A secondary lens may be designed to be used either in front of the primary lens, between it and the subject, or behind the primary lens, between it and the film.
Secondary lenses are typically simpler in mechanical design than other photographic lenses. Normally but not always there is no provision for control of focus or aperture, as these are achieved by the controls on the primary lens.
Lenses used in front of the primary lens
Examples of secondary lenses designed to be used in front of the primary lens are:
The most common secondary lens used behind the primary lens is the teleconverter. A typical teleconverter has a male and a female lens mount of the same type, to allow it to be used between a primary lens and a camera body of the matching system. The resulting combination has a greater focal length than the primary lens alone, and the same absolute aperture, so its f-number is increased accordingly.
Some teleconverters are dedicated or matched to particular primary lenses, normally one or more lenses by the same manufacturer as the teleconvertor, and when used in this combination deliver quality comparable to the primary lens. Others are general-purpose, and in use typically offer less image quality then a primary lens of the same quality, but allow a camera kit to offer a wider variety of focal lengths with a smaller number of lenses, saving in both cost and weight.
It is not normally possible to construct a similar wide-angle adaptor, as the angle of view of the primary lens is matched to the film format for which is designed, and unwanted light is typically stopped by baffles. Any device similar to a teleconverter designed to use the primary lens for wider angles than those for which it is designed is therefore likely to cause vignetting. Focal reducers are an exception which take advantage of focal flange difference between camera systems.
Cross-system adaptors
Specialised secondary lenses may be used behind the primary lens to adapt a lens of one camera system and/or film format to another. These are called active adaptors or converters. For example, a Pentax screw mount lens cannot normally be mounted on a Nikon F-mount camera, as the Nikon bayonet mount is further from the film plane than the Pentax screw mount, leaving no room for a mount adaptor. However active adaptors are available containing a (not very powerful) teleconverter, which makes the combination mechanically possible, albeit with a small amount of cropping at the image edges and loss of connection of the camera to any lens automation.
The optical components of these adaptors may reduce or increase the focal length of the combination, or they may affect only the back focal distance of the combination, leaving the effective focal length for purposes of photographic composition unchanged.
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.
A fisheye lens is an ultra wide-angle lens that produces strong visual distortion intended to create a wide panoramic or hemispherical image. Fisheye lenses achieve extremely wide angles of view, well beyond any rectilinear lens. Instead of producing images with straight lines of perspective, fisheye lenses use a special mapping, which gives images a characteristic convex non-rectilinear appearance.
In film and photography, a prime lens is a fixed focal length photographic lens, typically with a maximum aperture from f2.8 to f1.2. The term can also mean the primary lens in a combination lens system. Confusion between these two meanings can occur without clarifying context. Alternate terms, such as primary focal length, fixed focal length, or FFL are sometimes used to avoid ambiguity.
The Pentax Auto 110 and Pentax Auto 110 Super were fully automatic single-lens reflex cameras manufactured by Asahi Pentax for use with Kodak 110 film cartridges. The Auto 110 was introduced with three interchangeable, fixed focal length lenses in 1978. A further three lenses were added in 1981 to coincide with the release of the Auto 110 Super the following year. The camera system was sold until 1985. The complete system is sometimes known as the Pentax System 10, apparently for its official Pentax name, although most Pentax advertising only uses the camera name or Pentax-110. This model represented the only complete ultraminiature SLR system manufactured for the 110 film format, although several fixed-lens 110 SLRs were sold. The camera system also claims to be the smallest interchangeable-lens SLR system ever created.
A digital single-lens reflex camera is a digital camera that combines the optics and mechanisms of a single-lens reflex camera with a solid-state image sensor and digitally records the images from the sensor.
A lens mount is an interface – mechanical and often also electrical – between a photographic camera body and a lens. It is a feature of camera systems where the body allows interchangeable lenses, most usually the rangefinder camera, single lens reflex type, single lens mirrorless type or any movie camera of 16 mm or higher gauge. Lens mounts are also used to connect optical components in instrumentation that may not involve a camera, such as the modular components used in optical laboratory prototyping which join via C-mount or T-mount elements.
A teleconverter is a secondary lens mounted between a camera and a photographic lens which enlarges the central part of an image obtained by the lens. For example, a 2× teleconverter for a 35 mm camera enlarges the central 12×18 mm part of an image to the size of 24×36 mm in the standard 35 mm film format.
A full-frame DSLR is a digital single-lens reflex camera (DSLR) with a 35 mm image sensor format. Historically, 35 mm was one of the standard film formats, alongside larger ones, such as medium format and large format. The full-frame DSLR is in contrast to full-frame mirrorless interchangeable-lens cameras, and DSLR and mirrorless cameras with smaller sensors, much smaller than a full 35 mm frame. Many digital cameras, both compact and SLR models, use a smaller-than-35 mm frame as it is easier and cheaper to manufacture imaging sensors at a smaller size. Historically, the earliest digital SLR models, such as the Nikon NASA F4 or Kodak DCS 100, also used a smaller sensor.
The Nikon DX format is an alternative name used by Nikon corporation for APS-C image sensor format being approximately 24x16 mm. Its dimensions are about 2⁄3 those of the 35mm format. The format was created by Nikon for its digital SLR cameras, many of which are equipped with DX-sized sensors. DX format is very similar in size to sensors from Pentax, Sony and other camera manufacturers. All are referred to as APS-C, including the Canon cameras with a slightly smaller sensor.
This article details lensesfor single-lens reflex and digital single-lens reflex cameras. The emphasis is on modern lenses for 35 mm film SLRs and for "full-frame" DSLRs with sensor sizes less than or equal to 35 mm.
In photography, the 35 mm equivalent focal length is a measure of the angle of view for a particular combination of a camera lens and film or image sensor size. The term is popular because in the early years of digital photography, most photographers experienced with interchangeable lenses were most familiar with the 35 mm film format.
The Micro Four Thirds system is a standard released by Olympus Imaging Corporation and Panasonic in 2008, for the design and development of mirrorless interchangeable lens digital cameras, camcorders and lenses. Camera bodies are available from Blackmagic, DJI, JVC, Kodak, Olympus, OM System, Panasonic, Sharp, Logitech Mevo and Xiaomi. MFT lenses are produced by Cosina Voigtländer, Kowa, Kodak, Mitakon, Olympus, Panasonic, Samyang, Sharp, Sigma, SLR Magic, Tamron, Tokina, TTArtisan, Veydra, Xiaomi, Laowa, Yongnuo, Zonlai, Lensbaby, Venus Optics and 7artisans amongst others.
The design of photographic lenses for use in still or cine cameras is intended to produce a lens that yields the most acceptable rendition of the subject being photographed within a range of constraints that include cost, weight and materials. For many other optical devices such as telescopes, microscopes and theodolites where the visual image is observed but often not recorded the design can often be significantly simpler than is the case in a camera where every image is captured on film or image sensor and can be subject to detailed scrutiny at a later stage. Photographic lenses also include those used in enlargers and projectors.
Pentax lenses were first badged as Takumar. The Takumar branded lenses were well respected for their line of Super Takumar, which designated the high performance coating applied to the lens as well as the optical formulas used to make them. The majority of the industry at the time was still satisfied with the variations of the "plumb" coating process and later some of the two and three layer processes as well. Asahi Pentax soon introduced the Takumar Super-Multi-Coated line of lenses which was a 7 layer process as the industry had just caught up with similar forms of 5 layer multi-coated optics. Eventually Asahi Optical and Pentax slowly shifted much of their lens production under the Pentax name and transitioned some of the successful designs that were first introduced under the Takumar name to use Asahi/Pentax badging as well as beginning to use the "smc" abbreviation. Eventually the Asahi partnership disappeared and the Pentax name became solely used. Pentax lenses saw many feature changes to answer the market, such as: incorporating "Auto-Aperture" with the M42, the light weight and compactness with the 'M' series, Aperture Priority overrides with the 'A' series, and Auto-Focus with the 'F' series. Modern Pentax lenses for digital SLR cameras have seen the elimination of the aperture ring completely as found on Pentax DA and D-FA series lenses. They use the Pentax KAF mount. All of these lenses have an autofocus feature, either operated from the camera body or from an internal SDM motor. Pentax compatible lenses are also made by third-party companies.
A pancake lens is a colloquial term for a flat, thin camera lens assembly. The majority are prime lenses of a normal or slightly wider angle of view, but some are zoom lenses.
A teleside converter is a secondary lens which is mounted on the front of a photographic lens to increase the effective focal length of the lens they are attached to. They are used on cameras and video cameras with non–interchangeable lenses to increase the magnification of the image. Their design is usually that of an afocal Galilean telescope that alters the width of the entering beam of light without affecting the divergence of the beam, so they can change the effective focal length 1 to 3 times without increasing focal ratio. The down side to teleside converters is they will vignette the image on the wide angle setting if used on a zoom lens. Minimum focal length without vignetting will increase inline with higher power of the teleside converter. Before vignetting appears, light fall-off will appear first and in general shooting this light fall-off may not be noticeable. The other concern is minimum working distance, so the teleside converter cannot be used below minimum working distance and it depends on both the camera and the teleside converter being used.
The Nikon F-mount teleconverters are a group of magnifying lenses mounted between the lens and camera bodies using the Nikon F-mount. Currently, 1.4x, 1.7x and 2x converters are available separately; a fourth, the 1.25x, is available only with Nikon's newest 800mm supertelephoto lens.
The Pentax Q series is a series of mirrorless interchangeable-lens cameras made by Pentax and introduced in 2011 with the initial model Pentax Q. As of September 2012, it was the world's smallest, lightest interchangeable lens digital camera. The first models used a 1/2.3" back-illuminated sensor CMOS image sensor. The Q7, introduced in June 2013, uses a larger 1/1.7" type sensor. The Q system is now discontinued.
The Pentax Q is a mirrorless interchangeable-lens camera introduced by Pentax on June 23, 2011.
The invention of the camera in the early 19th century led to an array of lens designs intended for photography. The problems of photographic lens design, creating a lens for a task that would cover a large, flat image plane, were well known even before the invention of photography due to the development of lenses to work with the focal plane of the camera obscura.
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