A rare ZOMZ 28mm f/6 Topogon-type wide-angle for the Contax/Kiev external bayonet, using scale focusing without rangefinder coupling.
ZOMZ Orion-15 28mm f/6 (Contax RF)
Contax RF mount
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The ZOMZ Orion-15 28mm f/6 (Contax RF) is a Contax RF-mount lens for Leica rangefinder cameras. Leica price index →
Specification
About this lens
ZOMZ Orion-15 28mm f/6 (Contax RF)
The ZOMZ Orion-15 28mm f/6 (Contax RF) is the uncommon production version made for Contax and Kiev rangefinder cameras. It uses a symmetrical four-element, four-group Topogon-type optical construction in a compact aluminum barrel.
The lens mounts on the external Contax/Kiev bayonet and contains its own focusing helicoid and distance scale. Unlike the M39 Orion-15, the production Contax/Kiev version does not operate the camera's rangefinder. It must be scale focused from 1m to infinity.
The bayonet version also has its own physical specifications. Published technical data give a 34mm length, approximately 53.5mm maximum barrel diameter and a 49mm front accessory thread. These values should not be copied from the smaller M39 barrel, which uses a different registration distance and front fitting.
Production examples are documented with a seven-blade continuously adjustable diaphragm. One compiled technical sheet gives six blades, but direct examination of ZOMZ bayonet examples records seven. Seven is therefore used for this production profile.
The Contax/Kiev Orion-15 uses the external bayonet, an independent focus ring and scale focusing without rangefinder coupling. Its four-element, four-group symmetrical construction prioritises compactness and restrained distortion over speed. The 34mm length, 53.5mm diameter and 49mm accessory fitting belong to this bayonet barrel and should not be copied from the smaller coupled M39 version.
Optical qualities
Rendering
The Orion-15 emphasizes depth of field, compactness and low geometric distortion rather than speed or subject isolation. Its f/6 maximum aperture makes scale focusing practical in daylight.
Sharpness
Period specifications indicate strong central resolution and lower but useful edge resolution. Performance improves across the field when stopped down, although copy condition and optical alignment remain important.
Contrast and flare
The optical surfaces are single coated. Contrast can be good with clean glass, but flare resistance is limited compared with later multicoated lenses. Internal haze and cleaning damage can noticeably reduce performance.
Distortion and vignetting
The symmetrical Topogon-type construction provides restrained distortion. Illumination falloff is more apparent near maximum aperture, particularly in evenly toned subjects.
At maximum aperture
Maximum-aperture performance should be evaluated with a correctly calibrated camera. A coupled rangefinder measures distance through a mechanical cam and does not inspect the image plane directly. Small errors in the body, mount or lens can therefore shift the sharp plane. Subject movement and field curvature may also be mistaken for optical softness. A clean, properly assembled lens should be tested at several distances before conclusions are drawn.
The widest setting provides the greatest light transmission and the least depth of field available from the design. Contrast can be reduced by residual aberrations, internal reflections or aged coatings. Bright point sources may show glow or flare. These effects vary between examples and should not be presented as a fixed signature of every surviving lens.
Stopped down
Closing the diaphragm increases depth of field and generally improves consistency across the 35mm frame. Middle apertures are often the practical choice for documentary work, landscapes and architecture. The smallest aperture provides more depth but is not automatically the sharpest setting because diffraction gradually reduces fine contrast.
Aperture shape depends on blade count and mechanical condition. Oil, bent blades or an incorrectly assembled iris can change both operation and out-of-focus highlights. Published blade counts should remain tied to the exact barrel version rather than copied between mounts.
Handling and compatibility
Contax and Kiev rangefinder lenses use either the internal standard-lens bayonet or the external bayonet. These interfaces serve different mechanical purposes even though they belong to the same camera system. Similarity to Nikon S or another rangefinder mount does not guarantee correct registration, coupling or infinity focus. A suitable adapter must reproduce the required focusing mechanism and keep the rear assembly clear of internal camera parts.
Historical lenses should not be judged from one sample alone. Haze, fungus, separation, cleaning damage, displaced elements and dried lubricant can alter contrast and focus more than modest design differences. Film choice, processing, digital sensor cover glass and adapter tolerances also influence results. A hood may reduce oblique flare but cannot correct internal contamination.
History
Development and Launch
The Orion-15 design originated in GOI wide-angle research. Early prototype and pre-series Contax/Kiev examples were produced before the regular consumer versions appeared.
Production Evolution
KMZ produced early prototypes and pre-series versions. The production Contax/Kiev lens covered by this profile was manufactured in small quantities by ZOMZ from approximately 1964 through 1974. It is mechanically distinct from the coupled M39 version.
Special Editions/Variants
Early GOI and KMZ prototype versions should not automatically be grouped with the later ZOMZ production lens. Sovietcams also documents a privately modified internal-bayonet example, which is not a factory production variant.
Collector Notes
Confirm the external Contax/Kiev bayonet, independent focus ring and absence of a rangefinder linkage. The M39 version is visually similar but uses a threaded mount, different barrel measurements and functional rangefinder coupling.
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