Historical-Photography Tools & Calculators
Free, practical tools for exposure, dating, and archiving — correct a long exposure, convert ISO to EV, size a scan for print, scale a historical ratio, and identify a process from the object in your hand.
Reciprocity & Exposure Calculator
Correct a metered exposure time for reciprocity failure — the long-exposure effect that made historical emulsions progressively less sensitive the longer the shutter stayed open
ISO↔EV Converter
Shift an exposure value between ISO ratings — translate a modern meter reading into the terms a slow, historical-speed emulsion actually needs
Print DPI & Size Calculator
Work out the print size a scanned plate supports at a given resolution, or the scan resolution needed to hit a target print size, in inches and centimetres
Dilution Ratio Calculator
Scale a concentrate-to-water ratio from your own reference source to a target batch or available-concentrate volume — plain ratio arithmetic, not a chemical formulation
Collodion Ratio Calculator
Scale a multi-part historical recipe ratio — from your own archival or reference source — proportionally to any target batch size
Photo Process Identifier
Answer a few questions about support material, surface, mount, and case to get a likely process match — daguerreotype, ambrotype, tintype, cabinet card, or carte de visite