The ground glass

In order to focus the camera you need a ground glass. It should be made of plastic so that it will not break on rough handling. I have mounted a ground glass between frames of cardboard to place it at the film plane when it is pushed into place.

It is well advised to mark the centre of the image with a cross (not visible in the image to the right) as it is not always easy to see where the center is when using the camera. Parts of the image may have very different lighting, and the edges tend to be quite dark.