Lens speed

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A fast prime (fixed focal length) lens, the Canon 50mm f/1.4 (left), and a slower zoom lens, the Canon 18-55mm f/3.5-5.6 (right); this lens is faster at 18mm than it is at 55mm. Lensspeed.jpg
A fast prime (fixed focal length) lens, the Canon 50mm f/1.4 (left), and a slower zoom lens, the Canon 18–55mm f/3.5–5.6 (right); this lens is faster at 18mm than it is at 55mm.

Lens speed refers to the maximum aperture diameter, or minimum f-number, of a photographic lens. A lens with a larger maximum aperture (that is, a smaller minimum f-number) is called a "fast lens" because it can achieve the same exposure with a faster shutter speed. Conversely, a smaller maximum aperture (larger minimum f-number) is "slow" because it delivers less light intensity and requires a slower (longer) shutter speed.

Contents

A fast lens speed is desirable in taking pictures in dim light, or with long telephoto lenses and for controlling depth of field and bokeh, especially in portrait photography, [1] and for sports photography and photojournalism.

Lenses may also be referred to as being "faster" or "slower" than one another; so an f/3.5 lens can be described as faster than an f/5.6.

Tradeoffs

Attaining maximum lens speed requires engineering tradeoffs, and as such, "prime" (fixed focal length) lenses are generally faster than zoom lenses. [2]

With 35mm film cameras and full-frame digital cameras, the fastest lenses are typically in the "normal lens" range near 50mm and there are several high-quality fast lenses available that are relatively inexpensive. For example, the Canon EF 50mm f/1.8 II or Nikon AF Nikkor 50mm f/1.8D are very inexpensive, but quite fast and optically well-regarded. Old fast manual focus lenses, just as the Nikkor-S(C) or Nikkor AI-S 50mm f/1.4, were historically produced abundantly, and are thus sold relatively inexpensively on the used lens market.

Especially outside of the "normal lenses", lens speed also tends to correlate with the price and/or quality of the lens. This is because lenses with larger maximum apertures require greater care with regard to design, precision of manufacture, special coatings and quality of glass. At wide apertures, spherical aberration becomes more significant and must be corrected. Faster telephoto and wide-angle retrofocus designs tend to be much more expensive.

A telecompressor, also known as a speed booster, may be used to increase the speed of a lens with a corresponding reduction to its focal length. For example, the Metabones 0.58x BMPCC speed booster may be combined with a f/1.2 lens to produce f/0.74. [3]

Fast lenses

The fastest lenses in general production now are f/1.2 or f/1.4, with more at f/1.8 and f/2.0, and many at f/2.8 or slower. What is considered "fast" has evolved to lower f-numbers over the years, due to advances in lens design, optical manufacturing, quality of glass, optical coatings, and the move toward smaller imaging formats. For example, the 1911 Encyclopædia Britannica states that "...[Lenses] are also sometimes classified according to their rapidity, as expressed by their effective apertures, into extra rapid, with apertures larger than f/6; rapid, with apertures from f/6 to f/8; slow, with apertures less than f/11."

Canon 85mm f/1.8 and f/1.2 showing their large entrance pupils Canon 85mm comparison (front).jpg
Canon 85mm f/1.8 and f/1.2 showing their large entrance pupils

For scale, note that f/0.5, f/0.7, f/1.0, f/1.4, and f/2.0 are each 1 f-stop apart (2× as fast), as an f-stop corresponds to a factor of square root of 2, about 1.4. Thus around f/1.0, a change of 0.1 corresponds to about 1/4 of an f-stop (by linear approximation): f/1.0 is about 50% faster than f/1.2, which is about 50% faster than f/1.4.

As of 2017, Canon, Nikon, Pentax and Sony all make an autofocus 50mm f/1.4 lens. These are not unusual lenses and are relatively inexpensive. Canon also makes autofocus 50mm and 85mm f/1.2 lenses, while Nikon makes a manual focus 58mm f/0.95 lens and an autofocus 85mm f/1.4; see Canon EF 50mm lenses and Canon EF 85mm lenses for details. Pentax makes a 50mm f/1.4 lens and 55mm f/1.4 lens for APS-C cameras; see Pentax lenses. Sony makes a 50mm f/1.4 lens which is a continuation of the Minolta AF 50mm f/1.4 lens, and two lenses with Carl Zeiss: a 50mm f/1.4 and 85mm f/1.4.

The maximum exposure time in free-hand photography can be enhanced even more also for fast lenses, if the camera is equipped with an image stabilisation system. In 2014 Panasonic introduced the fastest lens with in-built stabilisation, the Leica Nocticron 42.5 mm f/1.2, which in the meantime even can be operated with dual image stabilisation (Dual I.S.), provided that the camera body has an additional stabilising system at the image sensor, too.

In the mid 60s there was something of a fad for fast lenses among the major manufacturers. [4] In 1966 in response to the trend Carl Zeiss displayed a prop lens christened the Super-Q-Gigantar 40mm f/0.33 at photokina. [4] Made from various parts found around the factory (the lenses came from a darkroom condenser enlarger), the claimed speed and focal lengths were purely nominal and it wasn't usable for photography. [4] [5]

Maximum possible speed

Theoretically, the smallest f-number is 0 (or numerical aperture of 1), corresponding to a lens with an infinite exit pupil diameter. In practice that cannot be reached due to mechanical constraints of the camera system (shutter or mirror clearance, mount diameter). Even for systems that can be designed without significant constraints on lens size and image plane distance (e.g. microscopy and photolithography systems), the cost of going beyond a numerical aperture of 0.95 (f/0.164) is usually prohibitive.

In SLR camera systems, typical mount diameters are in the range of 44-54 mm, with flange distances around 45 mm. This limits the maximum possible f number to f/1.0 to f/1.2, with rather strong vignetting towards the edges of the image. Flange distances are significantly smaller for rangefinder and mirrorless cameras (even below 20 mm), theoretically enabling designs down to something like f/0.7 or even faster. The chance of seeing these in practice will be slim, since their practical use is limited, and the cost and weight are likely not competitive with respect to equivalent imaging solutions employing larger sensors.

List of ultrafast lenses

Some of the fastest camera lenses in production as of 2017 were as follows:

The following camera lenses are no longer in production as of 2010:

Many very fast lenses exist in C-mount (such as used by 16mm film cameras, CCTV, medical & scientific imaging systems), including:

Very fast lenses in D-mount for 8mm movie use on H8 cameras:

Very fast lenses used in x-ray machines:

Related Research Articles

Aperture Hole or opening through which light travels

In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.

Rangefinder camera

A rangefinder camera is a camera fitted with a rangefinder, typically a split-image rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most varieties of rangefinder show two images of the same subject, one of which moves when a calibrated wheel is turned; when the two images coincide and fuse into one, the distance can be read off the wheel. Older, non-coupled rangefinder cameras display the focusing distance and require the photographer to transfer the value to the lens focus ring; cameras without built-in rangefinders could have an external rangefinder fitted into the accessory shoe. Earlier cameras of this type had separate viewfinder and rangefinder windows; later the rangefinder was incorporated into the viewfinder. More modern designs have rangefinders coupled to the focusing mechanism so that the lens is focused correctly when the rangefinder images fuse; compare with the focusing screen in non-autofocus SLRs.

Carl Zeiss AG German optics company

Carl Zeiss AG, branded as ZEISS, is a German manufacturer of optical systems and optoelectronics, founded in Jena, Germany in 1846 by optician Carl Zeiss. Together with Ernst Abbe and Otto Schott he laid the foundation for today's multi-national company. The current company emerged from a reunification of Carl Zeiss companies in East and West Germany with a consolidation phase in the 1990s. ZEISS is active in four business segments with approximately equal revenue, Industrial Quality and Research, Medical Technology, Consumer Markets and Semiconductor Manufacturing Technology in almost 50 countries, has 30 production sites and around 25 development sites worldwide.

Cosina Japanese optical glass manufacturer

Cosina Co., Ltd. is a manufacturer of high-end optical glass, optical precision equipment, cameras, video and electronic related equipment, based in Nakano, Nagano Prefecture, Japan.

Nikon F-mount Lens mount

The Nikon F-mount is a type of interchangeable lens mount developed by Nikon for its 35mm format single-lens reflex cameras. The F-mount was first introduced on the Nikon F camera in 1958, and features a three-lug bayonet mount with a 44 mm throat and a flange to focal plane distance of 46.5 mm. The company continues, with the 2020 D6 model, to use variations of the same lens mount specification for its film and digital SLR cameras.

Pentax K-mount Series of camera lens mounts made by Pentax

The Pentax K-mount, sometimes referred to as the "PK-mount", is a bayonet lens mount standard for mounting interchangeable photographic lenses to 35 mm single-lens reflex (SLR) cameras. It was created by Pentax in 1975, and has since been used by all Pentax 35 mm and digital SLRs and also the MILC Pentax K-01. A number of other manufacturers have also produced many K-mount lenses and K-mount cameras.

Double-Gauss lens

The double Gauss lens is a compound lens used mostly in camera lenses that reduces optical aberrations over a large focal plane.

Nikon FM10

The Nikon FM10 is a manual focus 35 mm film camera sold by Nikon Corporation. It is of SLR design and was first available in 1995. It is normally sold in a kit that includes a Zoom Nikkor 35–70 mm f/3.5-4.8 zoom lens, although a Zoom Nikkor 70–210 mm f/4.5-5.6 zoom lens is also available. An electronic companion model known as the FE10 was also sold at one stage.

Leica M mount

The Leica M mount is a camera lens mount introduced in 1954 with the Leica M3, and a range of lenses. It has been used on all the Leica M-series cameras and certain accessories up to the current film Leica M-A and digital Leica M10 cameras.

Cosina Voigtländer refers to photographic products manufactured by Cosina under the Voigtländer name since 1999. Cosina leases rights to the Voigtländer name from RINGFOTO GmbH & Co. ALFO Marketing KG in Germany. Cosina Voigtländer products have included 35mm film SLR and rangefinder camera bodies, and lenses for the M39 lens mount, M42 lens mount, Leica M mount, and other lens mounts.

35 mm Bessa

The Bessa family of cameras is manufactured in Japan by Cosina as a revival of the Voigtländer brand name.

The Jupiter series of lenses are Russian camera lenses made by various manufacturers in the former Soviet Union. They were made to fit many camera types of the time, from pre-WWII rangefinders to almost modern SLRs. They are copied from Zeiss pre-WWII designs with incremental improvements, such as coatings, introduced during production. The majority of them are based on Zeiss Sonnar optical scheme, but that's not a rule.

Nikon S-mount 35mm lens mount

The Nikon S-mount is a type of interchangeable lens mount used by a series of Nikon 35mm rangefinder cameras. The lenses were sold under the name Nikkor.

Panasonic Lumix DMC-GH2

The Panasonic Lumix DMC-GH2 is a digital camera with HD video recording capability that is part of the Micro Four Thirds system. Though commonly referred to as a DSLR camera, it has no mirror or optical viewfinder, but has instead both a fold-out LCD screen and a electronic viewfinder.

Fujifilm X-mount

The Fujifilm X-mount is a type of interchangeable lens mount designed by Fujifilm for use in those cameras in their X-series line that have interchangeable-lenses. These lenses are designed for 23.6mm x 15.6mm APS-C sensors.

History of photographic lens design

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.

Nikon Z-mount Digital camera lens mount

Nikon Z-mount is an interchangeable lens mount developed by Nikon for its full-frame mirrorless digital cameras. In late 2018, Nikon released two cameras that use this mount, the Nikon Z 7 and the Nikon Z 6. In late 2019, Nikon announced their first APS-C sensor size Z-mount camera, the Nikon Z 50. In October 2020, Nikon announced the Nikon Z 6II and Nikon Z 7II, which succeed the Z 6 and Z 7, respectively.

Hologon

The Zeiss Hologon is an ultra wide-angle f=15mm f/8 triplet lens, providing a 110° angle of view for 35mm format cameras. The Hologon was originally fitted to a dedicated camera, the Zeiss Ikon Contarex Hologon in the late 1960s; as sales of that camera were poor and the Zeiss Ikon company itself was going bankrupt, an additional 225 lenses were made in Leica M mount and released for sale in 1972 as the only Zeiss-branded lenses for Leica rangefinders until the ZM line was released in 2005. The Hologon name was revived in 1994 for a recomputed f=16mm f/8 lens fitted to the Contax G series of rangefinder cameras.

Summarit

The name Summarit is used by Leica to designate camera lenses that have a maximum aperture of f/2.4. The name has been in used since 1949.

References

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  12. "NOKTOR – Ultra Fast Lenses". Archived from the original on 2010-02-03. Retrieved 2010-05-26.
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  14. "USAF Lens Datasheets - Type 1 Aerial Reconnaissance". archive.org. Retrieved 4 October 2013.
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