The stability of a spectral sensitization varies. In general terms the more into the infrared, the lesser the stabilty.
So there is a great chance that your film has lost that IR, if not red at all, sensitization, if it is a film made by ORWO.
Though your film may also be of recent make from Filmotec branded as ORWO, then in the best case one should apply a filter factor of 8.
-) use different filters from dark red, to very near IR filtration
-) make a series of exposures starting at the low end of the film-speed range.
-) aperture and shutter speed alone do not matter at all if it is about achieving an IR-effect. It is only the combination, the exposure value (amount of light hitting the film) that matters.
Last edited by AgX; 11-12-2013 at 04:03 AM. Click to view previous post history.