KB-50 and R-50 are orthopanachromatically sensitized thin-layer black-white negative films. Efkes thin-layer photographic emulsion, fine-grain structure and coinciding contrast grade provide high edge sharpness and possibility for making large enlargements. Resolving power is 105 lines per milimetre. Sensitivity of Efke 50 is 17 DIN (40 ASA, ISO 40/17°, GOST 35), but by developing them in adequate developers films sensitivity utilization may be even twice incrased to 200 ISO.