1067
sion, Ernest Lacan described it like “a true museum,”
with a gallery lit by transparent photographs on glass,
like stained glass (Moniteur de la photographie, No-
vember 16, 1876).
Even if he illustrated in other genres, Pierre Petit
remains particularly well-known as a portraitist. His
career, like those of Disdéri or Nadar, is a perfect il-
lustration of the popularity of the photographic portrait
and of the prosperity that of some large professional
workshops knew, as true “temples of photography.”
Helene Bocard
Further Reading
Michèle Auer, and Michel Auer, Encyclopédie internationale
des photographes de 1839 à nos jours, Hermance, Camera
Obscura, 1985; Pierre Petit photographer, Rochester, Inter-
national museum of photography at George Eastman House,
1980.
PETZVAL, JOSEF MAXIMILIAN
(1807–1891)
Josef Petzval is widely recognized as the father of photo-
graphic optics, being the fi rst person to apply mathemati-
cal computation to the design of a photographic lens.
Born in Spisská Belá—then in the Austro-Hungarian
Empire but today in Slovakia—he studied physics and
later mathematics in the Institutum Geometricum in
Budapest, now part of Budapest University.
After graduation, with a doctorate in physics, he
lectured part time at the Institutum, while also working
as an engineer in Prague. In 1838, he moved to Vienna
and took up the position of Professor of Mathematics
at the University of Vienna, where he spent the next
forty years. In the following year, he designed the rapid
portrait lens which bore his name and which revolution-
ized photography.
His interest in photographic lenses is believed to
have been triggered by a discussion with his friend and
colleague Andreas von Ettinghausen, after the latter had
returned from Paris where he had seen the daguerreo-
type demonstrated. Ettinghausen lamented the fact that
exposures with the new process were too long to make
portraiture a practical proposition, and Petzval embarked
on research to see if the design of lenses could be im-
proved to reduce exposures.
The result, computed before the end of 1839, and
produced in prototype by early 1840, was an innovative
design using two pairs of achromatic lenses that reduced
exposure times by more than 95%. Daguerre’s original
camera used a lens with an effective aperture of f/16,
while Petzval’s alternative offered a fi xed aperture of
f/3.6.
Descriptions of the portrait lens, in early manuals,
attest to its reliability and popularity. In the 1860s, Wil-
liam Lake Price described it as:
A front crown lens of unequal convex curves, to which are
cemented a double fl int lens of unequal concave curves;
the back combination is a crown lens of unequal convex
curves and a concavo–convex fl int lens at a little distance
from it. For more than a quarter of a century this lens,
without further changes in its construction than modifi ca-
tion of its curves, has been ised not only for the class of
pictures its name denotes but for a variety of others.
Petzval’s design used two pairs of color-corrected
lens glasses, their negative elements facing towards the
centre, on either side of a large central space. It was the
creation of the space between the pairs that achieved the
desired result. That result was a combination which of-
fered signifi cant correction of chromatic aberration and
coma, but like all such designs, suffered signifi cantly
from spherical aberration.
The design did not create a fl at image fi eld, and while
this was not a major issue when used to make small
daguerreotype portraits, it had severe limitations when
it came to larger plate sizes, as defi nition and sharpness
fell off signifi cantly towards the edges of the plate.
Given the small sizes of daguerreotype plates popularly
used at the time, and the fact that enlargement of the
photographic image was still decades in the future,
the loss of edge defi nition was not immediately seen
as a problem. A variation on the design later partially
eliminated the problem, and allowed the lens to be used
for architecture and landscape. It was, however, the
portrait lens which achieved greatest signifi cance in
the evolution of photography and, accompanied by the
considerably increased sensitivity of the daguerreotype
plate which resulted from the chemical innovations of
John Frederick Goddard, made portrait photography a
practical proposition. Between them, these two men and
their ingenuity effectively reduced exposure times from
many minutes to just a few seconds.
Being of limited means, Petzval could only afford to
patent his design within the Austro-Hungarian Empire,
and agreed, for a single payment, to license the manu-
facture to Peter Wilhelm von Voigtländer, who produced
the fi rst commercially available lenses in 1840. One of
the fi rst cameras to be sold with the Petzval lens attached
was Voigtländer’s unique metal-bodied daguerreotype
camera of 1841. About six hundred examples of this
camera are believed to have been manufactured, but
very few are known to have survived.
Petzval’s relationship with Voigtländer deteriorated
from 1845 when Petzval saw the success of the lens
and realized that, apart from his original payment, he
would not benefi t from it. When Voigtländer subse-
quently moved his manufacturing facility from Austria
to Germany, and outside the scope of Petzval’s patent,