Originally Posted by
Bob Salomon
No, the 250mm is the focal length for 45 if you want the desired halation the Imagon is known for at the proper apertures for portraiture with the Imagon.
The Imagon is not designed to be used with the aperture ring in the shutter. It is made to be used with the three disks that set the T stops on the lens and none of them will reach f22. The most commonly used disks for the Imagon used for portraits will be the largest opening disk or the middle one. These will result in T stops from 5.8 to 9.6. Also frequently used for maximum halation is no disk which is also 5.8.
For the best Imagon effect you need direct light (not umbrellas) and a lighting ration of about 5:1.
The Imagon design throws a peripheral image from the outside of the lens over the image created from the center of the lens. The amount of the halation is controlled by how much of the center of the lens is used (controlled by the size of the center hole of the disks) and how much of the peripheral image is used (controlled by how open or closed the holes surrounding the center hole are). The Imagon is quite sharp when used with the disk with the smallest center hole with all of its outer holes closed.
So no, it will not be satisfactory, if you want the effects the Imagon is known for, on 4x5.
If you want a copy of the Imagon instructions in hard copy mailed to you, if you are in the USA, let me know and I can copy the booklet that came with the lens.
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