This camera is 25mm for 4x5 inch format (about 8mm in regular photo aperture). By adding additional frames and deepening the camera, you can add 25mm for each frame. I have the camera and two additional frames; thereby having 25mm, 50mm and 75mm focal lengths. One advantage of a pinhole camera is that everything is in focus, near or far.
These photos are four of the first eight exposures taken and developed. I was nicely surprised at the outcome, and I consider these to be a result of "educated serendipity". All four were taken at 25mm, very wide angle and very close. Working with a pinhole camera is going to be fun!