Ilford HP4

Ilford introduced HP4 in 1965 as the successor to HP3 and ran it for eleven years before HP5 took over at Photokina 1976. The two HPs overlapped briefly: HP3 stayed on shelves until 1969 while HP4 ramped up. It launched in 120 and 127 first, with 400 ASA 35mm cassettes arriving the following year. The film was Ilford's working-press emulsion through most of the late sixties, the years when Fleet Street still ran on roll film and the Magnum agency was filing prints out of Saigon.

The published box speed was 400 ASA in ID-11, climbing to 650 in Microphen. That dual rating was a real selling point at the time. Tri-X in the same period was rated 400 in D-76, faster in HC-110. HP4 gave press shooters a comparable speed advantage without leaving Ilford's chemistry. The grain was conventional cubic silver, larger and more pronounced than HP5+ would later achieve, with a curve that sat between Tri-X's punch and FP3's restraint.

HP4 has been out of production since 1976. Any roll you find now is at least fifty years old, and the typical complaint when shooters develop found stock is heavy base fog from cosmic radiation and damp storage. Rodinal handles fogged stock better than most: the high dilution gives a compensating effect that pulls some image back out from under the fog level. ID-11 still works on freshly shot rolls that have been frozen since the seventies. Microphen too. Skip Microdol-X.

There is no current production in any format. The film exists today only as freezer stock, estate cans, and the occasional bulk roll on eBay. Treat any roll as a gamble.

Reciprocity exponent is 1.31, which is the conventional silver-grain baseline for this era and matches Tri-X almost exactly. Zone Light Meter applies the correction past one second. A 30-second meter reading climbs to roughly 90 seconds at the negative. With aged stock you should bracket past that anyway; the base fog and the half-century of storage will eat exposure in ways no curve compensates for.