Imaging Products

NIKKOR — The Thousand and One Nights - Glossary



The ideal image by lenses (especially photographic lenses), must fulfill three key conditions, namely,
1.) all light from the point object must be focused to a single point on the image plane (film),
2.) when the object plane is perpendicular to the optical axis, the image plane must also be perpendicular, and
3.) the object and the image (on the film) must closely resemble each other.
In reality, however, light refraction by the lens causes a variety of defects in the image, called aberration.
The five most common types in aberration are SEIDEL's five aberrations, which occur even with monochromatic (single-wave length) light, and two types of chromatic aberrations, which are caused by more than one frequency.
It is impossible to eliminate them all, but in the lens design process, they can be controlled and balanced to provide the best possible result for that lens and application.
This is handled by material (glass) selection, shape and positioning.

AI (Automatic Maximum Aperture Indexing ) System

An aperture-coupling device between a Nikkor lens and an exposure meter of a Nikon's SLR camera introduced by Nippon Kogaku K.K. (Nikon Co.) in 1977.
If AI system is introduced in both a camera (or a finder including an exposure meter such as a Photomic A finder DP-11 or a Photomic AS finder DP-12 for a Nikon F2) and a lens, as soon as the lens is set in the camera, the maximum aperture is automatically compensated and you can instantaneously enjoy a TTL metering at full aperture.
Accordingly, it becomes unnecessary to set the maximum aperture index manually or to confirm the maximum aperture by yourself.

When an AI Nikkor lens (Nikon Series E lens) having an exposure-meter-coupling guide on the aperture ring of the lens is coupled to an AI camera body, the maximum aperture is set to the camera body in connection with the exposure-meter-coupling guide.

Conventional System
AI System
  • Setting a connecting pin on a camera body
  • Setting an exposure-meter-coupling shoe on the aperture ring of the lens to f/5.6
  • Setting the lens at an index
  • Fitting the lens to the camera body
  • Setting the maximum aperture
  • Confirming the maximum aperture
  • Setting the lens at an index
  • Fitting the lens to the camera body

"AI" of the AI System is an abbreviation of "Automatic Maximum Aperture Indexing".
"AI" is liable to be misdescribed as "Ai" because its square logotype designed by Mr. KAMEKURA, Yusaku may be read as "Ai" as a result of his design treatment. However, "AI" is correct.

Analog Camera

It is big mistake that you call a camera using the silver-halide film (chemical film) as an "Analog Camera".
As if an analog video camera and a digital video camera are there in video cameras, an "Analog Camera" means an electronic video still camera using analogue recording. In Nikon's product, it corresponds to the Nikon Still Video Camera QV-1000C (released in 1988).
In an analog camera, a light entered through the lens is converted into an analog electric signal by an imaging device such as a CCD to be recorded as an analog signal without being converted into a digital signal like a digital camera.
Analog recording generally has a defect that the image quality becomes worse upon reproducing.

An electronic video still camera recording an A/D converted digital signal has been called a "Digital Video Still Camera", a "Digital Still Camera (DCS)", then a "Digital Camera". In Nikon's product, it corresponds to the Nikon Digital Still Camera E2/E2S (released in 1995) and those released after that.


It is a phenomenon in which light rays from an off-axis point form images at different positions along meridional and sagittal directions.
Astigmatism causes points to blur, degrading sharpness.
The visible phenomenon is a blurring of background and foreground (object points appear as linear or oval-shaped images).
It can be reduced but not eliminated by stopping down the lens.


Back focus

Back focal distance, meaning the distance (length) from the tip of the lens's furthest rear surface to the film surface where the image is focused.


Glue made from pine resin.
This glue is used to paste several lenses together.
Other than balsam, there are silicon-type, epoxy-type, and ultraviolet curable resin available these days.


A lens that resembles a symmetrical negative-positive-negative unit system wideangle lens.
It was designed by Dr. Ludwig BERTELE (1900-1985) when he was at a Wild-Heerbrugg (Swiss) , and is known with lenses such as Biogon 38mm, 53mm, 75mm, and 90mm ultrawideangle lens (all made in 1954), made by Zeiss (Germany) .


Chromatic Aberration

Chromatic Aberration is different from SEIDEL's five aberrations caused by monochromatic light, and can be broadly grouped into two types.
The first is longitudinal chromatic aberration, in which focal points vary with wavelength.
This type of aberration causes color smearing and a loss of sharpness in the center of the image.
It can be controlled by stopping down the lens.
The second type is lateral chromatic aberration, in which maginification varies with wavelength.
Lateral chromatic aberration is also known as transverse chromatic aberration or chromatic difference of magnification.
This is also visible, causing color smear and loss of sharpness for non-axial light.
It will not improve even if the lens is stopped down, and smear will increase in monochromatic film is used.
It can be reduced by the optimal combination of convex (positive) and concave (negagtive) lenses, and is greatly reduced by low-dispersion ED glass.

Close-range aberration fluctuation

Even when spherical aberration has been corrected, light flux from objects apart from the optical axis can cause coma.
The visible phenomenon is a point image on the picture trailing toward the exterior or the center of the image, like a comet, which is where the name comes from.
Coma spreading radially from the optical axis forms a teardrop-shaped flare, usually called a meridional coma flare.
A sagittal coma flare occurs concentrically, often for flying birds, forming a diamond-shaped flare.
Coma can be reduced by stopping down the lens.


Even when spherical aberration has been corrected, light flux from objects apart from the optical axis can cause coma.
The visible phenomenon is a point image on the picture trailing toward the exterior or the center of the image, like a comet, which is where the name comes from.
Coma spreading radially from the optical axis forms a teardrop-shaped flare, usually called a meridional coma flare.
A sagittal coma flare occurs concentrically, often for flying birds, forming a diamond-shaped flare.
Coma can be reduced by stopping down the lens.

Curvature of field

Unlike spherical aberration, coma or astigmatism, shows points as points, but the focal points do not match across the image center and periphery in image planes, so that the image is gradually bent out of shape toward the edges.
In a composition where light rays cross perpendicularly, for example, the image might be focused in the center but not at the edges, or vice-versa.
A phenomenon in which straight lines are not rendered perfectly straight in the picture.
Curvature of field can be improved but not eliminated by stopping down the lens.



Distortion, unlike spherical aberration, coma or astigmatism, shows points as points, but affects the shape of the image.
There are three (3) visible types, namely
1.) Barrel : Image deformation causes a rectangle to swell in the center, looking like a barrel (the corners of the rectangle are greater than 90 degrees).
2.) Pincushion : Image deformation causes the sides of a rectangle to move inward, forming a pincushion or star shape (the corners of the rectangle are less than 90 degrees).
3.) Combinations : Two types can also be combines.
Distortion cannot be corrected by stopping down the lens, but it can be improved by optical combination of positive and negative lens elements.



The first fisheye lens from Nippon Kogaku K. K. (now Nikon Corporation) was the 16mm f/8 Fisheye lens (picture angle: 180 degrees, equidistant projection, circular image), which was released in 1938. Here are the fisheye lenses that was released :

Fisheye-Nikkor 16.3mm f/8
180 degrees
(Equidistant Projection ; Circular Image)
5 elements in 4 groups
Fisheye-Nikkor 8mm f/8
180 degrees
(Equidistant Projection ; Circular Image)
5 elements in 4 groups
Fisheye-NIKKOR 7.5mm f/5.6
180 degrees
(Equidistant Projection, Circular Image)
9 elements in 6 groups
180 degrees
(Orthographic Projection ; Circular Image)
9 elements in 6 groups
Fisheye-NIKKOR 6mm f/5.6
220 degrees
(Equidistant Projection ; Circular Image)
9 elements in 6 groups
Fisheye-NIKKOR 8mm f/2.8
180 degrees
(Equidistant Projection ; Circular Image)
10 elements in 8 groups
Fisheye-NIKKOR 6mm f/2.8
220 degrees
(Equidistant Projection ; Circular Image)
12 elements in 9 groups
Fisheye-NIKKOR 16mm f/3.5
170 degrees
(Full-Frame, fisheye image)
8 elements in 5 groups
Fisheye-Nikkor 16mm f/2.8
180 degrees
(Full-Frame Fisheye Image)
8 elements in 5 groups
AF Fisheye Nikkor 16mm f/2.8D
180 degrees
(Full-Frame Fisheye Image)
8 elements in 5 groups
R-UW AF Fisheye NIKKOR 13mm f/2.8
170 degrees at underwater
(Full-Frame Fisheye Image)
8 elements in 5 groups
"Fisheye Type 20mm f/8"
153 degrees
(Full-Frame Fisheye Image)
3 elements in 2 groups
Fisheye Converter FC-E8
(For Nikon Digital Camera COOLPIX Series)
183 degrees
(Equidistant Projection ; Circular Image)
5 elements in 4 groups

Of these lenses, OP Fisheye-Nikkor 10mm f/5.6 was the first fisheye lens to adopt the Orthographic Projection optics.
Orthographic Projection lens projects the celestial image directly onto the film.
In the leaflet of a sales manual, which was distributed to major distributor in 1969, it read :

"When a picture is taken with this orthographic projection lens, the reflectance factor from the sky image can be easily obtained.
For example, in order to measure the brightness of the building district for a metropolitan project, you take the picture of the sky image from the road.
By measuring the volume of the sky image portion, then that becomes the brightness of the sky, and it can measure that area's the sky factor in numbers......".

This OP Fisheye-Nikkor 10mm f/5.6 is the world's first aspherical SLR lens.

Other than these lenses, there was a lens called "SAP-230 degrees Fisheye-NIKKOR" (6.2mm f/5.6 ; developed around 1968) which was not released for the public.
This lens was the world's first "EquiSolidangle Projection" (the volume of the image and the solidangle on the film surface are proportional) fisheye lens.
This lens also uses aspherical lens for correct projection.

SAP-230 degrees Fisheye-NIKKOR
230 degrees
(EquiSolidangle Projection ; Circular Image)
7 elements in 10 groups

Floating adjustment

When a photographic lens is focused at closed object, aberration fluctuation, in particular increase in curvature of field, is occurred. The effect is severe in asymmetrical lens types such as a retrofocus type.
In order to correct this effect, we developed findings that varying a particular lens separation caused only a change in curvature of field. It was a Floating adjustment.
This mechanism is constructed such that a plurality of lens groups are moved independently in accordance with focusing so that image plane becomes flat even when focusing at closed object.


Gaussian (Gauss-type) lens

It can be classified alongside the Triplet-type, the Tessar-type and the Sonnar-type, but it has a distinct lineage.
Unlike the Gaussian (Gauss-type) lens, the Triplet-type, Tessar-type and Sonnar-type lenses were named by either the inventor or the patent-holding company.
The Triplet-type lens was invented and named by Mr. Harold D. TAYLOR (1862-1943) (Cooke Company, Britain), the Tessar-type lens by Mr. Paul RUDOLPH (1858-1935) (Zeiss, Germany) and the Sonnar-type lens by Dr. Ludwig BERTELE (1900-1985) (Zeiss-Ikon, Germany).

The Gaussian (Gauss-type) lens was named by its inventors in honor of Dr. C.F. GAUSS (1777-1855), who in 1817 improved upon the "Fraunhofer" telescopic objective lens by adding a meniscus profile to its single convex (positive) and single concave (negative) lenses.

About 70 years later, in 1888, American Mr. Alvan G. CLARK (1832-1897) employed two sets of these Gauss telescopic objectives, one on either side of an aperture, and acquired a new patent.
Building on CLARK's design, in 1895, Zeiss' RUDOLPH used two lens cemented together rather than two concave (negative) lenses positioned around the center of the lens.
Known as the "Planar" lens, it used the curvature of the cemented interface to control chromatic aberration.
With four (4) groups and six (6) elements, it is the basis of the Gaussian design.
In 1920, a lens manufacturer at Taylor & Hobson, Britain, refined the Planar-type design. Mr. Horace W. LEE created the Opic-type lens, which featured six (6) elements in four (4) groups. (Gauss-type lens construction became popular for lenses with a large aperture and mid-range picture angle.)

Dr. GAUSS was not aware of the "Gauss-type lens," correctly known as the "Double Gauss type."
This lens offers superior compensation for both spherical and chromatic aberration.


Image flatness

Image flatness is a bit different from the curvature of field discussed in SEIDEL's five aberrations.
For photographic lenses, the image plane is the area where the image "rests" after "passing through" the aperture.
Here, flatness means that the individual image points are within a sufficiently low depth of focus variation.

Curvature of field basically describes the amount of surface curvature as defined by an image's individual chief rays.
As a result, the points making up the curvature of field and the optical energy peak will not match except when using extremely small apertures.
The difference becomes more pronounced as asymmetry between the upper and lower light flux of the chief ray increases, thereby causing the actual image plane to move farther from the field value curvature as the aperture approaches full-open.

Stopping down the aperture will increase the depth of focus.
Therefore, the importance of the resolved image surface (which defined the curvature of field) is less important, particularly with photographic lenses.


New types of optical glass

Development of eight new types of optical glass made with rare-earth elements such as lanthanum (La) and thorium (Th) in Japan (Nippon) began in June 1951, a joint effort by the five Japanese companies : Chiyoda Optical (now Minolta Co., Ltd.), Fuji Photo Film Co. Ltd., Konishiroku Photo Industries (now Konika Corporation) Ohara Optical Glass (now Ohara Inc.), and Nippon Kogaku K.K. (now Nikon Corporation).

In September 1951, Nippon Kogaku received a grant of 10.5 million Japanese Yen for industrial testing related to the manufacture of these new types of optical glass.
By November 1953, tests by Nippon Kogaku were completed for LaK1 (lanthanum crown); LaK3 and KF8 (crown flint); LLF (ultra-light flint); F16 (flint); and FK6 (chlorine-silicon crown). Ohara Optical Glass had concluded tests on LaK2 (lanthanum crown), as had Fuji Photo Film on BaSF8 (barium flint).

Contributing engineers met a total of 29 times. After testing was finished, a variety of new photographic lenses using the newly developed glasses were introduced by these manufacturers, demonstrating the significance of this wide-ranging R&D effort.


Ohi Plant (Current Ohi Plant 101 Building)

It was built in 1933. It is a five-story steel-framed concrete building with a basement.
It is well known even from the pre-W.W.II period for its international-style architecture, which is compared to that of Tokyo Central Post Office (Marunouchi 2-chome, Chiyoda-ku, Tokyo).

The work of the architect, Mr. YAMASHITA Toshiro, can be found at Roppongi 7-chome in Minato-ku, Tokyo (Western-style houses with a rotary at public area. The houses are rented and it belongs to Machida Douzoku Corporation (1935)).

Since 1959, Japanese government has imposed legal control of newly founding or increasing a factory (or university) with a certain area or more in a whole wards in Tokyo metropolitan area, Kawasaki-City and Yokohama-City, which correspond to Keihin industrial area.
Accordingly, the building has not been able to be rebuilt on a large scale since then.
Camera production facilities previously set in the building were moved to plants locating outside of metropolitan area one after another (ex. Mito, Sendai etc.).

By the way, the oldest building in Ohi Plant is the 153 Building which was built in 1931.



Here, the term "power" is used for refraction.


Ray Tracing Calculation

The lens is designed by the combination of the basic lens structure (the arrangement of concave (negative) and convex (positive) lens, position of the aperture, etc.) and the (refractive index of) optical lens.
After that, it makes a calculation by tracking (plotting) the ray emitted from one point of the subject, which goes through the lens and form the image.
The ray tracing calculation is tried out over and over by changing the circumstances (for example, by changing size of the penetrating angle of the ray emitted from the subject, distance between the subject, the wavelength of the ray, size of the aperture, etc.).
It tries to achieve optimal answer from the feedback received by adjusting the lens's refractive index and the using different optical lenses.

Though the computer does all the tracing calculation these days, it used to be a manual calculator.
And even before that, an abacus and logarithmic table was used (and calculated only by hand before that).

There are more ray tracing calculation needed for a zoom lens when compared with single focal length lens.

Retrofocus-type (wideangle) lens

It is a lens which has the principal point behind the rear part of the entire lens.
The design is like the reverse of a telephoto lens (thus called "retro"), and since the back focus (back focal distance) can be obtained longer than the focal length, it is used mostly for SLR wideangle lens.
Compared to symmetrical wideangle lens, the brightness of the edge of the image field is great, but the distortion is bigger.
From the outside, the front lens element is large, and when looking at the aperture blade from the rear of the lens, the aperture blade appears larger when seen from the front.


SEIDEL's five aberrations

The five (5) monochromatic aberrations analyzed by SEIDEL in Germany, in 1856 :
1.) spherical aberration,
2.) coma,
3.) astigmatism,
4.) curvature of field and
5.) distortion.

Sonnar-type lens

It is a lens type invented by Dr. Ludwig BERTELE (1900-1985), a famous designer at Zeiss of Germany.
It is regarded as basically a combination of the Ernostar and Tessar lens types.
Because it can be made with large diameters, and little glass-air surfaces, this type of lens was the subject of considerable R&D before coating technology developed.
The Sonnar lenses used as standard high speed (large-diameter) products offer short barrel lengths due to telephoto lens type, and less saggital coma flare than Gaussian (Gauss-type) lenses.
The design method used to reduce aberration, however, was quite complex, making them difficult to manufacture, and the close-range aberration fluctuation was large.
Then technology is carried on in 105 to 135 mm lenses for 35mm(135) format SLR cameras.

Spherical Aberration

Most lenses use spherical surfaces (as opposed to aspherical surfaces), so that light flux parallel to potical axis (imaged in the center of the image area, basically) does not focus on a single point in the focal plane (on the film).
This is spherical aberration. It appears a halo, blur and loss of sharpness.
It becomes more common at high aperture lens, and can be reduced by stopping down the lens.
It can also be reduced by the optimal combination of positive and negative lenses.



The photographic lens Barrel is cylindrical style, so that rays outside the optical axis will be cut off, partially or completely, by the barrel or lens edge.
This is called vignetting. If you look in from the front of the lens, and tilting the lens, you will be able to see the blockage clearly.
The aperture, with a polygonal shape, is visible on all lenses except retrofocus lenses and negative lenses (including zooms).
In retrofocus lenses, the aperture widens as you tilt the lens (peripheral image is relatively bright).
In addition to reducing light intensity at peripheral, vignetting is also closely related to out focus image.


WAKIMOTO, Zenji (1924-1996)

Born in Hyogo-Ken, Japan (Nippon). Studied at University of Tokyo under Professor OANA, Jun, and joined Nippon Kogaku K.K. (present Nikon Corporation) in 1948.
He is one of the founders of Nikkor lens for "S"-series and F-series.
He also designed Micro-NIKKOR lens (lens for precise duplication) and Ultramicro-Nikkor lens (lens for high-precision exposure system, such as ICs and LSIs).
He was a director and became an advisor until 1993.
He received "Purple Ribbon Medal" from the Emperor in Spring 1983. He died on October 5th, 1996.


Xenotar-type lens

The first Xenotar-type lens, "Xenotar 80mm f/2.8", was first released in 1954 as a medium-aperture (around f/2.8) standard lens for medium-size film format cameras by a German manufacturer, Schnider.
This lens is a modified version of a Gaussian (Gauss-type) lens (this lens was made after Gaussian(Gauss-type) lens was introduced).
The cemented lens at the rear is composed of just one concave (positive) lens, therefore it performs well as a medium-aperture, medium angle-of-field lens.

There was also a lens called "Biometar" which was released around the same time by another German manufacturer, Carl Zeiss Jena.


ZUNOW 5cm f/1.1

This lens first appeared in 1953, developed by Mr. HAMANO, Michisaburo, who had come to Nippon Kogaku K.K. from the navy and would later move on to Teikoku Optical Industries.
The ZUNOW 5cm f/1.1 has five (5) groups and nine (9) lenses, with a Sonnar-type M39 mount (39mm diameter, 1/26-inch thread screw) and Nikon "S" mount.

In 1955, Mr. KUNIMI, Kenji who had come from Nippon Kogaku K.K., and Mr. FUJIOKA, Yoshisato, who had come from Yashima Kogaku K.K., improved upon this design using new optical glass in a four (4)-group, nine (9)-lens structure. Subsequent revisions yielded the 5cm f/1.3 lens.


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