Carl Zeiss
Planar 50mm f/1.7 T*
 

            Specifications

Number of elements: 7

Number of groups: 6

Max. aperture: f/1.7

Focal length: 51.9 mm

Negative size: 24 x 36 mm

Angular field 2w: diagonal 47º

Mount: focusing mount with bayonet;

TTL metering either at full aperture or in stopped-
          down position.

Aperture:  priority/Shutter priority/Automatic
          programs (Multi-Mode Operation)

Aperture scale: 1.7 - 2.8 - 4 - 5.6 - 8 - 11 - 16

Filter connection: clip-on-filter, diameter 57 mm

screw-in filter, thread M 55 x 0.75

Weight: approx. 195 g

Focusing range: infinite to 0.6 m

Entrance pupil:

Position: 22.9 mm behind the first lens vertex

Diameter: 30.4 mm

Exit pupil:

Position: 28.9 mm in front of the last lens vertex

Diameter: 41.0 mm

Position of principal planes:

H: 34.5 mm behind the first lens vertex

H': 13.7 mm in front of the last lens vertex

Back focal distance: 38.2 mm

Distance between first and last lens vertex: 39.6 mm
 

For the Contax® owner this lens is an attractively priced alternative to the fast 50 mm f/1.4 standard lens. The relative aperture of 1:1.7 is absolutely sufficient for many photographic purposes.
The image quality is excellent and can even be compared with that of the 50 mm Planar® f/1.4 lens at the corresponding f-stops. Specific mention should be made of the relatively short design and the low weight of this high-performance seven-element lens.

Aperture    Real       ---------------- MTF ------------------
setting   aperture     Center(*)      Border(*)      Average(*)
--------------------------------------------------------------
1.7         -.2          8.0            6.0            6.9
2.8           0          9.0            7.4            8.3
4             0          9.1            8.0            8.7
5.6           0          9.0            8.4            8.8
8           +.1          8.7            8.4            8.6
11            0          8.3            8.1            8.3
16          +.2          7.7            7.7            7.7

(*) = (3=poor, 5=sufficient, 7=good, 9=excellent)

MTF from www.zeiss.de