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Abbreviations

Specification

Sources of data

• Manufacturer's technical data.
• Interchangeable lenses for Mamiya RB67 instructions.
• Mamiya interchangeable lenses for Mamiya RB67 Professional instructions.
• The photograph. Mamiya RB67 Pro S booklet.
• Mamiya RB67 Pro-S booklet.
• Mamiya RB67 Pro-SD system accessories chart.
• Mamiya RB67 Pro-SD booklet (2 ED., PUB. 2112).
• Mamiya medium format cameras booklet.
• Mamiya medium format cameras booklet (PUB. 9012).
• Mamiya medium format cameras booklet (PUB. 9022).
• Mamiya RB67 Pro-SD booklet (13 ED., PUB. 2112).

Manufacturer description #1

The variable diffusion 150mm f/4 lens is an open diaphragm soft focus lens that deliberately produces a beautiful flare. Several interchangeable diaphragms are available, including a honeycomb diaphragm, and it is possible to vary the flare by adjusting the aperture. It is ideal for portraits that are intended to convey a particular mood and for general special effects photography. Since it corresponds to the 35mm format 75mm lens, its picture angle permits it to be used even in small studios.

Manufacturer description #2

Mamiya’s long experience and concentrated technology have made possible the development of the all new Mamiya-Sekor SF C 150mm f/4 Soft Focus Lens. A special type of spherical aberration has been purposely introduced into this lens to produce photographic images that are sharp yet which have an alluring softness. And the highly advanced design using 3 new types of optical glass has made possible extremely precise correction of all other types of aberrations as in standard lenses as well as superb color balance.

The soft focus effect is eliminated when this lens is stopped down to f/8 or more so the same sharp images obtained with standard lenses are available when desired. And the soft focus effect can be varied at will by using the three different Softness Control Discs provided with the lens.

There are three different types of Softness Control Discs, each with a different diameter hole in the center. Always set this lens at full aperture (f/4) when using one of the Softness Control Discs. The f-value of this lens changes according to the Disc used. When the No. 1 Disc is used the effective lens aperture is approximately f/5; for the No. 2 Disc this value is approximately f/5.6; and for the No. 3 Disc it is approximately f/6.3.

The special spherical aberration used in this lens to produce the soft focus effect causes some discrepancy in focusing when this is done at full aperture; therefore, when focusing always stop this lens down to at least f/8 to cancel the soft focus effect.

Manufacturer description #3

The 150mm f/4.0 is a unique, special application lens offering variable soft focus and use as a normal application telephoto at smaller apertures. It is the prime lens for many portrait and wedding photographers because of its unusual and controllable soft focus effects using designed-in spherical abberation at apertures from f/4 to f/8 and a set of three diffusion discs. The combination creates soft focus images that appear sharp at the same time, eliminating the need for costly and time consuming retouching. At f/8 and smaller apertures, it renders completely sharp, normal images. Its 150mm focal length makes it ideal for small studio working distances. Applications include portraiture, fashion, beauty, landscape and general photography.

Mamiya-Sekor C series

The second generation of lenses designed for Mamiya RB67 series medium format 6x7 SLR cameras. Introduced with the Mamiya RB67 Professional S in 1974.

• New barrel design;
• Mechanical Seiko #1 leaf shutter;
• Fully synchronized for M- and X-settings so that you can work with flash at all shutter speeds;
• Fully automatic diaphragm;
• Multi-layer anti-reflection coating;
• Standardized 77mm filter thread mount for optimized handling with accessories (except the 37/4.5 fisheye and 500/8 lenses).

Frequently asked questions

Other short telephoto prime lenses in the Mamiya RB67 system