When you do compositings of computer graphics or animations on camera footage which contains film grain or video noise you should add the same grain to the computer footage.

In the example I used a camera to create the grain source. Point the camera to a dark area. Then disable the automatic modus and set the gain to the amount where the campera produces the expected grain and record a few seconds. Then capture one second of this grainy footage into Final Cut.

The screenshot shows the grainy footage.

Add the video filter CGM Clone Grain (located in: Video Filters / CGM DVE Image Control) to the computer graphic or animation and open its settings.

Then drag the grainy video into the Grain Source well. You need only one second because the grain source video will be automatically looped.

The area where the grain will be added can be limited by setting Bezier points, adjust them to the size you need and render the result.

Done!

In the example the grain has only been added to the left half of the picture.

This is the rendered result of the effect. The screenshot at the very top of this workshop shows the result much better thanks to the CGM Magnifying Glass video filter.