Carl Zeiss
Distagon 28mm f/2.8 T*
 

    Specifications

Number of elements: 7

Number of groups: 7

Max. aperture: f/2.8

Focal length: 28.5 mm

Negative size: 24 x 36 mm

Angular field 2w: diagonal 75º

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: 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22

Filter connection: clip-on-filter, diameter 59 mm

screw-in filter, thread M 55 x 0.75

Weight: approx. 280 g

Focusing range: infinite to 0.25 m

Entrance pupil:

Position: 22.9 mm behind the first lens vertex

Diameter: 10.0 mm

Exit pupil:

Position: 16.3 mm in front of the last lens vertex

Diameter: 19.3 mm

Position of principal planes:

H: 36.4 mm behind the first lens vertex

H': 9.4 mm in front of the last lens vertex

Back focal distance: 37.8 mm

Distance between first and last lens vertex: 54.0 mm
 

This Distagon lens for Contax 35 mm reflex cameras has been developed by Zeiss for all those who need a compact lens with an angular field of 74º and high image quality, but who do not require extremely high speed. This lens therefore meets the request voiced by many photographers for a lens with a relatively wide angular field and an initial aperture of f/2.8 which is perfectly adequate for most purposes. As the name Distagon® indicates, this is a lens where the distance between the last
lens surface and the film plane is longer than the focal length, allowing unobstructed motion of the reflex mirror.
This lens therefore belongs to the class of so-called retrofocus-type lenses. The lens is a full-fledged member of the Distagon® family and displays excellent image quality and remarkable image field illumination even at full aperture. The distance between the first and the last lens vertex is exceptionally short.
Like its sister lens with a focal length of 35 mm, the applications of this Distagon® lens are so varied that it can be described as a universal lens for all fields of photography.

Aperture    Real       ---------------- MTF ------------------
setting   aperture     Center(*)      Border(*)      Average(*)
--------------------------------------------------------------
2.8         -.1          8.4            6.6            7.7
4           +.1          8.8            7.6            8.3
5.6           0          8.8            7.8            8.5
8             0          8.6            7.9            8.4
11            0          8.3            7.7            8.1
16            0          7.7            7.0            7.5

22          +.3          6.9            6.4            6.7

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

MTF from www.zeiss.de