OLYMPUS F. Zuiko lens; 35mm f/2.8 for XA.     Tested November 1979.

Lens number not given; integral camera number 125475.                  


Specifications: Non-interchangeable 35mm f/2.8 F. Zuiko (un-numbered), apertures to f/22, focusing to 2.8ft., does not accept front-mounted accessories. Has electronically-controlled leaf shutter between lens elements.

Optical construction Six-element, five-group optic best described as a reversed retro-focus wide-angle lens which has been modified to shorten its overall length (approximately 31mm from front element to film plane) compared to its focal length, in a manner resembling that of a true telephoto.

It has large rear elements to enable coverage of the 24 x 36mm negative, and for rigidity as well as shallow depth, it uses internal focusing (by moving the third optical group back and forth). High refractive-index glasses were used to control aberrations across the picture field, and manufacturing tolerances were very tight.

                    RESOLUTION

OLYMPUS ZUIKO 35mm f/2.8
at 1:53 magnification
f/no. Center
(Lines/mm) 		Corner
(Lines/mm)
2.8 Acceptable 42 Good 30
4 Good 47 Good 32
5.6 V. Good 59 V. Good 42
8 Excellent 67 Excellent 47
11 Excellent 67 Excellent 53
16 Excellent 59 Excellent 47
22 Good 47 V. Good 37
                      CONTRAST

OLYMPUS ZUIKO 35m f/2.8
at 30 lines / mm
f/no. Center
( % ) 		Corner
( % )
2.8 Low 38 Medium 29
4 Low 52 Medium 34
5.6 Low 56 Low 42
8 Low 60 Low 42
11 Medium 58 Medium 38
16 Medium 56 V. Low 24
22 Medium 60 V. Low 24


Practical comments: None provided.

Optical bench analysis On axis at full aperture, yellow flare was visible, along with very slight over-corrected spherical aberration. Flare was nearly gone by f/4. Off axis, yellow-green flare was evident at full aperture but greatly improved by f/5.6. Very slight lateral color and very slight astigmatism persisted to f/8.

Field test slides: At full aperture, images were adequately sharp but ample flare could be seen in any bright objects particularly those with highlights. However by f/5.6 the flare disappeared completely and images were impressively crisp and snappy. Pictures made with flash did show some slight edge falloff when the backgrounds were of an even tone, and the exposures were generally about ½ f/stop on the deeper, rich underexposure side which many people do prefer. (November 1979).

Modern's Photo Buying Guide '85
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