Waist Level Optical Viewfinder for Cameras (25mm diameter lens)

This is the case for a waist level optical viewfinder I designed. It fits into standard hotshoe/coldshoes.

Including a square mask as an example, but you can change the mask to change the aspect ratio of the frame.

You will need a 25mm diameter convex lens for the front, a small 25mmx25mm square mirror for the inside, and a 30x30mm fresnel lens with a 28mm focal length for this design.