Adox KB 21

KB 21 was produced by the original Adox Fotowerke in Frankfurt from roughly 1952 to 1973. It was the ISO 100 member of a three-stock B&W line that also included KB 14 at ISO 25 and KB 17 at ISO 50. When DuPont bought Adox in 1962 and eventually wound down the German B&W line, the machinery and recipes went to Fotokemika in Samobor, Yugoslavia in 1972, where production continued under the Efke brand. The Efke KB 100 you could buy until 2012 was essentially the same film.

The emulsion is a single-layer ortho-panchromatic silver-rich coating with cubic grain, which is the whole story of why these films look the way they do. Modern Ilford Delta 100 and Kodak T-Max 100 use tabular crystals that resolve more cleanly. The cubic structure on KB 21 gives a different micro-contrast, a different rendering of skin texture, and a tonal curve that holds shadow detail in a way modern stocks do not quite replicate. Leica shooters in the 1950s used it heavily.

Spectral sensitivity is ortho-panchromatic, with softer red response than fully panchromatic films like Plus-X or HP3. Red lipstick and red brick render darker than the eye sees them. For street and documentary work that gives a slightly more sculptural rendering of faces.

If you have rolls in the freezer, expect base fog. Anything sealed and stored cold since the 1970s might be usable. Anything stored at room temperature is probably a base-plus-fog disaster. Test a roll at box speed and at 50 before committing a session.

Formats originally included 35mm cassettes, 120 spools, and sheets through 8x10. Nothing has been manufactured under the KB 21 name since 1973. Current Adox CHS 100 II in Germany is the closest continuation, though reformulated rather than identical.

Reciprocity exponent is 1.31. Zone Light Meter applies the correction past one second. A 30-second meter reading becomes around 90 seconds at the negative. For freezer-stock testing where you might be exposing into ten or fifteen seconds to check base fog, that correction stacks fast.