The (New) Stanford Light Field Archive

Geometric Calibration

For light fields acquired using our camera array, calibration was performed using the plane+parallax approach described in [8]. In this approach,

The cameras are arranged on plane.
The camera images are projected on to a reference plane parallel to the plane of cameras. This is done by a applying a homography which is represented by a 3x3 matrix. We refer to these as keystone corrected images.
The (X,Y) positions of the camera centers are recovered using parallax measurements. As described in our paper [8], these positions may be known only up to an unknown scale. However, this is not a problem for most applications. We have found this calibration sufficient for 3D recosntruction, synthetic aperture imaging, light field rendering and space-time view interpolation.

For each of the light fields, we provide:

A text file containing the camera positions. Each line of the file is of the following form:
Camera-id X Y
The camera id is an integer. (X,Y) are the coordinates of the center of projection of the camera, up to an unknown scale.
Homographies for projecting the camera images on to the reference plane (keystone correction). The 3x3 homography matrix for each camera is stored in a text file in row-major order.

For light fields acquired using the computer-controlled gantry, we provide the same information. The only difference is that the camera positions are obtained from the gantry instead of parallax measurements. The camera positions are in millimeters and our gantry is sub-millimeter accurate.

Our calibration error is less than 0.5 pixels. This error is primarily due to uncertainity in corner detection. A quantitative analysis of the error may be found in [2], Appendix A.

Color Calibration

Our procedure to compensate for the variations in color responses amongst the different cameras of our array is described in [3]. For light fields acquired using the gantry, no color calibration is needed as all images were taken with the same camera.