This example is very interesting because I have tried here to make a black and white focus on the colored picture.
Take a picture: First take colored picture to modify.
Draw a circle: Choose "e0e2ef" color and Ellipse tool (U key) to draw a circle shape.
Layer settings: Now click on the circle layer and make layer setting.
You will get it.
Now put this circle shape left bottom of the picture.
Image ready: Go to image ready, take some frame and move your circle shape left bottom to right bottom at every new frame in the animation window as I have done here.
Save file: Now go to File menu > Choose save optimized.
Recommend the tutorial