Kodak Tri-X 320 (TXP)

Kodak Tri-X 320 TXP is not the same emulsion as 400 Tri-X. Photographers who reach for it because they know 400 Tri-X from roll film are sometimes surprised. The TXP emulsion was designed around the tonal requirements of large-format work: a longer toe (meaning more detail in deep shadows before the curve bottoms out) and a longer shoulder (meaning gradual rolloff in the highlights rather than the abrupt clipping you get from roll-film emulsions optimized for miniaturized grain). The ISO 320 rating reflects that design; the film trades a third of a stop of speed for a wider contrast range.

Available in 4x5, 5x7, and 8x10 sheets. The 4x5 is the common format. Photographers doing zone-system work often prefer TXP to the finer-grained T-MAX 100 because the silver grain structure prints with more apparent depth on fiber paper. TXP in a 4x5 negative, developed in HC-110 at normal, and printed on a glossy fiber paper has a quality that people sometimes describe as a glass-plate look: sharp, slightly compressed in the midtones, with open shadows.

Development in D-76 1:1 is the standard starting point. HC-110 Dilution B pulls the highlights back slightly and is a better choice in contrasty light. Pyro developers (PMK, Pyrocat-HD) work well with TXP because the tanning action builds highlight density gradually, which suits the long shoulder.

The reciprocity exponent for TXP is 1.31. This is meaningfully worse than the Vision3 cinema stocks and noticeably worse than T-MAX films. Zone Light Meter applies the 1.31 exponent past one second. Long exposures are common in large-format work (contact printing setups, tabletop, interior architecture under available light), so the correction matters. A three-minute indicated exposure becomes closer to eight minutes corrected. Use a real reciprocity table or let the meter do the calculation.