The nadir camera Level 1 images have a swath width of about 376 km, compared to 414 km for the off-nadir cameras. The widths are different because the focal lengths of the MISR cameras change in relationship to the varying distance to the Earth for the different cameras. When viewing the same Earth area with a more oblique-pointing camera the focal length must be greater in order to preserve resolution. All of the camera images are 1504 pixels wide, and the focal lengths of the D, C, B, and off-nadir A cameras are chosen so that each pixel is 275 m wide. However, the nadir A camera uses the same focal length as the off-nadir A cameras, so each of its 1504 pixels is only 250 m wide. Another factor affecting overlap is Earth rotation during the time interval between when each camera acquires its image of a given area. The area of overlap among the cameras depends on latitude. Even though the forward and backward D camera (for example) have the same swath width, it is possible for the common area viewed by both to be less than 414 km.