Kodak Aerographic 2403

Tri-X Aerographic 2403 is the high-speed cousin of Plus-X 2402, built for low-altitude mapping and low-light aerial work where 2402 ran out of shutter. Aerial speed is ISO-A 320. The same warning hits every aerial film: that number assumes development to roughly gamma 1.80, far steeper than pictorial work wants. Pull contrast back and the effective speed drops. Ground photographers settle around EI 80 to 125 with D-76 1:1 at standard times.

The emulsion has extended red sensitivity for haze penetration, the same family trait as 2402. It runs more contrasty than retail Tri-X 400 even at reduced development, on a thin 3.9-mil ESTAR base with a dyed-gel anti-halation backing. Grain is moderate. Resolution is high enough that 4x5 cuts from bulk hold up at 16x20 prints. Kodak later replaced 2403 with SO-050 Tri-X Aerocon, essentially identical properties on a different base thickness.

ESTAR is the practical darkroom detail. It does not curl like acetate, does not snap on a reel, and is hard to tear by accident.

Community use mirrors 2402: large-format shooters cutting 9.5-inch or 70mm bulk down to sheet sizes for a fraction of fresh sheet-film cost. The look has a harder edge than retail Tri-X 400 due to higher native contrast, landing somewhere between FP4+ and a normally-developed Tri-X 400 if you pull development by about twenty percent at the conventional dilution. For documentary or environmental portrait work on 4x5, that contrast reads as authentic.

Discontinued, replaced first by SO-050 and quietly removed from the catalog. Surplus only, thirty to forty years old.

Formats were 70mm, 5-inch, and 9.5-inch wide rolls. No retail 35mm, no 120, no pre-cut sheets. Self-loading and self-cutting is the cost of entry.

Reciprocity exponent is 1.31. Zone Light Meter applies the correction past one second. A metered 30-second exposure becomes about 90 seconds at the negative. At ISO-A 320 in daylight the threshold rarely matters; at lower pictorial EI in interior work it comes up routinely.