A History of the Imagon lens by Dr. Alfons Schultz
There seems to be some controversy about the Rodenstock Imagon 200mm lens, specifically which format is it best suited for ?
According to the instruction manual from June 1978 "The 200 mm lens is usable up to 9x12 cm or 3 ¼ x 4 ¾ inches and the 300 mm lens up to 13 x 18 cm or 5x7 inches." 

Before WWII Rodenstock introduced 120 mm (6x6) and 170 mm (6x9) Imagons. Apparently they were not big sellers and the last 120 mm Imagons were cleared out in the 1960's. The 360mm Imagon (8x10) was discontinued before WWII.

In North America it is a common practise for photographers to photograph using 200mm Imagons on both medium format cameras and on 4x5 sheet film cameras. The main issue is not just coverage but usability.

Dr. Alfons Scholz of Rodenstock was a great Imagon scholar. In his book he explains his preference:

"The most favorable combination of camera and lens available is the Imagon 200 mm with the size 9 x 12cm. Full use of the field angle, unlimited aperture sequence, advantageous spatial depth, all these things are only possible with this combination. Anyone who does not want to use the Imagon for only one purpose, but who wants to make the most of his lens, will have to select the 200 mm lens and use it with a 9 x 12 camera."

The G. Rodenstock Optical Works Munich has been manufacturing the Imagon since 1931.
 

Rodenstock Imagon 200mm f5.8
  Rodenstock Imagon 200mm f5.8 BOXED w 3 Discs, Inst, Rear Cap, Hood, ND4
 

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.

H 4.5/120 mm (6x6 cm c.1940-60), 150mm, 170mm and 360mm Imagons were also available.
 


The Imagon lens or miniscus is a 2 element Achromat mounted at the rear of the shutter. Because there is no glass at the front of the shutter only a rear lens cap was supplied. The coating is magnesium fluoride.


The Rodenstock Imagon 200mm was factory mounted in a Copal #3 shutter. Early versions were supplied in a hard custom case with 3 H Diaphram Discs, Lens Hood, ND4 Filter and rear lens cap.

In this example a Hasselblad Bellows is used to focus the Imagon to Infinity, for portraiture or for close up work.


Hasselblad adapters were independently machined for this purpose.


Variations in the medium format mounting of the Imagon 200mm abound. Rodenstock offered a Zork-Tubus / Imagon solution for the Mamiya RB67 180mm lens. You unscrew the front element nascel of the 180mm lens screw in the threaded Imagon assembly as shown below.
Mamiya RB67 180mm Zork-Tubus / Imagon

Mamiya-Sekor SFC 150mm f/4  uses 3 Soft Focus Discs to increase sharpness.
Fits all versions of the RB67 RZ67.
Mamiya-Sekor SFC 150mm f/4  Soft Focus


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