Ilford · ISO 50 B&W negative
Ilford Pan F (original)
Original Pan F is the slow Ilford emulsion that ran from 1948 until the Pan F Plus reformulation in 1992. Some Ilford histories trace the Pan F line further back to the 1930s Selo era, but the post-war 1948 introduction is the version most photographers mean by original Pan F. At ISO 50 it was, and remains in its current Plus form, one of the slowest panchromatic 35mm negatives in serial production. Ilford has been openly cautious about touching the emulsion. The published position is that customers are attached to the specific curve shape, so revisions get held back. The 1992 Plus update reportedly improved grain and push tolerance, which tells you what the original was weak at.
The character that earned Pan F its following: extreme fine grain, high acutance, a contrasty curve, and a long shoulder that resists blowing highlights even when the scene is high key. Architectural shooters and landscape workers loaded it for the resolution. The cost was speed. ISO 50 outdoors at f/8 lands you at 1/125 second on a sunny day, but indoors or in shade you need a tripod.
The other weakness was latent image stability. Ilford recommended developing exposed Pan F within three months of exposure, a tighter window than HP5 or FP4 needed. For travelers who came back from a trip with a half-shot roll, the late frames could come out dense and muddy.
Developer of choice was usually Microphen for tighter grain, or Perceptol for the lowest possible granularity at the cost of half a stop of speed. ID-11 at 1:1 was the standard reference. Compared with Kodak Panatomic-X, also long gone, Pan F gave slightly more contrast and similar resolution.
Original Pan F is long out of production. Freezer-stock rolls turn up on the used market, but anything not stored cold for the last three decades will show base fog and reduced contrast.
Reciprocity exponent is 1.33. Zone Light Meter applies the correction past one second. A metered 30-second exposure climbs to roughly 100 seconds at the negative. At ISO 50 on a tripod, you will cross that threshold often.
How the app handles this stock
- Box speed: ISO 50. Picker exposes pull/push chips so you can shoot it at any speed you want and the meter follows.
- Reciprocity: Above one second the app raises metered time to the power of 1.33.
- Expired film: if you load an old roll, set the expiry year and storage in the app and the ISO scales for you. B&W negative decay rates are baked in.