Washi S

Washi S is repurposed motion-picture optical soundtrack film, rated at ISO 50, and it behaves nothing like a normal black and white negative. Lomig Perrotin started Film Washi in 2013 out of a Paris flat before moving the operation to ex-military containers in Brittany, where he hand-rolls short runs of stocks nobody else bothers with. S is one of the more shootable items in his catalog. It is also one of the strangest.

The emulsion is panchromatic but not fully red-sensitive, which is the kind of thing you only discover when you point it at a red shirt and it comes back near black. The anti-halation layer sits between the base and the emulsion rather than on the back, an unusual placement that helps explain the resolving power. Edge sharpness is striking even on a flatbed. Grain is essentially invisible at any reasonable print size.

Contrast is the catch. Out of the box the curve is steep enough that midtones almost disappear in direct sun, and the soot-and-whitewash negatives reviewers describe are not exaggeration. Shoot it overcast. Shoot it indoors under window light. Anywhere highlights are not screaming, the file has a tonal range that competes with anything at ISO 50.

Developer matters more than usual. Rodinal 1:100 stand for 45 minutes is the popular path because the dilution acts as a compensating developer. HC-110 dilution F at lower EI gets you closer to normal contrast. Avoid D-76 stock, which only steepens the curve. The closest peer in spirit is Kodak Technical Pan: same slow, high-acutance, contrast-prone behavior, different supply chain.

Available in 35mm and 120, plus 30.5m bulk for hand loaders. The cassette has an extended leader, so shoot three blanks at the start to clear it.

Reciprocity exponent is 1.31. Zone Light Meter applies the correction past one second, so a metered 30-second exposure works out to about 90 seconds at the negative. At ISO 50 you cross that threshold faster than expected, especially indoors at small apertures.