Til myke portretter er fortsatt mellomformat med Rodenstock Imagon uslåelig, med sine hullblendere langs periferien til å slippe inn valgfrie mengder oppmykingslys, det blir mykt uten å være uskarpt. Men det er sjelden jeg tar frem klenodiet!
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Beskrivelse: In 1979 Dr. Alfons Scholz, of the G. Rodenstock Optical Works Munich published the definitive scholarly exploration on the topic of Imagons with supporting photographs. The following is a précis of his thoughts and his history of soft focus lenses:
In a nutshell, the Imagon lens is based on a 2 element Achromat. One of the simplest lenses available. Imagons have 2 unique properties. a) Tremendous depth of field due to the fact that light is not resolved at the focal plane but exhibits instead a zone of focus and b) The ability to stay gently diffused even while sharpening up at small apertures.
Invented by Dr. Heinrich Kuhne (1868-1944) and still in production by Rodenstock, these lenses represent, in the purists sense, an ideological struggle that took place amongst lens designers prior to current times. Should a lens produce the sharpest technically correct image possible or should a lens produce an image the natural way that the human eye sees light, which is directly speaking, a low resolution interpretation of reality with fuzzy edges sharpened and refined by the brain.
The simplest photographs are pin hole images, image sharpness is affected by aperture, but the length of exposure is too great for general use. Daguerre and Niepce used the simple 1 element Wollaston (1812) Meniscus Lens in their cameras. In essence an eyeglass lens with a diaphram mounted at the front. This lens caused light to converge at the film plane thereby speeding the imaging process. The Meniscus lens was useful primarily in the near shooting range such as portrait work and was restricted to small film formats. In 1897 Henry S. Smith produced a 2 element 'semi achromat' in Boston which was used by Alfred Steiglitz for 5x7 and 8x10 formats. This lens produced a shimmering quality and was initially considered difficult to work with because different shooting circumstances produced wildly divergent results and also because shorter focal length lenses proved to be too soft.
In the 1920's in Rathenow Germany, Nicola Perscheid, a renowned portrait photographer approached Emil Busch A.-G. about custom making a portrait lens. Thus the Aplanat was born.* The design was inspired by the periscope which is two meniscus lenses, concave to concave, with the addition of a divergent lens cemented in between. Like the Meniscus and Smith lenses before it, softness was variable according to aperture such that by f 8 the image becomes sharp.
After the first world war Voigtlander introduced the Universal Heliar which was produced up until 1970. This design allowed softness at all aperture settings for large format work with longer focal lengths. In the 30's Ernst Leitz introduced the 9cm Thambar f2.2 for 35mm use. This 4 element design was replaced by the Hektor 125mm f2.5 after the 2nd world war. Both lenses produced soft images wide open, sharpening up as the diaphram is closed down.
It was in the 20's that Kuhn, who was a photographer, approached Dr. Franz Staeble, a lens designer in Munich, with his concept of what a lens should be, 'romantic softness without sugariness, blurring without a woolly effect'. The first Imagon hit the market in 1928 and was called Kuhn's Anachromat. In 1930 the Staeble lens works were acquired by Rodenstock and in 1931 the Imagon was introduced.
The Imagon was available in 3 focal lengths: 200mm H5.8, 250mm H5.8 and 300mm H7.7. *
The 200mm has a covering power of 154mm and therefore can be used on 4x5 without movement, although it is primary adapted to Medium Format cameras. The 250mm has a field of 180mm and is thus a better choice for 4x5. The 300mm covers 5x7 (220mm field).
Focusing an Imagon is technically challenging and should be done at the taking diaphram due to a focus shift which occurs when closing down. The discs can then be mounted to produce the halo effect for which the Imagon received it's patent. The subject is usually lit in a contrasty fashion to counter the softness of the lens, however at H 11.5 the Imagon produces a hard shape focus with very little diffusion. The Imagon is not simply a soft focus lens, but more accurately a lens with variable image production qualities that will reward the student of photography with unique interpretations of portrait and field work limited only by the imagination.