I got some ORWO N75 Plus 400 film yesterday. There are some threads on this film out there. I will mention that it is an inexpensive 35mm negative movie film with rotary process and still photography characteristics unknown to myself.
The first test shown here is a test of film speed. This is a test relative to fresh Tri-X. Both films were exposed with a Wejex Daylight sensitometer and processed together about 30 minutes after exposure. Processed in Jobo CPP2 6 min at 24C in T-max developer one-shot. Films read with a calibrated Tobias TCX transmission densitometer.
The speed of each film was determined and Tri-X was defined as "400" to see where the ORWO falls relative to that. A 'minimum gradient' film speed test was done, rather than a '0.1 fixed value' test to avoid having to create a series of curves for each film.
The results are in the following graph.
The ORWO is a fast film but it is just slightly slower than Tri-X. In terms of error of this method, I'm using a standard deviation of 0.3 DIN units per the paper by Nelson on W-Speed.
So that gives Tri-X a range of 27.3 to 26.7 DIN and ORWO a range of 26.7 to 26.1, so they almost overlap.
I'll say they are very close. Based on this I'll meter them the same.
This was not a development test pre say, but I can see that the ORWO does not respond as well as Tri-X to Tmax developer. I'll probably use a time that is 25% greater than my time for Tri-X.
SPECS: ORWO emulsion number N62-1, Roll 1711 25d, Box speed 400 daylight, 250 Tung.