View Full Version : About Fujinon SF (Soft Focus) lenses

david clark
30-Aug-2001, 01:29
Hi, does anyone know if the Fuji soft focus lens is the same kind of animal as t he Imagon? Thanks, David

Bob Salomon
30-Aug-2001, 14:38
No it is a different technology. The Imagon is 2 elements, both in front of the shutter with the disk in front of the lens.

Fuji is 3 elements, one behind the shutter and does not have the front mounted disk.

the Imagon uses F stops from 5.6 to 22 by adjusting the aperture of the shutter.

The Imagon uses H stops from 5.8 to 11.5 controlled by the disk used and the amount of opening of the surrounding holes. At 11.5 the Imagon is a pretty sharp lens.

The 180mm Fuji covers 4x5 and the 200mm Imagon is for 6x9cm.

The 250mm Imagon is for 4x5 and the 250 Fuji covers 8 x 10.

The Imagon is a design that was developed and produced in the 1890's while the Fuji is much newer.

So the similarity ends with the fact that both use a disk.

4-Sep-2001, 16:30
Hi David,

I have a Fujinon SF 420 and a Rodenstock Imagon 360 for 8x10. As Bob has stated their precise differences, I will try to add a bit of hands-on. Both lenses produce excellent softness. The Imagon lens is controlled by its diffusion discs only, while the Fujinon SF uses a combination of diffusion discs (TWO discs marked as Yellow dot and red dot) and the aperture blades. There are three sets of aperture scales on the Fujinon lens for without disc, yellow disc, and red disc. The Fujinon SF is much easier to focus on a subject, sharper after f16 (not important here), and an IC of 500 mm. I still haven't figured out the best way to focus an Imagon without causing "focal plane migration". Hope this helps. Cheers,

Bob Salomon
4-Sep-2001, 17:52
" I still haven't figured out the best way to focus an Imagon without causing "focal plane migration". Hope this helps"


When an Imagon is sharply focused a spot of light forms a cross/

Also the focus of an Imagon changes with aperture so the Imagon must only be focused at taking aperture.

So the easiest way is to place a small, hi-intensity light at the subject and focus until the light forms a cross. When it does you are in focus. Remove the light and examine the ground glass to see what a properly focused Imagon looks like at that aperture. After doing this a few times you won't need the flashlight.

Also look for the smallest possible spectral. That is when you have best focus.

It is important to remember some things about the Imagon.

Don't use umbrellas. It wants/needs strong lighting. Use a 5:1 lighting ratio. It needs more contrast The Imagon will have greater DOF then a standard lens of the same aperture and focal length, take advantage of it.

2-Aug-2015, 03:48


Paul Ewins
2-Aug-2015, 04:46
Nice to know that the Fujinon SF 420 actually exists out in the real world and not just in the catalogs. I have seen plenty of the 180 and 250 but never a 420.

4-Aug-2015, 08:08