Large format film cameras use Fresnel lenses to overcome the problem of darkened corners when viewing the ground-glass image - the frosted glass on which the in

Large format film cameras use Fresnel lenses to overcome the problem of darkened corners when viewing the ground-glass image - the frosted glass on which the inverted image is focussed - redirecting the light rays that enter the lens around the edges and which would otherwise exit the back of the camera at the same angle, making the image appear increasingly dim towards the edges when the photographer looks directly at the back when focussing. The Fresnel re-orients these light rays so they are parallel to each other, pointing towards the photographer's eye [0] [0] Some example images here: https://www.onlandscape.co.uk/2017/08/large-format-camera-accessories/ https://www.onlandscape.co.uk/2017/08/large-format-camera-ac...