Adox HR-50

HR-50 sits between CMS 20 II and a standard pictorial emulsion in terms of resolving power and usability. The film was originally developed for aerial surveillance use, where the combination of fine grain, high acutance, and a base thin enough to lie flat in a magazine without curl was operationally necessary. Adox makes it available to photographers as a technical curiosity with real pictorial applications.

The ISO 50 rating gives it a practical advantage over CMS 20 II: you can use it in normal outdoor shooting conditions without the stopped-down-to-f/22-at-noon limitation that an ISO 20 film imposes. The grain is finer than any standard ISO 50 emulsion and the edge sharpness is very high, which makes it productive for subjects where fine detail matters: architecture, landscape, technical copying.

Unlike CMS 20 II, HR-50 responds more normally to conventional developers. Rodinal at 1:50 or 1:100 gives sharp, slightly grainy results with the compensating action preventing highlight blowout. ID-11 or D-76 at 1:1 produces a cleaner result with slightly less acutance. The film does not require a specialized developer the way CMS 20 II does, though it benefits from careful agitation control to avoid streaking.

Available in 35mm, with 120 and 4x5 sheet rolled out at launch in 2018. The 120 supply has been intermittent because of backing-paper issues; sheet film has shipped in smaller runs through Fotoimpex.

Reciprocity exponent is 1.10, which is between the true linear response of CMS 20 II and the more pronounced 1.31 of conventional emulsions. Zone Light Meter applies the correction past one second: a metered 30-second exposure becomes about 50 seconds with the 1.10 exponent, a smaller correction than the standard but not negligible for multi-minute night exposures.