Yokoyama Seisakusho (横山製作所) was a Japanese company based in Shiba, Tokyo (today Minato),[1] c.1939, and about which little is known. The company offered a flash synchronization device for large format roller-blind shutters, featured in the January 1939 issue of Asahi Camera. The customer had to turn in his/her own shutter for the modification, which cost ¥5. The special 15-inch synchro cord was sold for ¥1.9, and further 15-foot extension cords were available for ¥1.60.


  1. The address in 1939 was Tōkyō Shiba-ku Shinmonzen 13 (東京芝区新門前一三). Source: column in Asahi Camera January 1939, pp.190–1.


  • Asahi Camera. "Atarashii kikai to zairyō" (新しい機械と材料, New equipment and materials), January 1939, pp.189–91.