Sound-on-film technology
Tigerstedt's greatest interest was in the field of sound recording. He had developed a prototype for recording sound on a metal wire as early as 1912 and was convinced that he could find a way to record sound directly on motion picture film. He started his first experiments in Helsinki using very primitive equipment. The sentence he attempted to record was in German: "Grau ist alle Theorie. Grün ist nur des Lebens Baum". Finally, he succeeded and he called his invention the "photomagnetophone". Unfortunately, his achievements did not gain any recognition, nor did he reap any financial gains from his invention, so he had to maintain a day job in order to earn a modest living and could only continue his experiments in the evenings and into the nights, sometimes working all through the night without any sleep.
After meeting his former schoolmate Alfred Nybom in Berlin, he succeeded in using Nybom's connections to gain access to a research laboratory and employment as an inventor. Film with audio was recognised as a commercially promising field of endeavour, but Tigerstedt's invention needed further development before it could be commercialised. There was as yet no technology available to electronically amplify the audio signal sufficiently to fill a large movie theatre. Tigerstedt also enlarged his vision of video transmission in the future. He wrote: "There will come a time when people can sit at home and follow events in the world through a device I now call the 'electronic eye'. When people get used to film with sound, they will soon adopt the electric eye, or electrophtalmoscope". When his father learned of his thinking, he tried to persuade him to not let his imagination carry him away, " ... otherwise you will surely end your days in the asylum in Lapinlahti."
Tigerstedt returned to Germany in 1913 and continued developing the photomagnetophone, but there was still no solution to the problem of amplification. He experimented with early versions of the vacuum tube and eventually was able to amplify the sound, but with disappointing results.
Tigerstedt also continued developing the electrophtalmoscope. The prototype consisted of vibrating mirrors in both the sending and receiving apparatus, using the photoelectric properties of a selenium element at the sender and a light source at the receiving end which was modulated using a Faraday device. The received picture was supposed to be displayed on a movie screen. Two electrophtalmoscopes were built and an experiment was conducted using an electrical cable running from London to Berlin. Tigerstedt arranged several demonstrations and gained a reputation as a knowledgeable scientist.
