Lenses for SLR and DSLR cameras

Nikkor 28–200 mm zoom lens, extended to 200 mm at left and collapsed to 28 mm focal length at right

The focal length of a zoom lens is not fixed; instead it can be varied between a specified minimum and maximum value. Modern lens technology is such that the loss of image quality in zoom lenses (relative to non-zoom lenses) is minimal, and zoom lenses have become the standard lenses for SLRs and DSLRs. This is different from the late 1980s when, due to image quality concerns, most professional photographers still relied primarily on standard non-zoom lenses. However, zoom lenses still typically have a lower maximum aperture than fixed-focal ("prime") lenses for the same weight and cost, especially for shorter focal lengths.

Zoom lenses are often described by the ratio of their longest to shortest focal lengths. For example, a zoom lens with focal lengths ranging from 100 mm to 400 mm may be described as a 4:1 or "4×" zoom. Typical zoom lenses cover a 3.5× range, for example 24–90 mm (standard zoom) or 60–200 mm (telephoto zoom). "Super-zoom" lenses with a range of 10× or even 14× are becoming more common, although the image quality does typically suffer a bit compared with the more traditional zooms.

The maximum aperture for a zoom lens may be the same (constant) for all focal lengths, but it is more common that the maximum aperture is greater at the wide-angle end than at the telephoto end of the zoom range. For example, a 100 mm to 400 mm lens may have a maximum aperture of f/4.0 at the 100 mm end but will diminish to only f/5.6 at the 400 mm end of the zoom range. Zoom lenses with constant maximum apertures (such as f/2.8 for a 24–70mm lens) are usually reserved for lenses with higher build quality and are thus more expensive than those with variable maximum apertures.

Macro lenses are designed for extreme closeup work. Such lenses are popular for nature shooting such as small flowers, as well as for many technical applications. As most of these lenses can also focus to infinity and tend to be quite sharp, many are used as general-purpose optics.

Special-purpose perspective control lens for architectural photographs

Most users of SLR and DSLR cameras stick to using zoom lenses, while a few of the more adventurous amateurs and many professional photographers also invest in a few prime lenses. Special purpose lenses are, as the designation implies, for special purposes, and are not so common.

There are many different kinds of special purpose lenses, the most popular being fisheye lenses, which are extreme wide-angle lenses with an angle of view of up to 180 degrees or more, with very noticeable (sometimes intended) distortion. Perspective control lenses and soft-focus lenses, were more popular with film SLRs but are less popular for DSLRs because the same or similar results can be obtained with post-processing software.

The M42 lens mount has been used by Leica, Nikon, Pentax, Canon, Zenit, Praktica, Fujica, Cosina,

The M42 lens mount is a screw thread mounting standard for attaching lenses to 35 mm cameras, primarily single-lens reflex models. It is more accurately known as the M42 × 1 mm standard, which means that it is a metric screw thread of 42 mm diameter and 1 mm thread pitch. (The M42 lens mount should not be confused with the T-mount, which shares the 42mm throat diameter, but differs by having a 0.75mm thread pitch.) It was first used in Zeiss' Contax S of 1949; this East German branch of Zeiss also sold cameras under the Pentacon name; after merger with other East German photographic manufacturers, the name Praktica was used. M42 thread mount cameras first became well known under the Praktica brand, and thus the M42 mount is known as the Praktica thread mount.[1] Since there were no proprietary elements to the M42 mount, many other manufacturers used it; this has led to it being called the Universal thread mount or Universal screw mount by many. The M42 mount was also used by Pentax; thus, it is also known as the Pentax thread mount, despite the fact that Pentax did not originate it.

Also known as LTM (Leica Thread Mount). Used by Leica and Contax and several Leica copies, like the Soviet era FEDs, and others.

The electronic contacts (gold-plated) of an EF mount lens.

Canon introduced the EF-lens mount in 1987 as part of the EOS system. It broke with the most common technique for implementing autofocus at that time by not having a mechanical connection to a motor in the camera body, having instead only electrical connections and requiring a motor to be part of each autofocus lens.

The EF-S-mount is a newer subset of the EF standard, introduced in 2003. EF-S lenses can only be used on Canon digital cameras that use the APS-C sensor, for example the 400D (EOS Digital Rebel XTi) and the 40D. EF-S lenses can be distinguished by a white dot on the mount ring, as opposed to the red dot seen on standard EF lenses. Note that while an EF-S lens cannot be mounted on a camera that uses the EF mount, EF lenses can be mounted on cameras designed for the EF-S standard: for this reason, EF-S cameras carry both a red dot and a white dot on the mount.

As noted above under focal length, Canon makes DSLRs with various sensor sizes, and all using the EF or EF-S lens mounts. This leads to the interesting phenomenon of the same EF lens providing different angles of view depending on which camera it is mounted on.

Third-party lenses compatible with Canon's EF and EF-S mounts are manufactured by Sigma, Tamron, Tokina and Zeiss. The manufacturers of these lenses have reverse engineered the electronics of the EF lens mount. The use of these lenses is not supported by Canon. However, many users find these lenses to be cheaper (with the exception of Zeiss), and sometimes superior alternatives to Canon lenses.

The Four Thirds System was created by Olympus and Kodak in 2001, and is designed exclusively for digital cameras.[10] It is a semi-open standard that may be licensed by third parties. Currently Olympus, Leica (in cooperation with Panasonic), and Sigma are making lenses under Four Thirds System consortium licensing.

The Four Thirds System sensor size (17.3 mm x 13 mm) is the smallest currently being used in DSLR cameras. This leads to both advantages (theoretically smaller, lighter and cheaper lenses and camera bodies) and disadvantages (slightly lower image quality, especially in low-light situations).

There are currently over 35 lenses available for Four Thirds System cameras. A complete list can be found on Andrzej Wrotniak's web site.[11]

Micro Four Thirds is a variant on the standard Four Thirds system, developed by Olympus and Panasonic. While these cameras are technically not DSLRs, they are similar in operation, and use similar interchangeable lenses. The Micro Four Thirds lens mount is a slightly modified version of the standard Four Thirds mount, and a number of lenses have been built for it. Because the lack of a mirror, optical viewfinder, and a shorter flange-focal distance these lenses can be more compact than those for standard Four Thirds.

Standard Four Thirds lenses can be used on a Micro Four Thirds camera with full electronic communication using an adapter, but those that do not support contrast-detect autofocus will only autofocus slowly, if at all. Micro Four Thirds lenses can not be used on a standard Four Thirds camera.

A Minolta Maxxum AF 50mm f/1.7 prime lens with type “A” bayonet mount with the aperture all the way closed at F22.

The same Minolta AF 50mm f/1.7 prime lens with the aperture all the way open at F1.7.

Rear view of Minolta Maxxum/Dynax lens showing the port for the external autofocus drive

The Minolta A-mount system was introduced with the Minolta Maxxum 7000 camera in 1985, along with 11 AF-mount lenses.

In North America, Minolta began using the name 'Maxxum' for the SLR autofocus cameras, lenses and flashes while in Europe they were called 'AF' (first series) and 'Dynax' (second and later generations), and in Asia the 'α' (Alpha) branding was used, though they were otherwise identical in appearance and function - all of the equipment is 100% interchangeable regardless which of the names it carries.

Most Minolta A-mount compatible lenses, whether built by Minolta or one of the aftermarket lens manufacturers, are focused externally by a shaft connecting the autofocus computer and motor inside the camera body that mechanically connects to the internal focusing gears inside of the lens body. A couple of later Minolta lenses do have a built-in ultrasonic focus motor (SSM lenses), like other SLR and DSLR systems (i.e. Canon and Nikon), where the AF computer is inside the camera body and there is a digital interface connecting body to an electric motor and the focusing gears built into the lens body.

This shaft driven autofocus design has several benefits such as allowing for smaller and lighter lenses and also keeps the cost of lenses down because there are no internal focusing motors or digital interfaces built into the lens. Keeping the autofocus motors inside the camera body and as far away from the lens glass as possible, reduces vibration, an additional benefit. This highly reliable shaft-driven autofocus system was extremely successful but is not seen in modern lenses.

Minolta (and later Konica Minolta) followed up by producing a large number of AF-mount lenses over the years up until 2004. Konica Minolta sold the rights to their Minolta AF lens mount to Sony in 2006.

Sony acquired Konica Minolta's camera technologies in 2006, and chose the "α" brand name, already in use by Minolta in Asia, for their new "Sony α" digital SLR system. The company has since abandoned traditional SLR design, and now uses the "α" brand name for its current line of SLT and ILCA cameras with fixed semi-reflective mirrors and electronic viewfinders, as well as its current line of E-mount mirrorless cameras.

The Minolta A-mount was retained from the old cameras and was originally named the "Sony α mount system".[12]

Sony has produced several new lenses for its A-mount, and the current list of Minolta and Sony A-mount lenses has over 60 entries.

Some of the newest A-mount lenses are designated "DT" for Digital Technology; these are for digital cameras with APS-C sensors, and will result in vignetting if used on a film SLR or a full frame DSLR or full frame SLT camera.

Third-party lenses for the AF lens mount are made by Zeiss, Sigma, Tamron, Tokina and Vivitar.

The Nikon F-mount was introduced by Nikon in 1959, and is thus one of the most venerable lens mounts still in existence. Another factor that makes the Nikon F-mount popular is that several other camera manufacturers, for example Fujifilm, have adopted it. F-mount photographic lenses are currently made by Nikon, Zeiss, Voigtländer, Schneider, Sigma, Tokina, Tamron, Hartblei, Kiev-Arsenal, Lensbaby, Vivitar, and others, and over 400 lenses are compatible with the system.

Most Nikon F-mount lenses cover the standard 36×24 mm area of 135 film, while "DX" designated lenses cover the 24×16 mm area of the Nikon DX format DSLR sensors, commonly referred to as APS-C format. While "DX" lenses can be physically mounted on any Nikon film or digital SLR that support the "AI" exposure indexing feature (produced from 1977), there will be some degree of vignetting when used on film cameras, depending on zoom setting. All Nikon full-frame "FX" DSLRs have a DX-compatible mode that, by default when a DX-format lens is attached, crops the captured frames to the DX format and adjusts the viewfinder to reflect the smaller capture area. This can be overridden by the user if desired.

There are basically three types of F mount Nikon lens:

1. MF = Manual focus lenses
2. AF & AF-D = Auto focus by camera body driven focus motor, the D version provides distance information
3. AF-I & AF-S = Auto focus by integrated/ultrasonic motor in lens; see also List of Nikon F-mount lenses with integrated autofocus motors

Industrial F-mount lenses have varying, often small, film/sensor coverage. Older F-mount lenses designed for film cameras will work on modern SLR or DSLR cameras with some limitations, typically not providing autofocus or automatic aperture setting. Entry level Nikon DSLRs such as Nikon D40, D40X, D60, D3000, D3100, D5000 and D5100 do not have an integrated focus motor, so they will not autofocus with AF & AF-D lenses. Similarly, some AF-I & AF-S lenses will not work on some older Nikon AF film SLRs.

Nikon D200 digital SLR

The Nikon 1-mount was announced on 21 September 2011 together with the Nikon 1 series high-speed mirrorless interchangeable-lens cameras.

Pentax K10D "Crippled" K_AF2 mount

The Pentax K-mount (or just "PK mount") was created by Pentax in 1975, and has been used by all Pentax 35 mm and digital SLRs since. The mount has been developed over the years, resulting in a large number of designations such as K_F mount, K_A mount, K_AF mount, K_AF2 mount and K_A2 mount, plus a couple of more recent versions that are not completely backward-compatible and are thus referred to as "crippled" versions. ("Crippled" in this context does not imply any lack of modern functionality, just a lack of compatibility with past lenses.) For more information see the Pentax K mount article or Bojidar Dimitrov's web site.[13]

A number of other manufacturers have produced K-mount lenses, and several other manufacturers (such as Konica and Ricoh) have made K-mount cameras. In 2005 Pentax and Samsung entered into a cooperation resulting in the Samsung GX line of DSLRs, based largely on Pentax technology including the Pentax K mount.

Sigma Corporation, better known for manufacturing lenses for other cameras, has made some film SLR and DSLR cameras themselves. These cameras use the Sigma SA-mount, for which Sigma makes a line of lenses.

The Sigma DSLR cameras that use the SA mount are the Sigma SD9, SD10, SD14, SD15 and SD1 Merrill. These cameras are noteworthy for their use of the Foveon X3 sensor, an image sensor that works on quite different principles from the sensors used in all other digital cameras.

The Nikon F-mount lens systems and the Pentax K-mount systems are the only 35 mm SLR camera systems (apart from the Leica M-mount rangefinder system) that allow a photographer to use a mechanical SLR camera body, a fully automatic SLR camera body, and a DSLR camera body, all utilizing the same lenses. The only aspects of these manufacturers' lenses that have changed are the addition of electronic contacts, autofocus abilities and, in some cases, the elimination of the external aperture ring for electronic control (i.e., Nikon's 'G-type' auto-Nikkors, which cannot be used on a mechanical SLR camera body).

Canon, Minolta (Sony), Olympus, and other manufacturers have changed lens mounts. Much older Canon film cameras used the FD lens mount, which was discontinued in 1987 in favor of the EF lens mount. Olympus discontinued the OM lens mount for the OM series cameras in favor of the Four Thirds System lens mount. However, due to the size of the Four Thirds mount it is possible to fit legacy SLR lenses from any manufacturer using an adapter, albeit with manual aperture and focus control. Minolta (Sony after 2006) phased out its bayonet-mount MC and MD Rokkor lenses for a modified bayonet mount (supporting autofocus) in 1985. All Minolta A-mount lenses work on compatible Minolta SLR film bodies and on Sony A-mount DSLR and SLT bodies.