Agfa Structurix D4

Structurix D4 is industrial X-ray film, not a pictorial photography stock. Agfa-Gevaert (now Waygate Technologies under Baker Hughes) still manufactures it for nondestructive testing of welds, castings, and aerospace parts. It shows up in still-photography registries because a small community of large-format and pinhole shooters buys the sheets and exposes them under visible light, where the emulsion behaves as a very slow, very high-contrast orthochromatic stock.

The Structurix line runs from D2 at the slow, ultra-fine end through D8 at the fast, coarse end. D4 sits on the slower side of the middle, listed in the C3 system class under EN ISO 11699-1. ISO 50 is the figure most photographers settle on under daylight, but the spectral sensitivity is blue and green only. Red barely registers. Landscapes look like Wratten 47 panchromatic prints from the 1930s: skies black, foliage grey, skin blocky.

The practical comparison is to Adox CMS 20 II or to early Kodachrome separation negatives. D4 holds detail a normal pictorial film cannot reach, but the tonal scale is short. Two stops of useful latitude is typical. Develop in dilute Rodinal 1:100 for stand development if you want compensating effects, or in standard X-ray developer for the contrast Agfa intended.

D4 is sold as sheets in NDT inventories at sizes from 10 by 12 cm up to 35 by 43 cm, and in roll form for radiographic cassettes. No 35mm. No 120. Large-format shooters cut the sheets down to 4x5 or 8x10 under a red safelight.

This is not a film to learn on. The latitude is unforgiving and the spectral response surprises new shooters. But for architectural copy work or the look of an emulsion that was never sold as art film, D4 is one of the few options left.

Reciprocity exponent is 1.31. Zone Light Meter applies the correction past one second. A metered 10-second exposure becomes about 20 seconds at the negative; a 30-second reading climbs to roughly 90. For pinhole work at f/256 or indoor sheets at f/45, that correction comes up on almost every frame.