Silberra U400

U400 is the fastest film in Silberra's Ultimate series and the one that announced the St. Petersburg chemists were doing something other than rebranding Aviphot. The Ultimate emulsion is a mixed-grain coating: flat tabular crystals layered with classic cubic grain, intended to combine the resolving power of a T-grain film with the softer tonal response of an older silver-rich stock. The result behaves differently from anything in the catalog of either parent technology.

The substrate is a thin polyester base inherited from the broader Ultima line, with an anti-curling layer that keeps negatives flat. The unexposed film carries a distinct greenish cast from the protective and anti-halation coatings, which can spook a first-time user. It clears in development. Silberra adds a 37th frame at the back of each cassette to counterweight first-frame fogging from loading.

Exposure latitude runs ISO 200 through 800 with the curve staying clean. James Harris at Emulsive shot a Nikon F2 roll at EI 1600 and got printable negatives with intact shadow detail, working without documented push times because Silberra has not published them. That gap is typical of the brand: serious emulsion, casual documentation.

Compared to HP5 Plus the grain is finer and tighter; compared to T-MAX 400 it carries more midtone softness and less of the technical edge that T-grain stocks bring to architectural subjects. Rodinal 1:50 for seven and a half minutes is the published time. D-76 1:1 at ten minutes is safer for predictable contrast. Xtol full strength at five and a half minutes runs cooler.

Available in 35mm in 36-exposure cassettes plus the extra frame. Silberra lists 120 rollfilm and a range of sheet film sizes for the Ultima line, though supply has been intermittent.

Reciprocity exponent is 1.31. Zone Light Meter applies the correction past one second. A 30-second meter reading becomes about 90 seconds at the negative, and a two-minute exposure stretches to roughly seven minutes. The mixed-grain emulsion has not been characterized in deep long-exposure tests, so bracket past one minute.