Avenon's compact fast ultra-wide — the 21mm f/2.8 in Leica Thread Mount.
The Avenon 21mm f/2.8 in Leica Thread Mount is a compact Japanese ultra-wide from around 1994, made by Kobayashi Seiki and sold under the Avenon name. It is a modern screw-mount wide-angle from the mid-1990s, produced for L39 and adapted rangefinder bodies as a relatively fast 21mm in a small package.
It is a manual-focus rangefinder-coupled lens with a 21mm focal length and a maximum aperture of f/2.8, brighter than many compact wides of its class. Framing uses a 21mm accessory finder since rangefinder bodies do not show this field, and depth of field at this focal length is deep.
At 21mm the lens takes in wide landscapes, interiors and street scenes with a mostly rectilinear view, and the f/2.8 aperture gives more flexibility than slower ultra-wides. Stopping down to f/8 gives broad depth of field and tidy corners for architecture and travel.
As a relatively modern lens, used copies are generally mechanically sound; check for clear glass, smooth focus and a positive aperture, plus any haze or cleaning marks. It adapts to Leica M with an LTM-to-M ring and to mirrorless cameras via a simple adapter, where corner colour cast can appear and a matching finder or the screen handles framing.