The rest of screen is not that bright. Focusing on fresnel portion of screen more difficult than on plain groundglass screens. Not that great for astrophotography, but usable. 12mm reference circle and horizontal and vertical lines. Used when preparing slides for TV broadcasts.
Dotted lines indicate standard TV screen format.
Rangefinder blacks out at high focal ratios usually encountered in telescopes. Rest of screen not that bright. Focusing on fresnel portion of screen more difficult than on plain groundglass screens. Not that great for astrophotography, but usable. Utilizes the same matte field as Type B, but with lenses longer than 100mm the image in the viewfinder is easier to see.