Agfa Structurix D7

Structurix D7 is the reference film in Agfa's industrial radiography lineup. Every other Structurix grade is rated against it for exposure factor, which is why the BAM-certified spec sheet uses D7 as baseline. The name comes from the mean grain size of 700 nanometers, in the C5 class under EN ISO 11699-1. Speed sits at ISO 320 for radiographic work. Photographers who repurpose the sheets get a much slower film under visible light, somewhere in the ISO 50 to 80 range, because the emulsion is blue and green sensitive only.

Waygate Technologies, the Baker Hughes division that absorbed Agfa's NDT business, still makes D7 for inspecting welds, castings, and aerospace parts. It is a fine-grain film with high contrast, which translates into a punchy, short-scale orthochromatic stock when you point it at the sun instead of a steel pipe. Foliage reads grey, skies block, skin tones come out blocky.

The practical comparison is to Structurix D4 at the slow end and D8 at the fast end. D7 is where most photographic shooters land when they want speed without the coarser grain of D8. It costs a fraction of Adox CMS 20 II per sheet, which is why people put up with the orthochromatic response.

Develop in Rodinal 1:100 stand for compensating contrast, or in standard X-ray developer like G128 if you want what Agfa engineered. D-76 works in a pinch but the highlights compress hard. Handle under a red safelight. The base is clear polyester.

Formats are sheet only, in NDT sizes from 10 by 12 cm up to 35 by 43 cm, plus 70mm and 100mm roll for radiographic cassettes. Cut down to 4x5 in the darkroom.

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, where exposures past a minute are the norm, that correction stacks on an already long shutter time.