Agfapan APX 25

Agfapan APX 25 was the slowest panchromatic film Agfa coated for the consumer market, sold from 1989 until production stopped in 2002. The official story is that a precursor chemical for the emulsion went out of supply and the volume was too small to justify reformulating. The unofficial story is that nobody was buying ISO 25 film by then.

The character is the closest thing to a technical film that ever came out of Agfa's pictorial range. Resolution is high. Grain is essentially invisible at normal enlargement sizes. The curve is steeper than APX 100: APX 25 is contrasty by nature, and shooting it in flat overcast light gives negatives that print easily and read with snap. In direct noon sun, expect to fight the highlights or rate it down a third of a stop.

Rodinal is the developer. APX 25 in Rodinal 1:50 at the published time is the combination most photographers actually used, and the results are part of why the Agfa-Rodinal pairing has a near-religious following. Atomal FF was the in-house alternative and gave smoother midtones at the cost of acutance. FX-39 worked well for those who wanted finer grain without losing sharpness.

Compared with Ilford Pan F Plus at ISO 50, APX 25 was a hair finer grained and a stop slower, which often forced a tripod that Pan F let you skip. T-Max 100 was tabular and cleaner in the shadows but lacked the European tonal character that made APX 25 distinct. For large-format landscape, APX 25 sheets were a serious option that some Ansel-leaning shooters preferred to FP4+.

Sold in 35mm and 120 only. The earlier Agfapan 25 was available in sheet sizes before the 1989 APX reformulation, but APX 25 itself never made it into 4x5. Today only freezer stock survives and it is rare. Twenty-plus year old rolls go for collector prices, and base fog is part of the bargain.

Reciprocity exponent is 1.33. Zone Light Meter applies the correction past one second. A 10-second meter reading climbs to about 21 seconds at the negative; a 30-second reading runs closer to a minute and a half. For long-exposure landscape work, that math comes up when you are stopped down to f/22 in shade.