Bi-Lateral Symmetry
Photo Activity from
Oswego City School District
This enjoyable activity comes from the Oswego City School District and was posted on
Jill Britton's excellent website. This activity may be used in geometry or calculus when
studying the concept of y-axis symmetry.
In most cases, the left side of a human face is close to being the mirror image of the right side.
The first photo is the original photograph of my grandson James. The second and third photographs
are composite pictures made by merging each side of the first picture with its corresponding reflection.
If the line of symmetry is drawn through the center of each of the composite pictures, each point of
the picture on one side of the line has an image point in the other side.
The composite pictures are symmetric with respect to this vertical line.
Using a digital camera, take photographs of the students in your class.
Try to get the students to look directly at the camera.
Using a photo-editing program or a drawing program, such as Adobe Photoshop or
Paint Shop Pro, create composite drawings such as those shown above.
For Adobe Photoshop Elements:
(1) Load the image and save it under a different name.
(2) Use the RECTANGULAR MARQUEE TOOL to select the left half of the face.
(3) Then Select EDIT / COPY.
(4) Then select EDIT / PASTE.
(5) Then use the MOVE TOOL to position the left half of the face over the right half.
(6) Then select IMAGE / ROTATE / FLIP LAYER HORIZONTAL to flip the right half.
(7) Use the BLUR TOOL to soften the vertical line in the middle.
(8) Same under a different name.
(9) Repeat the process for the right side of the face.
For Paint Shop Pro:
(1) use your selection tool to outline one side of the photo,
(2) under Image, choose Mirror,
(3) drag the new image so it will create a new face,
(4) crop your new image, and
(5) save the photo.
(6) Repeat the process for the other side of the face.
