Kodak Technical Pan 25

Technical Pan was not designed for photography in the usual sense. Kodak built it for photomicrography, microfilming, and scientific imaging applications where resolving power mattered more than any other variable. The published resolution spec was 320 line pairs per millimeter under controlled conditions, which is roughly four times what conventional panchromatic films can do. That number got attention outside the lab.

The extended red sensitivity was a byproduct of the spectroscopic design. Technical Pan responds strongly to wavelengths out to about 750nm, well beyond the sensitivity cut-off of standard panchromatic emulsions. In practice this means foliage photographs slightly pale, skin tones shift warm, and atmospheric haze almost disappears in landscape work. Astrophotographers adopted it heavily through the 1980s and 90s because the red sensitivity captured H-alpha emission nebulae that appeared only as faint smudges on Tri-X or Plus-X.

The catch was development. Technical Pan compressed contrast brutally in standard developers. Kodak recommended TECHNIDOL, a phenidone-based low-contrast developer sold specifically for Tech Pan, to keep the curve linear enough to print. Shoot it with D-76 and you got blocked highlights and flat shadows. The film also responded extremely to development time, so a thirty-second error in the tank meant a measurably different result on the print. Serious users kept tight temperature control and a timer they trusted.

Kodak discontinued it in 2005. There was no direct replacement. Adox later introduced CMS 20, which occupies a similar ultra-slow high-resolution niche, but the extended red sensitivity and the specific contrast characteristics of Tech Pan are gone.

Reciprocity exponent is 1.33. A two-minute ambient reading stretches to about three and a half minutes of actual exposure. Zone Light Meter handles that correction past one second automatically, which matters for astrophotography work where base exposures are often several minutes to begin with.