Ansco and Bausch & Lomb
9 and 14 researched events on one shared scale. Ansco 1840–1967, Bausch & Lomb 1853–present.
The axis stretches where either maker has research and collapses where neither does, so a year sits opposite the same year on both. Event counts differ because research depth differs, not because one company did less.
Ansco1840–1967 · 9 events · 2 concurrent threads
Bausch & Lomb1853–present · 14 events · 2 concurrent threads
2 spans collapsed, 15 years in total, where neither maker has a research point: 2000–2006, 2014–2021. Collapsing keeps a short-lived maker readable beside a long-lived one; the years are removed from the drawing, never from the record.
Read either maker on its own: Ansco · Bausch & Lomb