Cut and paste my interpretation of the instructions for using a Mamiya 645 145mm f4.0 soft Focus lens (ex-dpr)
I had thought that my lens had a fault in the way it worked but on close reading of the instruction manual supplied by Mamiya I have discovered that the lens is working as designed (for a Mamiya Camera Body)
In order to provide some help to others who might decide to use one of these complex lenses I am reproducing a subset from the manual with some of my own obesrvations as regards to use on digital bodies.
Operation of Mamiya-Sekor SF C 145mm f4.0 lens (Soft Focus ) M645 Mount
Lens instructions for use on a Mamiya 645 body (subset from instructions booklet)
Note: see addendum “Difficulties when used adapted to digital camera bodies”
Adjustment of the Soft-Focus Effect
1. Softness Control Ring
There are five circles of different colours on the Softness Control Ring. The sizes of these coloured circles indicate the degree of softness produced at that setting. The soft-focus effect is maximum when the largest circle (orange) is set at the red index mark in the centre. And the effect is minimum when the smallest circle (blue) is set at the index mark. The degree of softness can also be varied continuously by setting at any place between the circles.
2. Aperture Ring
The degree of softness is also affected by changing the aperture. The soft-focus effect is maximum at f/4 and decreases as the lens is stopped down. Intermediate aperture settings can also be used. When the smallest circle (blue) is set at the index mark, the soft-focus effect completely disappears at f/8 or smaller apertures. The soft-focus effect can be varied continuously over a wide range by combining the Softness Control Ring and Aperture Ring settings.
How to Focus
When the Focusing Ring of this lens is pulled toward the camera, it automatically stops down to an aperture where focusing is easy (f8.0 in A mode)*.
How to Take Pictures
1. Set the A-M selector lever of the lens to A (auto) **.
2. Rotate the Softness Control Ring and Aperture Ring until the desired degree of softness is obtained.
3. Pull the Focusing Ring fully toward the camera and rotate it to focus accurately. (closes aperture to f8.0 only)
4. After focusing, remove the fingers from the Focusing Ring. It will automatically return to its original position and the aperture will open fully. (this is f4.0 and action will toggle between f8.0 and f4.0 only)
(Exposure will not be correct if the shutter is released with the Focusing Ring pulled toward the camera because the lens will stop down to the smallest aperture regardless of the setting. *** (to be held open on a digital camera body will result in the image being taken at f8.0)
5. Determine the correct exposure values and set the shutter speed; then release the shutter when ready.
It is necessary to refocus each time the Softness Control Ring is rotated to adjust the degree of softness. This is not necessary when the softness is adjusted using the Aperture Ring.
To check the degree of softness or the depth-of-field before making an exposure, set the A-M Selector Lever to M (manual) ** and adjust the aperture ring while watching the subject through the viewfinder. (This presently seems to be the only logical way to use this lens to best advantage on a digital camera body)
When focusing with the lens set to M (manual), set the aperture ring to f/8 (less soft focus) With these settings, do not pull the focusing ring toward the camera. The lens will stop down to the smallest aperture regardless of the aperture setting.***
Distance Scale
Rotating the Softness Control Ring varies both the focal length of the lens and the distance at which it is focused; therefore, distance scale index marks in colours corresponding to those of the five circles are placed in accordance with the amount the focused distance changes.
The colour of the index mark used corresponds to the colour of the circle at which the Softness Control Ring is set. For example, when the large orange circle is set at the red index mark in the centre, as shown in the photograph, the focused distance is indicated by the orange index mark to be 3m (approx. 9ft.). If the Softness Control Ring is then rotated so that the blue circle is set at the centre red index mark, without moving the Focusing Ring, the focused distance will be 00 (infinity) as indicated by the blue index mark.
When the Focusing Ring is set at the closest possible distance, the blue index mark indicates 1.5m (approx. 5 ft.). The other index marks will indicate closer distances, but this lens focuses only from 1.5m to infinity so the soft-focus effect is available only at the blue circle in this case.
Conversely, when the Focusing Ring is set at the maximum possible distance, the orange index mark indicates infinity while the others indicate in excess of infinity. When the Softness Control Ring is to be used at any of the other positions, the index mark of the same colour must be set at the mark to focus the lens at infinity. Be sure to check through the viewfinder for accurate focusing.
How to Use as a Normal Lens
To take sharp pictures without any soft-focus effect with this lens, set the small blue circle at the red centre index mark and stop the lens down to f/8 or more.
The Soft-Focus Effect
As described above, the soft-focus can be continuously varied by rotating the Softness Control Ring and Aperture Ring. There are also subtle differences in accordance with the focused distance, contrast between subject and background, lighting, degree of enlargement, print density, whether colour or black and white, etc. These must therefore be considered in order to obtain a suitable degree of soft-focus effect.
Difficulties when used adapted to digital camera bodies
* When in A mode on release of focus aperture the lens will only move to wide open (f4.0) irrespective of set aperture for proposed capture and lens auto stopped down of f8.0 aperture to overcome effect of soft focus and assist accurate focusing.
If used in M mode the lens will not auto resume preset capture aperture if greater than f8 or less but return to the f8 or lower value preset. If set to f8.0 or less it will stop down further for focus and return to the preset aperture of f8.0 or less when the focus ring action is released. It will not auto return to f5.6 or f4.0 and therefore cannot automatically achieve the higher levels of soft focus.
** The Fotodiox adapter I have has a fixed extension lever inside which automatically disables A mode and the lens works in M mode no matter in what position the mode switch on the lens is set. This lever technically seems only useful for such lenses that may not have a mode switch on the lens body. However A mode only works f8.0 and f4.0 apertures therefore I propose to simply work within the limitations of M mode only.
*** This seems to be related to its use on a Mamiya camera body only.
