I have a Spencer Port-Land 8-inch lens, from Buffalo, NY; it is one of those variable soft-focus lenses with a doublet at some distance behind the iris diaphragm, and the degree of softness is controlled by the aperture used. In terms of optical configuration it is much like the well-known Rodenstock Imagon, but without the "sink strainer".
In practical use, I found it a very tricky lens to use; the spherical aberration, which accounts for its soft-focus effect, is very pronounced when at full aperture, so focussing is very painful, and any focussing discrepency can only be seen on the finished negative... not good!
The idea of the Imagon's "sink strainer" is to reduce the intensity of the secondary "halo" image, so as to make the sharp "core" image more pronounced. I have been entertaining thte idea of making a set of sink strainers for this lens, but of course I would need to get the specifications of the original Imagon ones.
According to my vernier caliper, the clear diameter of the aperture of the Spencer is 41.6mm, so if I can find images of the Imagon sink strainers I should be able to size them to suit.
Thank you!
In practical use, I found it a very tricky lens to use; the spherical aberration, which accounts for its soft-focus effect, is very pronounced when at full aperture, so focussing is very painful, and any focussing discrepency can only be seen on the finished negative... not good!
The idea of the Imagon's "sink strainer" is to reduce the intensity of the secondary "halo" image, so as to make the sharp "core" image more pronounced. I have been entertaining thte idea of making a set of sink strainers for this lens, but of course I would need to get the specifications of the original Imagon ones.
According to my vernier caliper, the clear diameter of the aperture of the Spencer is 41.6mm, so if I can find images of the Imagon sink strainers I should be able to size them to suit.
Thank you!