This lens is the widest rectilinear lens available for Pentax 6X7/67 system with the angle of coverage and perspective of 22mm lens on a 35mm camera. It is much smaller, lighter and more compact than any of the 55mm. This lens is a quite unique lens not only Pentax 6X7/67 system but in comparance to other ultra wide-angle lenses that cover 6X7. The most closest lens is rangefinder Mamiya 7 1:4.5 43mm which is the great performer but a bit darker and has serious light fall off from the center to the corners. Thus it requires using of dedicated center filter in many cases. The widest Mamiya RB/RZ67 lens is only 50mm and is slightly darker by 1/2 EV.

This is one of few lenses that have special clip on the rear side to hold slip-in gelatin filters.

Variants

There are two variants of the same lens were produced. It is exactly the same lens. The difference is only in the name engraved on the lens, focusing and aperture rings finishing.

Pentax 67 1:4 45mm - Two generations of the same lens

Two generations of the same lens

Focusing and aperture rings finishing difference

Focusing and aperture rings finishing difference

Lens nameWeightYear
SMC PENTAX-6X7 1:4 45mm486g1980
SMC PENTAX 67 1:4 45mm486g1989

Filters

The lens accepts special 6X7 bayonet filters as well as screw-in filters of 82mm size. It is also has a special clip on the rear side to mount slip-in gelatin filters. Using such filters allows to prevent result image from vignetting.

45mm f/4. Bayonet and screw-in filters mount

Bayonet and screw-in filters mount

Rear view of the lens showing clip for the slip-in gelatin filters

Rear view of the lens showing clip for the slip-in gelatin filters

Aperture

The diaphragm unit of the lens has 8 aperture blades. Each of the images below shows aperture consequentially stopping down by 1EV.

Hood

The early version of the original dedicated hood has "6X7" sign and lens parameters engraved on the top. Later Pentax has changed it to "PH-SB" model name. These hoods are the same. They both have very good internal blackening preventing lens from reflections good enough.

Early "6X7" hood

Early "6X7" hood

45mm f/4 Late "PH-SB" hood

Late "PH-SB" hood

45mm f/4  Late "PH-SB" hood showing clip-on mount

Late "PH-SB" hood showing clip-on mount

A cheap round metal hood can be found on eBay for just $4. It is a good solution because original dedicated hood costs around $60 for the hood with case. In other hand the orginal hood has better internal blackening that the cheap one lacks.

45mm f/4 Cheap 82mm metal round hood

Cheap 82mm metal round hood

Lens data

45mm f/4 formula

45mm f/4 formula

  • Focal length: 45mm
  • 35mm equivalent: 24mm
  • Optical formula: 9 elements, 8 groups
  • Field of view: 89°
    • Horizontal: 76°
  • Mount: inner bayonet
  • Diaphragm: automatic
    • Aperture range: 4 ~ 22
    • Aperture blades: 8
  • Close distance: 37cm
    • Magnification: 0.17×
    • Picture area: 324×412mm
  • Filter: 82mm - screw-in and bayonet
  • Hood: PH-SB 82mm
  • Case: S90-100
  • Dimensions: 91.5×57.5mm