# Petzval portrait

> Two cemented pairs with a stop between them — the classic fast portrait lens.

**Joseph Petzval** · 1840, Vienna — for Voigtländer

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.

## Sources

- [Petzval lens](https://en.wikipedia.org/wiki/Petzval_lens)
- [Joseph Petzval](https://en.wikipedia.org/wiki/Joseph_Petzval)

## Links

- [HTML](https://www.loomrume.com/examples/petzval-portrait)
- [Open in Studio](https://www.loomrume.com/studio?template=petzval-portrait)
- [llms.txt](https://www.loomrume.com/llms.txt)