Data sheet: Mamiya CS 50 mm f/1.7 (NC/CS mount)

Pekka Buttler, 07/2024

Pictured: Auto Mamiya-Sekor CS 50 mm f/1.7


The table below summarizes the lens’ key specifications (measurements based on pictured sample):

Brand:Mamiya-SekorLens nameCS 1:1.7 f=50mm
Focal length(s)150 mmAngle-of-view246,8°
Maximum Aperturef/1.7In Production1977-1980
Lens mountMamiya NC/CSSubfamily (if applicable)––
Length332,0 mmDiameter461,1 mm
Filter ring diameter49 mmWeight145 grams
Lens element count6Lens group count5
Aperture blades (S/R/C)56 SFocus throw210 °
Minimum focusing distance45 cmsMaximum magnification1:6,9
Has manual aperture ringYESHas Manual focus ringYES

Further notes:

• In 1977 Mamiya introduced the NC1000 line of cameras and lenses.
• For the NC1000 camera, Mamiya introduced 14 lenses, including four 50 mm lenses: one f/3.5 macro lens, as well as regular 50 mm lenses with the maximum apertures of f/2, f/1.7 and f/1.4 respectively. Hence, while slower than the f/1.4, this f/1.7 lens was not the ‘budget fifty’ offering.
• With its 49 mm filter thread and compact size, this lens is a typical example of late manual era nifty fifties.
• The aperture mechanism of Mamiya NC/CS lenses is auto-only, meaning that the aperture ring never directly controls the aperture diaphragm. Instead, the aperture ring sets the value to which the aperture will be closed down when the camera actuates the lens’ aperture stop-down pin.


This lens was in production for only ≈4 years, and it has no direct predecessor, as this was Mamiya’s first 50 mm f/1.7 lens. However, it is closely related to its successor, the Mamiya-Sekor E 50 mm f/1.7 (Z/E mount)

History of Mamiya NC/CS lenses

Please see the JAPB article on all (7) Mamiya SLR lens mounts to understand the role of the Mamiya NC/CS mount .


n.B! The following applies to all Mamiya NC/CS mount lenses.

This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need a Mamiya NC1000 or NC1000s film body. While the Mamiya NC/CS system was quickly overtaken by events, the cameras themselves were thoughtfully designed and well-made and many remain perfectly serviceable today. Alternatively, you can use most of the features of the lens on a Mamiya ZE or ZE-2 body (these early Mamiya Z/E system bodies have the ability to both mount Mamiya NC/CS lenses and activate their aperture mechanism. See more, in the JAPB article on all (7) Mamiya SLR lens mounts).

While Mamiya NC/CS lenses are otherwise straightforward and purely mechanical, they need the camera body (or adapter) to depress the aperture stop-down pin for the aperture ring to have any significance.

Therefore, should you aim to adapt this lens to a mirrorless camera you will need an adapter that facilitates adjusting the lens’ aperture. Luckily, every Mamiya NC/CS adapter I’ve seen does offer such a functionality. However, due to Mamiya NC/CS lenses not being among the most numerously manufactured, special adapters (helicoid adapters, tilt/shift adapter and speed boosters) are currently unavailable and adapter availability can generally not be taken for granted.

Using Mamiya NC/CS lenses on dSLRs is also theoretically possible. However, due to that the, difference in flange focal distances between the Mamiya NC/CS lens and the dSLR mount (between +1,5 mm and negative 1 mm) invariably does not allow sufficient space for an adapter that allows aperture modification, these adapters are always adapters with added optics to achieve infinity focus.

Importantly, while you can mount Mamiya NC/CS lenses on Mamiya Z/E system adapters, these adapters will not allow you to change the lens’ aperture.


  1. Focal length is (unless stated otherwise) given in absolute terms, and not in Full-frame equivalent. For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’. ↩︎
  2. Picture angle is given in degrees (based on manufacturers’ specs) and concerns the diagonal picture angle. Rule of thumb:
    > 90 ° ==> Ultra-wide-angle
    70–90 ° ==> Wide-angle
    50–70 ° ==> Moderate wide-angle
    40–50 ° ==> ‘Standard’ or ‘normal’ lens
    20–40 ° ==> Short tele lens
    10-20 ° ==> Tele lens
    5-10 ° ==> Long tele lens
    < 5 ° ==> Ultra-tele lens ↩︎
  3. Length is given from the mount flange to the front of lens at infinity. ↩︎
  4. Diameter excludes protrusions such as rabbit ears or stop-down levers. ↩︎
  5. S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎

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