What you'll need
Starting in the Default workspace in Adobe After Effects, move the playhead to the beginning of the composition, select the video layer in the Timeline panel, and choose Animation > Track Motion. Make the Selection tool (V) active and then hover over the Track Point indicator in the (now visible) Layer panel until the cursor becomes a black four-way arrow. Zoom in to 200% to see this detail more clearly. Drag it to the spot you’re illuminating — somewhere with a defined edge or contrast. (Note the detailed pop-up as you drag.) Finally, click the Analyze Forward (play) button in the Tracker panel to generate tracking point keyframes.
Select the video layer and add a new solid to your composition (Layer > New > Solid). In the Solid Settings dialog box, set the dimensions to twice the size of your composition and make the color black (000000).
Click the Edit Target button in the Tracker panel and choose the black solid as the layer in the Motion Target dialog box. The layer name will then appear next to “Motion Target” in the Tracker panel. Click Apply and then click OK in the Motion Tracker Apply Options dialog box to accept the default X and Y dimensions being applied.
You’ll be switched back to the Composition panel, where the solid obscures the footage and shows the applied tracking data points. Move the playhead to the beginning of the composition and select the solid layer. Use the Ellipse tool to draw a mask that covers the portion of the scene you’re illuminating. In the Timeline, change the mask’s blend mode from Add to Subtract. Press F to reveal the Mask Feather value and increase it to between 200–250 to soften the mask edge.
Change the solid layer’s blend mode to Soft Light. You may need to click Toggle Switches/Modes at the bottom of the Timeline panel to display the layer blend mode options. Play the composition to see how the illuminated area stays on its target.
If the area of the clip outside the mask looks too dark, choose Layer > Solid Settings and click the color chip to change the solid’s color from black to a dark or light gray (try 3A3A3A). You could even pick a color tint to experiment with clip grading. As you click and drag the mouse around the color spectrum, the Composition panel will give you a live preview of the changes you’re making.
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