Agfa Isopan FF

Isopan FF was the slowest film in the postwar Agfa B&W catalog and one of the slowest panchromatic stocks any major manufacturer sold. Period data sheets list it at 13 DIN, which is ASA 16, with some later regional releases stretched to ASA 25. The slowness was not a defect. Agfa engineered Isopan FF for technical reproduction work where the resolution had to support wall-size enlargements and the photographer had a tripod and controlled lighting. ASA 16 with a generous tonal range was the trade.

Resolution figures from period testing put the film well past 200 line-pairs per millimeter on the right developer. Grain at full enlargement is barely visible, structurally tighter than even Adox CHS 25 II of the modern era. Compared with Kodak Panatomic-X of the same period, Isopan FF is slightly slower with finer grain and a longer shoulder. Compared with the original Agfa Copex Pan, Isopan FF gives less contrast and a smoother midtone curve, making it the better choice for full pictorial rendering rather than copy-quality reproduction.

Development is where most photographers got it wrong. The film needs a low-energy developer to hold the long scale. Agfa Rodinal at 1:100 with extended times brings out the resolution. ID-11 at 1:1 works for general use. Avoid anything aggressive: high-acutance developers blow the highlights and lose the latitude that justified using such a slow film.

Production ended in the late 1960s as Agfa shifted the slow-speed slot toward newer emulsions. Sealed boxes still circulate in 35mm and 120, occasionally in plate sizes for old technical cameras. Frozen rolls keep their resolution well. Warm-stored rolls develop a creeping base fog that defeats the purpose of the stock, and given the late-1960s production window every surviving roll is now well past that point unless it has been kept frozen.

Reciprocity exponent is 1.33. Zone Light Meter applies the correction past one second. A metered 30-second exposure becomes about 100 seconds at the negative. At ASA 16, tripod and long exposures are essentially the working assumption, so you will cross the one-second threshold on most frames. Plan for it and bracket conservatively.