click on the sentence to go to the relevant chapter
A lens is a piece of glass or synthetic material used to catch transmitted light on a film or sensor plane. One or more lenses are used in a construction, known as objective. Not all sorts of glass can be used for telescopes, microscopes, binoculars or photographic equipment. Since Nikon Corporation started in 1917 as a merger of - among others the glassworks of Fujii Bros.- it is able to melt its own glass. Today Nikon may choose out of nearly 300 ´recipes´ to form the sort or type of glass, needed to produce a specific lens.
Nikon Corporation sent off an application for the trademark ´Nikkor´ in 1931, which was approved in April 1932. Since then all photographic lenses are called Nikkor. Some of them with a prefix or with a suffix, indicating the (special) purpose of the lens or one or more of its characteristics.
The very first lenses - for Nikon rangefinder cameras - were engraved with the (former) company´s name ´Nippon Kogaku Tokyo´ or ´Nippon Kogaku Japan´. During the American occupation of Japan - just after W.W.II - all lenses had an additional engraving: ´made in occupied japan´ and those that were sold in military shops were ´EP´ engraved. Early RF lenses made for Contax cameras have a ´C´ engraved on the side of the lens barrel. The ´C´ on the lens ring of all lenses indicates ´coating´.
Prefixes like W (Wide), AF (autofocus), R-UW (Underwater), Fisheye, Bellows, UV-Micro, Zoom, VR (vibration reduction) are a few of them. Suffixes after the name ´Nikkor´ are indicating the number of elements in the lens. These suffixes were used up to the early 1970´s.
U = (Uns) for 1 element, B = (Bini) for 2 elements, T = (Tres) for 3 elements; Q = (Quattor) for 4 elements; P = (Pente) for 5 elements; H = (Hex) for 6 elements; S = (Septem) for 7 elements; O = (Octo) for 8 elements; N = (Novem) for 9 elements and D = (Decem) for 10 elements.
Nearly all lenses had in their name ring ´auto´ engraved, referring to the automatic diaphragm.
Most modern lenses have - on the side of the lens barrel - an engraving telling us the country it is made in: made in japan - lens made in japan - made in thailand, etc. Some lenses sold in the United States of America have ´US´ engraved before its serial number.
Nikon Corporation has given nearly all its products a serial number. Among collectors it has become famous for its enigmatic numbering system. If one think that there is a logic in this system, just forget it! Most lenses are numbered with a 6-digit number, sometimes reflecting or referring to its technical specification. Mis-numberings and/or mis-engravings are very rare. It is a pity that modern lenses aren´t engraved anymore, but have a simple sticker with a number on it. Those stickers can be removed or changed. Serious collectors have to be careful with collecting numbers as many name rings can be changed. Most name rings are locked by a tiny set screw on the side of the ring or lens barrel. If that screw is damaged by a screwdriver it might be exchanged.
All Nikon lenses, used in photographic lenses or binoculars are coated to illuminate internal reflections and to improve light transmission. A non-coated photographic lens will reflect 4 - 7 % of all entering light, a single coated lens can reflect 2 % and a multi coated lens less than 0.5 %. A non-coated photographic lens with e.g. 6 elements in 5 groups has 10 glass-to-air surfaces and will loose up to 41 % because of internal reflection! In the early years of photography it was therefore impossible to produce lenses of more than 4 or 5 elements as internal reflection ruined any image. The German lens maker Carl Zeiss invented around 1935 a method of lens coating (vacuum-vapoured) that was adopted and used by Nikon in the late 1930´s. After W.W. II most lens makers made use of multiple coatings (up to 8 layers) on all glass-to-air surfaces, reducing reflection to 2 %, which - nowadays - is still unacceptable. Nikon improved its coatings in 1967. The first lenses benefited from that modern multiple layer coating were the Nikkor-S 1.2/55mm. and Nikkor 1.4/35mm. Later coatings (Nikon Integrated Coating, Super Integrated Coating and Nano-cristal Coating) have made Nikkor lenses famous in the world of photography.
The world´s largest optical glass maker Hoya (Japan) and the German lens maker Schneider once tested several old and new lenses. The fast and famous Nikkor-N 1.1-5 cm. for the Nikon rangefinder cameras has 12 air-to-glass surfaces which - together - are reflecting an amount of light resulting in an effective aperture - at full opening - of f/1.24. It´s obvious that this lens would perform even better if coated using the latest technology.
Light in fact is an electro-magnetic wave of a certain wavelength with a speed of approx. 300,000 kilometer per second! Human eyes can detect light with a wavelength of 400 - 760 nm. (nanometer). Colors like indigo start at 400 nm, followed by blue at 505 nm., green at 560 nm., etc. up to deep red at 760 nm. At a shorter wavelength as 400 nm ultraviolet A, B and C and, even shorter, various X-rays can be detected (but not by human eye). Above 760 nm. infrared can be found. Detecting a color is a matter of reflection and absorption. Is white light reflected by an item we will see that item as being black. An item reflects the color we see and absorbs all other colors. So if light travels through a lens of a binocular, so called interference-reflection will occur, resulting in loss in light. If that lens is coated, absorbing reflection, the light transmission will not decrease. Research has shown that if a coating is 1/4 of the thickness of the wavelength of a particular color and if the breaking index of the coating substance equals the root of the breaking index of the glass in use, maximum absorption of that color will be the result. If we take e.g. the color green at 560 nm. the coating should be 140 nm. thick. The more coatings will be used the better light transmission will be gained. Nowadays reflections of 0.3 % or less are normal.
Nikkor lens forks
From the very first lens, made for the Nikon single lens reflex cameras, Nikon fitted nearly all lenses with a fork (aka prong) to couple the aperture mechanism in the lens with the exposure meter in the camera (or Photomic view finder). The first version of the fork has a triangular shape. To improve mounting a lens to the camera body the second version has a rounded top. After the introduction of the Automatic Indexing (AI) system in 1977 all Nikkor lenses were fitted with a open fork to make the aperture data on the aperture ring of a lens readable which is projected via a little mirror in front of the prism into the view finder. Later the forks were reshaped with larger openings to improve readability. Modern AF-lenses are not longer equipped with a fork, although some have little markings on the ridge where forks can be placed if needed. If you need a fork contact your local Nikon dealer or the Nikon Professional Service desk.
From left: triangular fork, rounded fork, AI-fork, larger AI-fork
Some older forks were lowered on one side to ease mounting the lens
Nikon cameras have a special mount to accommodate a lens. The Nikon rangefinder lenses have the so called S-mount, more or less copied from the early Contax rangefinder cameras.
Nikon S-mount with ´springy´ locking tab in top (near O of Nikon)
The Nikon SLR´s (for film, sensor or APS) have since they appeared on the market in 1959 the so called F-mount, called after the famous Nikon engineer Fuketa.
Nikon F-mount on Nikon´s first SLR camera - modern mounts have electronic contacts and AF drive shaft
The Nikonos underwater cameras have their own mount. Via adapters most Nikkor lenses are interchangeable. The Nikonos cameras and lenses - however - are specifically designed and will not fit on any other camera.
If whatever lens should be placed on a camera the lens mount is important. But there is another element playing an important role: the register (or flange distance) of a camera. The register of a camera is the distance between the lens mount and the film or sensor plane. The back focal distance is the distance from the back of a lens to the film/sensor plane , which is different.
Nikon rangefinder cameras have a register of 34.85 mm., all Nikon SLR´s (film, digital and APS) have a register of 46.5 mm. In principle any Nikkor SLR-lens would fit a Nikon rangefinder camera; the other way round is possible as well but the lens can´t be focused at/to infinity. All Nikkor lenses with the S-mount and the F-mount are designed and manufactured to fit both respective cameras. Nikon has produced adapters to fit a SLR-lens on a rangefinder camera and vice versa. There are also adapters to fit a Leica thread (= 39 mm.) lens on a Nikon camera.
Cameras of other brands could make use of Nikkor lenses, as long as their register is shorter than that of the Nikon SLR. Canon SLR´s have a register of 44 mm, Contax SLR´s have 45.5 mm and Leica screw mount cameras have a register of 28.8 mm. In principle these cameras could be fitted with a Nikkor lens. For some of the cameras mentioned special adapters are made (NOT by Nikon!). Certain lens manufacturers, like Sigma, Tokina, Tamron and many others are producing special (permanent or detachable) mounts so their lenses will fit on various SLR´s. Older lenses of various brands were fitted with a 42 mm. thread mount. In fact there are two different mounts: the M-42 and the so called T-2 mount. The M-42 has a thread of 42 mm. with a pitch of 1 mm., while the T-2 thread mount has a thread of 42 mm. but a pitch of 0.75 mm. Also their registers are different: M-42 = 45.46 mm., the T-2 = 55 mm.
Many movie makers and filmers made/make use of Nikkor lenses. It is possible to fit a Nikkor lens via a special adapter to a C-mount movie camera, bearing in mind that the register of any C-mount movie camera is 17.526 mm.
Aperture
Aperture (from Latin apertura = open) is an indication of the maximum opening of a lens; or in other words: the diameter of a lens. The aperture is marked on a lens in centimeters, millimeters or inches. Older Nikkor lenses have markings in cm., later models in mm. and one (projection) Nikkor is known - Pro-Nikkor 3.5/4 inch - with markings in inches. The markings or aperture values are related to the focal length and maximum diameter. A lens with a marking f/1:1.4/50mm. indicates that the focal length is 50 mm. and the maximum (relative) aperture is 50 : 1.4 = 35.7, which is or should be the maximum diameter of the opening between the diaphragm blades (not the front lens) of that lens. The aperture on most lenses is marked with letters of an arithmetic series. On older lenses the so called German or ´9´-series (f/1.2 - 1.8 - 2.5 - 3.2 - 4.5 - 6.3 - 9 - 12.5 - 18 - 25 - 36 - 48) is engraved, while modern lenses (like all Nikkors) are engraved with the so called international or ´8´-series (f/0.7 - 1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 45 - 64 - 90). The latter series has been chosen as each higher or lower figure indicates a halving respectively a doubling of the amount of light which passes through the lens. Thus a 1.4/50 mm.-lens is two times faster than a 2/50mm.-lens.
´Faster´ is related to a lens with a relatively larger opening so one can choose a higher or faster shutter speed. In the 1950´s and 1960´s a mysterious race between lens manufacturers started. Many of them tried to dominate the other. In those days a lens with a maximum aperture of f/2.8 was quite normal. But some lens manufacturers presented lenses with maximum apertures of f/1.2 (Leitz), f/1.1 (Zunow & Nikon), f/1.0 (Leitz & Nikon) or even f/0.95 (Canon). Record holder still is Carl Zeiss with its Super Q-Gigantar 0.33/40mm. Nikon produced a Nikkor-N 1.1/50mm. (a f/1:1/5cm. was never marketed) for its rangefinder cameras, but never came with a faster lens for its SLR´s than the famous Noct-Nikkor 1.2/58mm. Also in telelenses amazing apertures were offered, like the Kilfitt 1.2/240mm. Most of those lenses were huge, heavy and extremely expensive. Film margin and sensor sensitivity has increased that far that very fast lenses are of no use. Autofocus sensors in most cameras can easily detect focus when using lenses with apertures up to f/5.6. And - more important - no exposure meter can detect the difference between e.g. f/1.2 and f/1.4.
The faster a lens, the more problems a lens designer has to tackle. Due to the refraction of light various aberrations and distortions will occur. Below are a few examples of (pin) cushion aberrations and the depth of field (DOF) of very fast lenses. The DOF of a lens like the Noct-Nikkor mentioned before at the closest distance is just a few millimeters. For some compositions interesting but in most cases leading to non-sharp images.
aberrations & distortions
Two (exaggerated) distortions (cushion) of a photographic lens
Around the feet of this (sea) gull depth of field (DOF) is clearly visible
More examples and explanations will follow soon!