Kodak and Rodenstock
12 and 8 researched events on one shared scale. Kodak 1880–present, Rodenstock 1877–2013.
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.
Kodak1880–present · 12 events · 3 concurrent threads
Rodenstock1877–2013 · 8 events · 2 concurrent threads
Read either maker on its own: Kodak · Rodenstock