Testing RPX 25:
For a number of years now, I have gotten mixed results from this film. I want to love it. Slow films are wonderful and few in number. One can get a great tonal range, or at least in theory. I have always hoped to find a film which can replicate the long discontinued Panatomic X, and this hope I fervently projected in the direction of RPX 25.
With RPX 25, I originally expected as I think many have based on the name that the film would be similar to its antecedent, Agfa Pan 25. This is very much not the case. RPX turns out to be high in contrast in circumstances where one might not expect it. This I think is for two reasons. One, it is actually quite infrared sensitive. The difficult thing about infrared light is that one cannot effectively measure it with a standard light meter. These are not sensitive to infrared light (which is reasonable given that most films are not either, and meters would not work well with many films if they were). Under bright conditions with a lot of infrared light, one can easily overexpose RPX 25 by several stops, even with good metering. This leads to a negative with very high contrast. It looks almost like you shot it on lith film.
That was learning experience number one. OK, fine, let’s take the infrared light out of the picture – long exposures under low light conditions, N+1 processing. That gets you much better results, but this isn’t really practical under most shooting conditions, or with mixed subject matter, or with a roll of film shot under mixed lighting conditions, or with high contrast scenes, or with basically anything other than 4×5 sheet film where you can be very intentional about the development for each exposure, and you normally have two sheets of film and can calibrate better for the second of the two. In short, it isn’t practical.
What to do? Well, one thing I can tell you is, D-23 helps a lot. Use diluted 1:1, develop for 8 minutes. That helps to give a more reasonable average contrast with normal overall density. Rodinal is too contrasty. Even with N+1 development and a dilution of 1:100, it still very high in contrast.
But the second reason for getting mixed results with this film? Reason two why it seems to be too high in contrast and produce overly dense negatives? Way more simple. I think they just underrated it by one stop. Just shoot it at EI 50. I think this film is about a stop underrated for most uses. The first photograph in this post was shot on 120 roll film. I exposed two rolls on the same time under cloudy but bright lighting conditions. I made two initial exposures, one at what would translate to EI 25 for the metered light conditions and one that would translate to EI 50. I also made exposures using filters yellow 8, yellow 12, yellow 15, orange 22, red 29, heliopan IR 610, and ten stop neutral density for ten minutes.
My hypothesis was that the best would be those exposed at normal speed with a red filter or the IR610. Man, did I have high hopes for the IR 610. On other rolls, I had great results with that by the way. It’s in between red 25 and 29, close to the wratten filter that people used to refer to as ‘signal red’.
But the best results, hypothesis be damned, were the ones which were made with no filter at all just one stop under what should have been a standard exposure for the scene. Metering was done with a Gossen Starlight 2, which I use all the time and is very accurate, and I re-cheked in between every exposure so I’m sure it wasn’t my metering. So what I would tell you is, just give it one stop less than box speed under all but the most dubious lighting conditions where the isn’t any infrared light present in the scene or when using it for long exposures. It does work well for long exposures, but only if you have very good metering skills and the light is even and consistent.
Finally – Here it is as a 6×9. The original negative is a 6×12 negative. I think the framing holds up in either format. Too bad I can never find a 6×9 back for the Horseman SW612, huh? Seems like it would be nice.
