Hey, listen — for the record, this is ORWO TF-8. They used it in the past to picture sound.
Got a canister of it and started looking for any technical info. That’s where I hit the internet wall of “9 results found”. As I learnt in a similar case — for such old materials you shall search the old way. ORWO Kine- und Fernsehfilme book has a datasheet for TF-6.
My Russian 300-something pages “A handbook of photo materials” gave me further details: when new TF-8 had a GOST sensitivity between 16 and 32, that corresponds to ISO 20 – 40. Contrast to be expected if developed with ORWO 20 for 4 – 5 min. shall be around 3.6. May be hard enough for recording Klaus Meine’s Rock you like a hurricane, but I intend to soften this thing.
Loaded a piece of it in an old ORWO cassette and had a test strip shot, starting from F/8 1/60 all the way down to 1”. Then souped the film in A-49 for 10 min. @ 20° C. Here is a part of the test strip.
The verdict for my emulsion is ISO 12. So it shall live an adventurous life. Took 2 rolls of it on my next trip to the mountains and here are the results.