3D image stretching

Click on the pictures to see a more detailed view.

Rectilinear lenses keep straight lines in the real world straight on the image sensor. This creates an effect called 3D stretching or lean-over in which objects at the image edge seem to be stretched because they are being “flattened” onto a plane along the tangent angle from the lens. The wider the field of view (for rectilinear lenses), the more noticeable this effect. The benefit of this effect is increased resolution at the edges of the image.

In the picture above, both cars are the same width but since Car B is seen much more obliquely it appears to be stretched. The cars are the same width because they are in the same plane perpendicular to the camera and the lens images these equal planar measurements to equal distances on the sensor. The length is stretched due to flattening onto the sensor plane.

This compisited image was captured using a 5MPix camera. The same person can be seen at different distances from the camera as indicated by the red arcs on the ground. Notice that a person at 21ft from the camera at the center of the image is the same height as a person at 40ft at the edge of the image. The person at the image edge has more detail even though they are further away.