To Cut the Composition’s Work Area Lengh

• 1. In the timeline, you'll see a work area bar — it's the blue bar that spans across the timeline.

  2. To adjust the work area, drag the start (left) or end (right) of the bar to define the section you want to keep.

  3. To trim the composition to the work area:

     • Right-click on the work area bar and select Trim Comp to Work Area.

     • This will remove everything outside the work area and trim the composition’s time range.

 Cut a Round Part of Image in AE (Create a Circular Mask)

• Select the image layer.

• Press Q to activate the Ellipse Tool (if Rectangle shows, click and hold to choose Ellipse).

• Double-click the Ellipse Tool to apply a perfect circular mask to the center.

• Or manually click-drag a circle over the area you want to keep.

• In the Timeline, under the layer, expand "Mask 1" and change the Mask Mode to:

  • ✅ Add – shows only the circular area.

Use Mask Expansion to grow/shrink the masked area.

How to hide the particualr area (Use a Mask to Hide the Area)

• Select the image layer in the timeline.

• Choose the Pen Tool (G) or Shape Tool (Q).

• Draw a mask around the part you want to remove.

• In the Timeline, set the Mask Mode to Subtract.