. This technique will work fine for 8-bit video, such as DV and DVCPro-50, but may show banding when working with 10-bit video.


Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *

Larry Recommends

Final Cut Pro X 10.4

FCPX Complete

Edit smarter with Larry’s brand-new webinars, all available in our store.

Access over 1,900 on-demand video editing courses. Become a member of our Video Training Library today!

JOIN NOW

Subscribe to Larry's FREE weekly newsletter and save 10%
on your first purchase.