Canon EF 50mm lens
The EF 50mm lenses are a group of normal prime lenses made by Canon that share the same focal length. These lenses are based on the classic double-Gauss lens, with the f/1.8 being a standard six-element double-Gauss with an air gap and powers between element 2 and 3 and its faster cousins adding additional elements. The 50mm focal length, when used with a 35mm film or full-frame sensor, has been widely considered to match the perspective seen by the human eye.
Canon 50mm lenses have an EF type mount that fits the Canon EOS line of cameras. When pairing a 50mm lens to a Canon DSLR with an APS-C sized sensor, the crop factor effectively turns the 50mm focal length into a 80mm field of view.
Six EF 50mm lenses have been sold by Canon:
- f/1.0L USM (discontinued, replaced by f/1.2L USM)
- f/1.2L USM
- f/1.4 USM
- f/1.8 (discontinued, replaced by f/1.8 II)
- f/1.8 II
- f/2.5 Compact Macro
EF 50mm f/1.0L USM 
The discontinued EF 50mm f/1.0L USM is a professional L series autofocus lens. On the used market sells for as much as double the original retail value. It was the fastest SLR lens in production during its lifetime. This lens has a metal body and mount, and plastic extremities. It also features a wide rubber focus ring that is damped, a distance window with infrared index, and the ability to set the focus range from 0.6m to infinity, or 1m to infinity. In common with the EF 85mm f/1.2L USM it uses an electronic "focus by wire" system and requires power from the camera in order to manual focus. The 8-blade diaphragm and maximum aperture of f/1.0 give this lens the ability to create extremely shallow depth of field effects and to support low light situations. The optical construction of this lens contains 11 lens elements, including two ground and polished aspherical lens elements. This lens uses a floating front extension focusing system, powered by a ring-type USM motor. The front of the lens does not rotate, but does extend when focusing.
Despite its price and large maximum aperture, the 1.0L was not a particularly sharp lens at any aperture, and the two cheaper 50mm options offered far better sharpness when stopped down beyond about f/2.8. This, combined with the high production cost and low sales volume, led to it being discontinued in 2000 and eventually superseded by the f/1.2 edition.
EF 50mm f/1.2L USM 
The EF 50mm f/1.2L USM is a professional L series lens designed to replace the EF 50mm f/1.0L USM. It is constructed with a metal body and mount, and plastic extremities. This lens features a wide rubber focusing ring that is damped, a distance window with infrared index, and is weather-sealed. A circular, 8-blade diaphragm and maximum aperture of f/1.2 give this lens the ability to create very shallow depth of field effects with smooth background blur. The optical construction of this lens contains 8 lens elements, including one ground and polished aspherical lens element. This lens uses a floating front extension focusing system, powered by a ring-type USM motor. The front of the lens does not rotate or extend when focusing.
EF 50mm f/1.4 USM 
The EF 50mm f/1.4 USM is a consumer- and professional-level lens. It is the least expensive f/1.4 aperture lens that Canon currently manufactures. It is constructed with a plastic body and a metal mount. This lens features a distance window with infrared index. An 8-blade diaphragm and maximum aperture of f/1.4 give this lens the ability to create shallow depth of field effects. The optical construction of this lens contains 7 lens elements including 2 high refraction elements, but no aspherical, high dispersion or calcium fluoride elements. The lens uses a front extension focusing system, powered by a micro USM motor. Even though this lens uses a micro USM motor, it still has FTM (full-time manual focus) available. Auto-focus speed of this lens is fast, but not as quick as most ring-USM-based lenses. The front of the lens does not rotate, but extend up to about one centimeter when focusing.
EF 50mm f/1.8 
The EF 50mm f/1.8 is an economy level lens (discontinued in 1990), which has been replaced by the EF 50mm f/1.8 II. The body is plastic but the lens mount is metal, and it features a distance window with infrared index. A 5 blade maximum aperture of f/1.8 gives this lens the ability to create depth of field effects.
The optical construction of this lens contains 6 lens elements, with no special elements. This lens uses a front extension focusing system, powered by an AFD motor. The front of the lens does not rotate when focusing, making it compatible with circular polarisers.
Auto-focus speed, despite the AFD motor, is moderately fast but audible.
EF 50mm f/1.8 II 
The EF 50mm f/1.8 II replaced the EF 50mm f/1.8 in 1991. The original (now discontinued) Canon EF 50mm f/1.8 lens came equipped with a metal lens mount, distance scale, IR focusing label and separate manual focusing ring. The current Canon EF 50mm f/1.8 II lens has a plastic lens mount and is missing a distance scale, IR focusing label and dedicated manual focusing ring. Instead the manual focusing ring has been replaced by a very small thin focusing ring on the front tip of the lens. However the lens does not suffer from rotating front lens element and can be used with polarizing filters. The optics for both lenses are identical, with 6 elements in 5 groups and a 5 blade diaphragm. This lens has a 52mm filter thread.
Because of its low price and sharp optical quality, this lens has earned the nicknames 'nifty fifty' and 'plastic fantastic'. When shooting at f/1.8, it offers a very shallow depth of field which is beneficial for isolating subjects against a blurred background (bokeh).
EF 50mm f/2.5 Compact Macro 
The EF 50mm f/2.5 Compact Macro is a relatively inexpensive macro lens with a minimum focusing distance of 23cm (9 inches) offering a maximum magnification of 0.5x actual size. Reviewers describe the lens as having "decent"/"mid-level" build quality, with very good color and contrast, "absolutely negligible" distortion, very sharp after f/4 and peak performance at f/5.6. However, auto-focusing is relatively slow and noisy.
The maximum 0.5x magnification means this lens is more suitable for photographing documents, products and objects at least 5cm (2 inches) wide than small insects etc. The outer barrel is grooved to accept Canon's MR-14 ring flash which can be used as the principal light source for close-ups or as on-axis fill lighting for portraits. The six-blade diaphragm provides reasonably good out-of-focus blur (bokeh) for portrait work.
First introduced in 1987, the lens is constructed with a plastic body and metal mount, and features a distance window with infrared index and magnification markings. The optional Life-Size Converter EF adapts the lens to produce a maximum magnification of 1:1. Attaching the converter increases the lens focal length to 70mm, reduces the maximum aperture to f/3.5 and limits the focal range. Magnification markings for the converter are shown on the (extending) inner lens barrel.
Specifications of the EF 50mm lenses 
|Attribute||f/1.0L USM||f/1.2L USM||f/1.4 USM||f/1.8||f/1.8 II||f/2.5 Compact Macro|
|Construction||9 groups / 11 elements||6 groups / 8 elements||6 groups / 7 elements||5 groups / 6 elements||8 groups / 9 elements|
|# of diaphragm blades||8||5||6|
|Closest focusing distance||2ft / 0.6m||1.5ft / 0.45m||0.749ft / 0.228m|
|Max. magnification||0.11x||0.15x (1:6.6)||0.50x (1:2)|
|Horizontal viewing angle||40°|
|Diagonal viewing angle||46°|
|Vertical viewing angle||27°|
|Weight||2.2lb / 985g||1.2lb / 545g||0.6lb / 290g||0.4lb / 190g||0.3lb / 130g||0.6lb / 280g|
|Maximum diameter||3.6in / 91.5mm||3.6in / 85.8mm||2.9in / 73.8mm||2.6in / 67.4mm||2.6in / 68.2mm||2.7in / 67.6mm|
|Length||3.2in / 81.5mm||2.6in / 65.5mm||2.0in / 50.5mm||1.7in / 42.5mm||1.6in / 41mm||2.5in / 63mm|
|Release date||September 1989||August 2006||June 1993||March 1987||December 1990||December 1987|
|Currently in production?||No||Yes||No||Yes|
|Street Price $||$1500 to $5000||$1599||$450||$150-$200||$140||$230|
- 50mm and the Human Eye, Gary Voth. Retrieved 2011-01-10.
- Canon Inc.. "EF 50mm f/1.0L USM". Canon Camera Museum. Retrieved 2007-08-06.
- Canon Inc.. "EF 50mm f/1.2L USM". Canon Camera Museum. Retrieved 2007-08-06.
- Canon Inc.. "EF 50mm f/1.4 USM". Canon Camera Museum. Retrieved 2007-08-06.
- Canon Inc.. "EF 50mm f/1.8 II". Canon Camera Museum. Retrieved 2007-08-06.
- Canon Inc.. "EF 50mm f/2.5 Compact Macro". Canon Camera Museum. Retrieved 2010-08-09.
- "Canon EF 50mm f/2.5 macro - Review / Test Report - Analysis". Photozone. Retrieved 2010-06-18.
- "Canon EF 50mm f/2.5 Macro Lens Review". The-Digital-Picture.com. Retrieved 2010-06-18.
- Canon Inc.. "Life-Size Converter EF". Canon USA. Retrieved 2007-10-15.
- Price based on 2009 price survey[by whom?]. Price varies significantly by lens condition and perceived availability.
50mm f/1.0L USM 
50mm f/1.2L USM 
50mm f/1.4 USM 
50mm f/1.8 I & II 
- Comparison between Mark I & II
- The-Digital-Picture (includes comparison of 50mm lenses)
50mm f/2.5 Compact Macro 
- Comparison of 50mm f/1.4 and 50mm f/1.8 at photo.net
- Comparison of 50mm f/1.2L and 50mm f/1.4 by Valentin Blank