Eastman · ISO 80 B&W negative
Eastman Plus-X 5231
Plus-X 5231 is the motion picture twin of the still-photography Plus-X that Kodak discontinued in 2010. Eastman introduced the 5231/7231 80D/64T variant in 1956 as a panchromatic cine negative rated EI 80 daylight and EI 64 tungsten. The still-film Plus-X went away. The cine stock 5231 was discontinued by Kodak in 2010 alongside the still-film Plus-X, and what circulates today is residual inventory repackaged by specialty dealers like Ultrafine and Film Photography Project.
The film has a remjet anti-halation backing, the same complication that defines all motion picture negative stocks meant for projection prints. You cannot run it through a standard B&W developer without first removing the remjet, or the carbon-black layer will contaminate the chemistry and leave streaks. Most still shooters buy it pre-stripped, or do the wash-and-wipe pre-soak ritual manually.
Rated at box ISO 80 daylight and 64 tungsten in motion picture terms, still photographers commonly rate it at 125, treating it as identical to the discontinued Plus-X still emulsion. Rodinal does not pair well; the high-acutance behavior coarsens the grain in ways the film's gentler character does not support. XTOL 1:1 or D-76 stock give cleaner results.
Compared with Tri-X 400 the contrast is higher and the shadow drop is faster, but the grain is finer at the lower ISO. Compared with Eastman Double-X 5222 the look is similar in cinematic structure but lower contrast and finer grain. For diffuse outdoor work, Plus-X was the choice and 5231 still is when you can find it.
Format availability is awkward. With Kodak production ended in 2010, the film survives only through third parties bulk-loading 35mm cassettes from leftover motion-picture cores. There is no 120 and no sheet option.
Reciprocity exponent is 1.31. Zone Light Meter applies the correction past one second. A 10-second meter reading becomes about 22 seconds at the negative, and a one-minute exposure stretches to roughly two minutes forty. For interior work, the correction kicks in fast at the slower ISO.
How the app handles this stock
- Box speed: ISO 80. Picker exposes pull/push chips so you can shoot it at any speed you want and the meter follows.
- Reciprocity: Above one second the app raises metered time to the power of 1.31.
- Expired film: if you load an old roll, set the expiry year and storage in the app and the ISO scales for you. B&W negative decay rates are baked in.