Minolta AF 500mm Reflex lens
Encyclopedia
Originally produced by Minolta
, and until recently, produced by Sony
, the AF 500mm Reflex is a catadioptric photographic lens
compatible with cameras using the Minolta AF
and Sony α lens mount
s.
The Minolta/Sony 500mm Reflex lens is the only production mirror lens designed to auto focus
with an SLR camera. There are other mirror lenses that can mount onto current mounts such as Canon EF-mount
and Nikon F-mount
but all of these mirror lenses are manual focus
only. Only this lens can have its focus controlled by the camera's autofocus
motor in conjunction with TTL
autofocus sensing. In terms of the Minolta AF and subsequent Sony α SLR systems, this lens is an anomaly, being the only lens able to auto focus at 8 (with the exception of this lens, all other AF lenses must be 6.3 or larger for AF to function).
The mirror design does not utilize aperture blades, and thus the aperture
of the lens is fixed at 8. Exposure may only be controlled by shutter
speed, film or sensor sensitivity, or a rear mounted neutral density filter
.
By using a mirror design similar to that of a telescope
, this lens uses very little glass compared to traditional telephoto lens
es and is thus much smaller, lighter, and far less expensive than traditional lenses in the same focal length
. However, this and all other mirror lenses can produce an undesirable donut shaped bokeh
in the image it produces.
Minolta
Minolta Co., Ltd. was a Japanese worldwide manufacturer of cameras, camera accessories, photocopiers, fax machines, and laser printers. Minolta was founded in Osaka, Japan, in 1928 as . It is perhaps best known for making the first integrated autofocus 35mm SLR camera system...
, and until recently, produced by Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
, the AF 500mm Reflex is a catadioptric photographic lens
Photographic lens
A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.While in principle a simple convex lens will suffice, in...
compatible with cameras using the Minolta AF
Minolta AF
The Minolta Alpha camera system was a collection of photographic equipment from Minolta. The system used a lens mount called A-mount, with a flange focal distance 44.50 mm. The new mount was larger than the older SR-mount making old manual lenses incompatible with the new system...
and Sony α lens mount
Lens mount
A lens mount is an interface — mechanical and often also electrical — between a photographic camera body and a lens. It is confined to cameras where the body allows interchangeable lenses, most usually the single lens reflex type or any movie camera of 16 mm or higher gauge...
s.
The Minolta/Sony 500mm Reflex lens is the only production mirror lens designed to auto focus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
with an SLR camera. There are other mirror lenses that can mount onto current mounts such as Canon EF-mount
Canon EF lens mount
Introduced in 1987, the EF lens mount is the standard lens mount on the Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens...
and Nikon F-mount
Nikon F-mount
The Nikon F-mount is a type of interchangeable lens mount developed by Nikon for its 35 mm SLR cameras. The F-mount was first introduced on the Nikon F camera in 1959, and features a three lug bayonet mount with a 44 mm throat and a flange to focal plane distance of 46.5 mm...
but all of these mirror lenses are manual focus
Manual focus
In the field of photography, a manual focus camera is one in which the operator has to adjust the focus of the lens by hand. Before the advent of autofocus, all cameras had manually adjusted focusing; thus, the term is a retronym....
only. Only this lens can have its focus controlled by the camera's autofocus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
motor in conjunction with TTL
Through-the-lens
Through-the-lens metering is a photographic term describing a feature of cameras capable of measuring light levels in a scene through their taking lenses, as opposed to a separate metering window...
autofocus sensing. In terms of the Minolta AF and subsequent Sony α SLR systems, this lens is an anomaly, being the only lens able to auto focus at 8 (with the exception of this lens, all other AF lenses must be 6.3 or larger for AF to function).
The mirror design does not utilize aperture blades, and thus the aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
of the lens is fixed at 8. Exposure may only be controlled by shutter
Shutter (photography)
In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor to light to capture a permanent image of a scene...
speed, film or sensor sensitivity, or a rear mounted neutral density filter
Neutral density filter
In photography and optics, a neutral density filter or ND filter can be a colorless or grey filter. An ideal neutral density filter reduces and/or modifies intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition.The purpose of standard photographic...
.
By using a mirror design similar to that of a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
, this lens uses very little glass compared to traditional telephoto lens
Telephoto lens
In photography and cinematography, a telephoto lens is a specific type of a long-focus lens in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special lens group known as a telephoto group that extends the light path to create a long-focus...
es and is thus much smaller, lighter, and far less expensive than traditional lenses in the same focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
. However, this and all other mirror lenses can produce an undesirable donut shaped bokeh
Bokeh
In photography, bokeh is the blur, or the aesthetic quality of the blur, in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light."...
in the image it produces.