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AnalogFixerDarkroom chemistry for black-and-white film
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Sensitometry

Characteristic curves, density measurement and the published data sitting behind box speed, development time and contrast index.

In this section

  • Contrast Index, BETA, and average contrast name different targets

    Sets Kodak F-4017’s numeric Contrast Index 0.56 starting-point claim, J-86’s 0.60-for-T-MAX-400 / 0.56-for-other-films split under T-MAX Developers, J-109’s CI-column matrix (0.56 on Kodak box-speed rows; 0.58 on Ilford box-speed rows under XTOL), F-4016/F-4043’s non-numeric diffusion-enlarger contrast wording, ADOX CHS 100 II’s BETA 0.65 medium-contrast column, and Ilford FP4 Plus / HP5 Plus qualitative “average contrast” language side by side as incompatible published contrast-target kind of claimes.

  • Manufacturer reciprocity corrections use four incompatible formats

    Sets Ilford’s December 2023 continuous Tc = Tm^p sheet, ADOX CHS 100 II’s October 2020 discrete multiplier lookup, Kodak T-MAX 100 F-4016’s June 2018 aperture-or-time table, and Kodak TRI-X F-4017’s December 2016 aperture-or-time-and-development table side by side as a dated correction-format matrix, recomputes only source-supported examples, and shows why those published outputs cannot be collapsed into one universal reciprocity number or used to rank emulsions.

  • ISO and EI name different claims on published film sheets

    Sets Ilford FP4 Plus and HP5 Plus (November 2018) ISO-versus-EI splits — including Ilford’s note that recommended EI ranges are practical evaluations and not foot speed as in the ISO standard — beside Kodak T-MAX sheets that call the nominal speed an Exposure Index determined in a manner published in ISO standards, F-4043’s instruction to use those EI numbers on meters marked ISO/ASA or ISO/DIN, and ADOX CHS 100 II’s ISO-only speed line, showing that the same dial numbers are not one published kind of claim across these sheets.

  • Ilford’s reciprocity floor is half a second or one second

    Sets the November 2018 FP4 Plus and HP5 Plus fact-sheet floors — no compensation between ½ and 1/10 000 second; compensate when longer than ½ second — beside the December 2023 Film Reciprocity Failure Compensation sheet’s “one second or less” floor, shows that those sheets share the FP4+ 1.26 and HP5+ 1.31 exponents while disagreeing on the floor and on whether the fact sheets used one factor for all films, and works the power-formula arithmetic that cannot increase exposure for metered times below one second.