In 1840 Johan Christoph Voigtländer’s optical company, Voigtländer, introduced the Petzval Portrait Lens. Founded in 1756, Voigtländer’s company is the oldest name in cameras. The Petzval Lens was developed based on analytical calculations and designed and calculated by mathematician Professor Jozef Maximillian Petzval in Vienna with further development assistance from Voigtländer’s grandson, Peter Wilhelm Friedrich von Voigtländer. The Petzval lens was the fastest lens at this time with an aperture of f/3.7 as a result of exposure times being dramatically reduced to one minute with this new 149mm lens.
]In 1841 Voigtländer produced the Daguerreotyp-Apparat Camera – the first camera made from metal. The Petzval Lens was mounted inside of the Daguerreotyp-Apparat camera which consisted of a tube that housed the lens. The tube was then mounted on a conical body with another conical section fitted over the focusing screen and a magnifying eyepiece attached for focusing. After focusing, a lens cap was put on, the camera removed from the stand and transferred to a dark room where the viewing cone and focus screen were replaced with a Daguerreotype plate and then returned to the stand. Once it was returned to the original position, exposure was then made by removing the lens cap. Afterwards the camera was returned to the dark room and the plate was removed and processed.
To learn more about the Petzval Lens, check out this article written in-depth on it: http://antiquecameras.net/petzvallens.html
Assistant Executive Director Department Chair Investigation & Research Education Resource Photography & NPS Photography Team
at NPS of Texas
Sheri has always had an interest in the paranormal – from watching different paranormal shows over the years to having déjà-vu experiences throughout all her life that she has tried to put an explanation to. When her dad passed away in March 2010she began her journey into the paranormal. She has had several encounters over the years since starting in the field & takes more of an “old school” approach to her research in the paranormal. She is a supporter of today’s modern technology being used on investigations & encourages the use of various tools on investigations. She is always looking for a new ‘old school’ method to try on investigations & employs the use of trigger objects in an effort to get a response. She became fascinated with the pendulum after using a set of original jailer’s keys as a trigger object on an investigation at a local historic jail & they began to sway in response to questions.She is a huge proponent of education in the paranormal field choosing to debunk things immediately by trying to recreate situations & experiment to find logical answers to things that have happened or been captured in photographs or on video in an effort to prove or disprove paranormal activity. She & her team focus on private residential cases as well as educating the public on paranormal investigation & research. You will often find them assisting & consulting with other teams on theircases. Sheri is a certified paralegal and Notary Public for the State of Texas. Her professional background includes working in the legal field, sports marketing, event coordination & business management. She serves as Assistant Executive Director of NPS and the Department Chair overseeing Photography and the NPS Photography Team. Sheri leads the Investigation & Research Education Resources for NPS which provides information, links, & articles surrounding education in the paranormal field. She also writes articles periodically for the NPS’ website that are tied to photography & education. She is one of the founders of NPS of Texas, a paranormal research & investigative team based out of Dallas, Texas.
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