I am fascinated by this event. I brought out my empty 35 mm camera and found
to my amazement that this half lens thing works if the obstructing object is
out side the filter I have covering the lens. If the obstruction is at the
lens surface, then there is a dimming of the image with some obstruction. The
lens is obviously more complex than I knew. What fun!
I had only done this before with a simple lens to emphasize that any of the
light rays from an object will help form the image. Now I will need to do
some good drawings of what I think is in the lens. Thanks!