Daguerreotypes needed light. Petzval, a mathematician, calculated a fast portrait lens for Voigtländer: two cemented doublets and a stop. It opened around f/3.6 when most camera lenses were still f/15. Sitters could hold still for seconds instead of minutes.
He never saw much money. Voigtländer did. The look is sharp in the middle and swirls at the edge — still copied as “Petzval bokeh”. This bench is the layout, not the brass barrel: two doublets, stop between, white on a meter.